Handbook of Neurosurgery 8th Edition-4

Prim ary Intracranial Anom alies 249 Table 15.1 Distribution of arachnoid cysts3 % Locat ion 49% sylvian fissure 11% CPA 10% su p ra co llicu la r 9% ve rm ian 9% sellar & suprasellar 5% in t e rh e m isp h e ric 4% cerebral convexit y 3% clival Table 15.2 Typical presentations of arachnoid cysts Middle fossa cyst s Suprasellar cyst s wit h hydroce- Diffuse supra- or infratentorial cyst s p h a lu s wit h hydrocephalus seizures intracranial hypertension intracranial hypertension headache craniom egaly cran io m e g aly hem iparesis developmental delay developm ental delay visual loss precocious pubert y bobble-head doll syndrom e a) due to h em orrh age (in to cyst or subdural com par tm en t): m iddle fossa cysts are n otorious for 15 h em orrh age due to tearin g of bridgin g vein s. Som e sports organ izat ion s do n ot allow partici- pation in con tact sports for th ese pat ien ts b) due to rupture of the cyst 4. as a focal protrusion of th e sku ll 5. w ith focal sign s/sym ptom s of a space occupyin g lesion 6. in ciden tal fin ding discovered durin g evaluation for un related con dit ion 7. suprasellar cysts m ay addition ally presen t w ith 5: a) hydrocephalus (probably due to com pression of the third ven tricle) b) en docrin e sym ptom s: occurs in up to 60%. In cludes precocious pubert y c) h ead bobbin g (th e so-called “bobble-h ead doll syn drom e”6): con sidered suggest ive of supra- sellar cysts, but occurs in as few as 10% d) visual im pairm ent 15.1.5 Evaluat ion General inform at ion Routin e evaluation w ith CT or MRI is usually satisfactory. Furt h er evaluation w ith CSF con trast or flow studies (cistern ogram s, ven triculogram s…) are on ly occasion ally n ecessar y for th e diagn osis of m idlin e suprasellar an d posterior fossa lesion s4; for Di eren tial diagn osis, see In tracran ial cysts (p.1374); see Fig. 15.1 for th e classification sch em e of Galassi et al for m iddle fossa cysts. CT s ca n Sm ooth bordered n on -calcified extraparen chym al cystic m ass w ith den sit y sim ilar to CSF an d n o en - h an cem en t w ith IV con trast. Expan sion of n earby bon e by rem odellin g is usually seen , con firm ing th eir ch ron ic n at ure. Often associated w ith ven t riculom egaly (in 64% of supraten torial an d 80% of in fraten torial cysts). Convexit y or m iddle fossa cysts exert m ass e ect on adjacen t brain an d m ay com press ipsilateral lateral ven tr icle an d cause m idlin e sh ift . Suprasellar, quadrigem in al plate, an d m idlin e posterior-fos- sa cysts m ay com press th e th ird an d fourth ven t ricle an d cause hydrocephalus by obstruct in g th e foram in a of Mon ro or th e Sylvian aqueduct .

250 Developm ental Anom alies Fig. 15.1 CT Classification of Sylvian fissure arachnoid cysts.7 Type I: small, biconvex, located in anterior temporal tip. No mass e ect. Comm unicates with subarachnoid space on water-soluble contrast CT cisternogram (WS-CTC). Type II: involves proximal and interm ediate segments of Sylvian fissure. Completely open insula gives rectangular shape. Partial com munication on WS-CTC. Type III: involves entire Sylvian fissure. Marked midline shift. Bony expansion of m iddle fossa (elevation of lesser wing of sphenoid, out ward expansion of squam ous tem poral bone). Minim al com munication on WS-CTC. Surgical treatm ent usually does not result in total reexpansion of brain (may approach t ype II lesion). MRI Better th an CT in di eren tiating th e CSF con tain ed in arach noid cysts from th e fluid of n eoplastic cysts. May also show cyst w alls. Cist ernogram s and/or vent riculogram s Usin g eith er iodin ated con trast or radion uclide tracers. Variable rate of opacificat ion h as resulted in di cult y correlatin g results w ith operative fin din gs. Som e cysts are act ually divert icula, an d m ay fill w ith radiotracer or contrast. 15.1.6 Treat m ent General inform at ion Many (but n ot all) auth ors recom m en d n ot treatin g arach n oid cysts th at do n ot cause m ass e ect or sym ptom s, regardless of th eir size an d location . For in ciden tally discovered arach n oid cyst in an 1 5 adult n ot con sidered for surgery: a sin gle follow -up im agin g study in 6–8 m on th s is usually adequate to rule-out any ch anges (sin ce th ey m ay grow in size). Subsequen t st udies m ay be don e if con cern in g sym ptom s develop. Pediatric patien ts m ay n eed to be follow ed un til adulth ood. Treat m ent considerat ions for cyst s (excluding suprasellar cyst s) Surgical treatm en t opt ion s are sum m arized in Table 15.3. Cyst shunt ing Probably th e best overall t reatm en t. For sh un ting in to periton eum , use a low pressure valve. If th ere is con curren t ven triculom egaly, on e m ay sim ultan eously place a ven tricular sh un t (e.g. th rough a “Y” con n ector). Ult rasoun d, ven triculoscope, or im age guidan ce m ay assist in locat in g suprasellar cysts. Sh unt in g of m iddle fossa ACs m ay also be accom plish ed th rough th e lateral ven tr icle, th us sh un tin g both com partm en ts.9 NB: in run n ing th e distal sh un t t ubin g from th e m iddle fossa, it sh ould be routed beh in d th e ear (do n ot t un n el in fron t of ear to avoid injur y to facial n er ve – if th is an terior route is un avoidable, it m ay h elp to solicit th e ser vices of a plastic surgeon to h elp avoid th e facial n er ve). Treat m ent of Suprasellar cyst s Th ese cysts presen t w ith som e un ique treatm en ts option s w h ich in clude: ● transcallosal cystectom y10

Prim ary Intracranial Anom alies 251 Table 15.3 Surgical treatment options for arachnoid cysts Pr o ce d u r e Advant ages Disadvant ages drainage by needle aspira- ● sim ple ● high rate of recurrence of cyst and tion or burr hole evacuation ● quick neurologic deficit craniotomy, excising cyst ● permits direct inspection of cyst (m ay ● subsequent scarring may block wall and fenestrating it into help with diagnosis) fenestration allowing reaccum ula- basal cisterns tion of cyst ● loculated cysts (rare) treated m ore e ffe ct ive ly ● flow through subarachnoid space m ay be deficient; many patients ● avoids perm anent shunt (in some develop shunt dependency post-op cases) ● significant morbidit y and m ortalit y ● allows visualization of bridging vessels (m ay be due to abrupt decom - (small advantage) p re ssio n ) endoscopic cyst fenestration ● as above ● as above through a burr hole8 shunting of cyst into perito- ● definitive treatment ● patient becom es “shunt depend- neum or into vascular sys- ● low m orbidit y/m ortalit y ent” tem ● low rate of recurrence ● risk of infection of foreign body (sh u n t ) ● percutan eous ven triculo-cystostom y: procedure of ch oice of Pierre-Kah n et al.5 Perform ed via a param edian coron al burr h ole th rough th e lateral ven t ricle an d foram en of Mon ro (m ay be facili- tated by using a ventriculoscope8) ● subfron tal approach (for fen estrat ion or rem oval): dan gerous an d in e ect ive5 ventricular drainage is ine ect ive (actually prom otes cyst enlargem en t) and sh ould n ot be rou- t in ely con sidered 15.1.7 Out com e Even follow in g successful treatm en t a port ion of th e cyst m ay rem ain due to th e rem odelin g of th e bon e an d ch ronic sh ift of brain con ten ts. Hydroceph alus m ay develop follow in g t reatm en t. En docri- n opath ies ten d to persist even after successful t reatm en t of suprasellar cysts. 15.2 Craniofacial developm ent 15 15.2.1 Norm al developm ent Fo n t a n e lle s Anterior fonta nelle: th e largest fon tan elle. Diam on d sh aped, 4 cm (AP) × 2.5 cm (tran sverse) at birth . Norm ally closes by age 2.5 yrs. Poster ior fonta nelle :trian gular. Norm ally closes by age 2–3 m os. Sphenoid an d ma stoid fonta nelles: sm all, irregular. Norm ally, form er closes by age 2–3 m os, latter by age 1 yr. Cranial vault Grow th : largely determ in ed by grow th of brain . 90%of adult h ead size is ach ieved by age 1 yr; 95% by age 6 yrs. Grow th essen tially ceases at age 7 yrs. By en d of 2n d yr, bon es h ave in terlocked at sutures an d furth er grow th occurs by accret ion an d absorption . Skull is un ilam in ar at birth . Diplöe appear by 4th yr an d reach a m axim um by age 35 yrs (w h en diploic vein s form ). Mastoid process: form at ion com m en ces by age 2 yrs, air cell form ation occurs durin g 6th yr.

252 Developm ental Anom alies 15.2.2 Craniosynost osis Ge n e r a l Origin ally called cran iosten osis. In ciden ce: ≈ 0.6/1000 live bir th s. Prim arily a pren atal deform it y, postn atal cran iosyn ostosis (CSO) occurs un com m on ly (post n atal causes con sist prim arily of position al alteration s w h ich m ay n ot represen t true syn ostosis). CSO is rarely associated w ith hydroceph alus (HCP).11 Th e assert ion th at CSO m ay follow CSF sh un tin g for HCP is un proven . Oth er causes for failure of n orm al skull grow th in clude lack of brain grow th due to any of th e causes of arrested developm en t of the cerebral h em isph eres (lissen ceph aly, m icropolygy- ria, som e cases of hydran en ceph aly…). Treatm en t is usually surgical. In m ost in stances, th e in dicat ion for surger y is for cosm esis an d to preven t th e severe psych ological e ects of h avin g a disfigurin g deform it y. How ever, w ith m ultiple CSO, brain grow th m ay be im peded by th e unyieldin g sku ll. Also, ICP m ay be path ologically elevated, an d alth ough th is is m ore com m on in m ultiple CSO,12 elevated ICP occurs in ≈ 11% of cases w ith a sin gle stenotic suture. Coron al syn ostosis can cause am blyopia. Most cases of sin gle suture involve- m en t can be t reated w ith lin ear excision of th e suture. Involvem en t of m ult iple sutures or th e skull base usually requires th e com bin ed e orts of a n eurosurgeon an d cran iofacial surgeon , an d m ay n eed to be staged in som e cases. Risks of surgery in clude: blood loss, seizures, stroke. Dia g n o s is Many cases of “syn ostosis” are really due to position al flatten ing (e.g. “lazy lam bdoid”, see below ). If this is suspected, instruct parents to keep head o of flatten ed area and recheck patient in 6–8 w eeks: if it w as position al, it sh ould be im proved, if it w as CSO th en it usually declares itself. Th e diagn osis of CSO m ay be aided by: 1. palpation of a bony prom inence over th e suspected synostotic suture (exception : lam bdoidal syn ostosis, see below ) 2. gen tle firm pressure w ith th e th um bs fails to cause relative m ovem en t of th e bon es on eith er side of the suture 3. plain skull x-rays: a) lack of n orm al lucency in center of suture. Som e cases w ith n orm al x-ray appearan ce of th e suture (even on CT) m ay be due to focal bony spicule form ation 13 b) beaten copper calvaria (p. 254), sut ural diastasis an d erosion of th e sella m ay be seen in cases of in creased ICP14 4. CT scan : a) h elps dem on strate cran ial con tour b) m ay sh ow th icken in g an d/or ridgin g at th e site of syn ostosis c) w ill dem onstrate hydrocephalus if present d) m ay sh ow expan sion of th e fron tal subarach n oid space15 e) th ree-dim en sional CT m ay h elp better visualize abn orm alit ies 1 5 5. in question able cases, a tech n etium bon e scan can be perform ed16: a) th ere is little isotope uptake by any of th e cran ial sutures in th e first w eeks of life b) in prem aturely closing sutures, in creased activity com pared to th e other (norm al) sutures w ill be demonstrated c) in com pletely closed sutures, no uptake w ill be dem onstrated 6. MRI: usually reser ved for cases w ith associated in t racran ial abn orm alit ies. Often n ot as h elpful as CT 7. m easurem en ts, such as occipito-fron tal-circum feren ce m ay n ot be abn orm al even in th e face of a deform ed sku ll sh ape Increased ICP Eviden ce of in creased ICP in th e n ew born w ith cran iosyn ostosis in clude: 1. radiograph ic sign s (on plain skull x-ray or CT, see above) 2. failure of calvarial grow th (un like th e n on -synostotic sku ll w h ere in creased ICP causes m acrocra- n ia in th e n ew born , h ere it is th e syn ostosis th at causes th e in creased ICP an d lack of skull grow th ) 3. papilledem a 4. developm en tal delay

Prim ary Intracranial Anom alies 253 Types of craniosynost osis Sagit tal synostosis General inform ation Th e m ost com m on CSO a ect in g a single suture; 80% m ale. Results in dolich oceph aly or scaph oce- ph aly (boat sh aped skull) w ith fron tal bossing, prom in en t occiput , palpable keel-like sagittal ridge. OFC rem ain s close to n orm al, but th e biparietal diam eter is m arkedly reduced. As m any as 44% of patien ts w ith n on syn drom ic sagittal syn ostosis h ave elevated ICP.17 Surgical t reat m ent Skin in cision m ay be lon git udin al or tran sverse. A lin ear “strip” cran iectom y is perform ed, excising th e sagittal suture from th e coron al to th e lam bdoid suture, preferably w ith in th e first 3–6 m on th s of life. Th e w idth of th e strip sh ould be at least 3 cm , n o proof exists th at in terposing artificial sub- stan ces (e.g. silast ic sh eetin g over th e exposed edges of th e parietal bon e) retards th e recurren ce of syn ostosis. Great care is taken to avoid dural laceration w ith poten tial injur y to th e un derlying supe- rior sagit tal sin us. Th e ch ild is follow ed an d reoperated if fusion recurs before 6 m on th s age. After ≈ 1 yr age, m ore exten sive cran ial rem odellin g is usually required. Coronal synostosis General inform ation Accoun ts for 18% of CSO, m ore com m on in fem ales. In Crouzon’s syn drom e th is is accom pan ied by abn orm alit ies of sph en oid, orbital an d facial bon es (hypoplasia of m idface), an d in Apert’s syn drom e is accom pan ied by syn dact yly.18 Un ilateral coron al CSO → plagioceph aly w ith foreh ead on a ected side flatten ed or con cave above eye (n orm al side falsely appears to bulge abn orm ally), supra-orbital m argin h igh er th an n orm al side (on skull x-ray → h arlequin eye sign ). Th e orbit rotates out on th e abn orm al side, an d can produce am blyopia. W ith out t reatm en t, flattened ch eeks develop an d th e n ose deviates to th e n orm al side (root of n ose ten ds to rotate tow ards deform ity). Bilateral coron al CSO (usually in cran iofacial dysm orph ism w ith m ult iple suture CSO, e.g. Apert’s) → brachyceph aly w ith broad, flatten ed foreh ead (acroceph aly). W h en com bin ed w ith prem ature clo- sure of fron tosph en oidal an d frontoeth m oidal sutures, results in foresh orten ed an terior fossa w ith m axillar y hypoplasia, sh allow orbits, progressive proptosis. Surgical t reat m ent Sim ple st rip cran iectom y of th e involved sut ure h as been used, often w ith excellen t cosm etic result . How ever, som e argum en t th at th is m ay n ot be adequate h as been presen ted. Th erefore, a m ore cur- ren t recom m en dation is to do fron tal cran iotom y (un i- or bi-lateral) w ith lateral can th al advan ce- m ent by takin g o orbital bar. Metopic synostosis 15 At birth , th e fron tal bon e con sists of t w o h alves separated by th e fron tal or m etopic sut ure. Abn or- m al closure results in a poin ted foreh ead w ith a m idlin e ridge (tr igon oceph aly). Many of th ese h ave a 19p ch rom osom e abnorm alit y an d are retarded. Lam bdoid synostosis Epidem iology Lon g con sidered a clin ical rarit y w ith a reported in ciden ce ran ge 1–9%of CSO,19 recen t reports sug- gest a h igh er in ciden ce of 10–20%20 w h ich m ay be due to an act ual in creased in ciden ce, or sim ply to in creased aw aren ess or ch anging diagn ostic criteria. More com m on in m ales (m ale:fem ale = 4:1), an d th e righ t side is involved in 70%of cases. Usually presen ts bet w een 3–18 m on th s of age, but m ay be seen as early as 1–2 m onths of age. Con troversy exists regarding th e act ual criteria for th is con dition , an d som e auth ors di eren tiate betw een th ose cases w h ich appear to h ave a prim ar y abn orm alit y of th e lam bdoid suture from th ose w h ich m ay be due to position al flatten ing, th e so-called “lazy lam bdoid.” Oth ers do n ot m ake th is dist in ct ion , an d som etim es refer to th e con dition as occipital plagioceph aly to avoid th e n eed to im plicate abn orm alit ies of th e lam bdoid sut ure. Position al flatten ing (or m olding) m ay be produced by: 1. decreased m obilit y: pat ien ts w h o con stan tly lie supin e w ith th e h ead to th e sam e side, e.g. cere- bral palsy, m en tal retardat ion , prem aturit y, ch ron ic illn ess 2. abn orm al post ures: congenita l torticollis ,21 congen ital disorders of th e cer vical spin e

254 Developm ental Anom alies 3. intentional position in g: trend since 1992 to place new borns in a supine sleeping position to reduce th e risk of sudden in fan t death syn drom e (SIDS),22 som etim es w ith a foam w edge to t ilt the child to on e side to reduce the risk of aspiration 4. in t rauterin e etiologies23: in t rauterin e crow din g (e.g. from m ultiparous birth s or large fetal size), uterine anom alies Clinical findings Flatten in g of th e occiput . May be un ilateral or bilateral. If un ilateral, it is som etim es term ed lam b- doid plagioceph aly w h ich w h en severe also produces bulgin g of th e ipsilateral foreh ead resultin g in a “rh om boid” skull w ith th e ipsilateral ear located an terior an d in ferior to th e con tralateral ear. Th e con tralateral orbit an d foreh ead m ay also be flattened. Th is m ay be con fused w ith h em ifacial m icro- som ia or w ith plagioceph aly seen in un ilateral coron al cran iosyn ostosis. Bilateral lam bdoid syn osto- sis produces brachyceph aly w ith both ears displaced an teriorly an d in feriorly.19 Unlike th e palpable ridge of sagit tal or coron al syn ostosis, an indenta tion m ay be palpated alon g th e syn ostot ic lam bdoid suture (alth ough a perisut ural ridge m ay be foun d in som e). Diagnostic evaluation Th e physical exam is th e m ost im por tan t aspect of diagn osis. Skull x-ray m ay h elp di eren tiate (see below ). If th e skull x-ray is equivocal, preven t th e in fan t from layin g on th e a ected side for several w eeks. A bon e scan sh ould be obtain ed if n o im provem en t occurs (see below ). In defin ite cases of syn ostosis, an d for som e cases of refractory position al flatten ing (w h ich usually corrects w ith tim e, but m ay take up to 2 years) surgical treatm ent m ay be in dicated. Sku ll x-ray: Show s a sclerotic m argin along one edge of the lam bdoid suture in 70%of cases. Local “beaten copper cranium ” (BCC) occasionally m ay be seen due to inden tation s in the bone from under- lying gyri w hich m ay be due to locally increased ICP. BCC produces a ch aracteristic m ottled appear- ance of the bon e w ith lucencies of varying depth h aving round an d poorly m arginated edges. BCC correlates w ith generalized ↑ ICP only w hen it is seen w ith sellar erosion and sutural diastasis.14 CT scan : Bon e w in dow s m ay sh ow eroded or th in n ed in n er table in th e occipital region in 15– 20% of cases,20 > 95% are on th e side of th e involvem en t. Th e sut ure m ay appear closed. Brain w in - dow s sh ow paren chym al brain abn orm alit ies in < 2%: h eterotopias, hydroceph alus, agen esis of th e corpus callosum ; but ≈ 70% w ill h ave sign ifican t expan sion of th e fron tal subarach n oid space (m ay be seen in syn ostosis of oth er sutures, see above). Bon e scan : Isotope uptake in th e lam bdoid suture in creases during th e first year, w ith a peak at 3 m on th s of age24 (follow in g th e usual in act ivity of th e first w eeks of life). Th e fin dings w ith syn ostosis are th ose t ypical for CSO (p. 252). Treat m ent Early surgical t reatm en t is in dicated in cases w ith severe cran iofacial disfigurem en t or th ose w ith evidence of in creased ICP. Oth erw ise, ch ildren m ay be m an aged n on surgically for 3–6 m on th s. Th e m ajorit y of cases w ill rem ain static or w ill im prove w ith tim e and sim ple nonsurgical inter vention. 1 5 Approxim ately 15%w ill con tin ue to develop a sign ifican t cosm etic deform ity. Non surgical m anagem ent25: Alth ough im provem en t can usually be attain ed, som e degree of perm an en t disfigurem en t is frequen t. Reposition in g w ill be e ective in ≈ 85%of cases. Patien ts are placed on th e un a ected side or on th e abdom en . In fan ts w ith occipital flatten ing from tort icollis sh ould h ave aggressive ph ysical th er- apy an d resolution sh ould be observed w ithin 3–6 m on ths. More severe involvem ent m ay be treated w ith a trial of m olding h elm ets26 (how ever, no con - trolled study has proven the e cacy). Surgical treatm en t: Required in on ly ≈ 20%of cases. Th e ideal age for surgery is betw een 6 an d 18 m on th s. Th e pat ien t is position ed pron e on a w ell-padded cerebellar h eadrest (th e face sh ould be lifted an d gen tly m as- saged every ≈ 30 m in utes by th e anesthesiologist to preven t pressure injuries). Surgical option s ran ge from sim ple un ilateral cran iectom y of th e suture to elaborate recon struc- t ion by a cran iofacial team . Lin ear cran iectom y exten ds from th e sagittal suture to th e asterion is often adequate for patien ts ≤ 12 w eeks of age w ith out severe disfigurem en t. Great care is taken to avoid dural laceration n ear th e asterion w h ich is in th e region of th e tran sverse sin us. Th e excised suture dem on strates an inter na l ridge. Better results are obtain ed w ith earlier surger y, m ore radical surger y m ay be n ecessar y after the age of 6 m onths. Average blood loss for un com plicated cases is 100–200 m l an d th erefore tran sfusion is often r e q u ir e d .

Prim ary Intracranial Anom alies 255 Multiple synostoses Fusion of m any or all cran ial sutures → oxyceph aly (tow er skull w ith un developed sin uses an d sh al- low orbits). Th ese patien ts h ave elevated ICP. Craniofacial dysm orphic syndrom es Over 50 syn drom es h ave been described, Table 15.4, sh ow s a few selected on es. A n um ber of cran iosyn ostosis syn drom es are due to m utation s in th e FGFR (fibroblast grow th fac- tor receptor) gen es. FGFR gen e-related cran iosyn ostosis syn drom es in clude som e classic syn drom es (Apert , Crouzon , Pfei er…) as w ell as several n ew er en tit ies (Beare-Steven son , Muen ke, Jackson - Weiss syn drom es). All exh ibit autosom al dom in an t in h eritan ce. 15.2.3 Encephalocele General inform at ion Cran ium bifidum is a defect in th e fusion of th e cran ial bon e, it occurs in th e m idlin e, an d is m ost com m on in th e occipital region . If m en in ges an d CSF h ern iate th rough th e defect , it is called a m en in gocele. If m en in ges an d cerebral t issue protrude, it is called an en cephalocele. En ceph alocele AKA ceph alocele is an exten sion of in tracran ial struct ures outside of th e n orm al con fin es of th e skull. On e case w as seen for ever y five cases of spin al m yelom en ingoceles.28 A n asal polypoid m ass in a newbor n sh ould be con sidered an en cephalocele un til proven oth erw ise. See also Di eren tial diagn osis (p.1388). Classificat ion 15 System based on Suw anw ela an d Suw anw ela29: 1. occipital: often involves vascular st ruct ures 2. cran ial vault: com prises ≈ 80%of en ceph aloceles in Western h em isph ere a) in terfron tal b) an terior fon tan elle c) in terparietal: often involves vascular st ructures d) temporal e) posterior fon tan elle 3. fron to-eth m oidal: AKA sin cipital; 15%of enceph aloceles; extern al open in g in to face in on e of th e follow in g 3 region s: a) n asofron tal: extern al defect in th e n asion b) n aso-eth m oidal: defect bet w een n asal bon e an d n asal cartilage c) n aso-orbital: defect in th e an tero-in ferior por t ion of m edial orbital w all 4. basal: 1.5%of en ceph aloceles; (see below ) a) tran seth m oidal: protrudes in to n asal cavit y th rough defect in cribriform plate b) spheno-ethm oidal: protrudes into posterior nasal cavity Table 15.4 Selected craniofacial dysm orphic syndrom es (m odified27 (p 123–4)) Syndrom e Ge n e t ics Craniofacial findings Associat ed findings Sporadic Inherit ed Crouzon (craniofacial dysostosis) yes (25%) FGFR AD CSO of coronal & basal HCP rare skull sutures, m axillary hypoplasia, shallow or- bits, proptosis Apert (acrocephalosyndact yly) yes (95%) FGFR AD sam e as Crouzon syndact yly of digits 2,3,4; shortened UE, HCP common Kleeblat tschadel yes AD CSO with trilobular skull isolated, or with Apert’s or thanato- phoric dwarfism aAbbreviations: AD = autosom al dom inant; FGFR= fibroblast growth factor receptor gene-related; CSO = cranio- synostosis; HCP = hydrocephalus; UE= upper extrem ities

256 Developm ental Anom alies c) tran ssphenoidal: protrudes into sphenoid sinus or nasoph arynx through patent craniophar- yn geal can al (foram en cecum ) d) fron to-sph en oidal or sph en o-orbital: protrudes in to orbit th rough superior orbital fissure 5. posterior fossa: usually con tain s cerebellar tissue an d ven tr icular com pon en t Basal encephalocele Th e on ly group th at does n ot produce a visible soft t issue m ass. May presen t as CSF leak or recurren t m en in gitis. May be associated w ith oth er cran iofacial deform ities, in cludin g: cleft lip, bifid n ose, optic-n er ve dysplasia, colobom a an d m icroph th alm ia, hypoth alam ic-pitu itary dysfun ct ion . In ien ceph aly is ch aracterized by defects aroun d th e foram en m agn um , rach isch isis an d retrocollis. Most are stillborn , som e survive up to age 17. Et iology Tw o m ain th eories: 1. arrested closure of n orm al con fin in g t issue allow s h ern iation th rough persisten t defect 2. early outgrow th of n eural tissue preven ts n orm al closure of cran ial coverin gs Treat m ent Occipit al encephalocele Surgical excision of th e sac an d its con ten ts w ith w ater-tigh t dural closure. It m ust be kept in m in d th at vascular struct ures are often in cluded in th e sac. Hydroceph alus is often presen t an d m ay n eed to be t reated separately. Basal encephalocele Caution : a t ran sn asal approach to a basal en ceph alocele (even for biopsy alon e) m ay be fraugh t w ith in tracran ial h em orrh age, m en in gitis, or persisten t CSF leak. Usually a com bin ed in tracran ial approach (w ith am putation of th e extracran ial m ass) an d tran sn asal approach is used. Out com e Occipit al encephalocele Th e progn osis is better in occipital m en in gocele th an in en ceph alocele. Th e progn osis is w orse if a sign ifican t am oun t cerebral tissue is presen t in th e sac, if th e ven tricles exten d in to th e sac, or if th ere is hydroceph alus. Less th an ≈ 5%of in fan ts w ith en ceph alocele develop n orm ally. 15.3 Dandy Walker m alform at ion 15 15.3.1 General inform at ion Defin ition : an en larged posterior fossa w ith com plete or part ial agen esis of th e cerebellar verm is an d cystic dilatation of th e fourth ven tricle w h ich is distorted an d en cased in a m em bran e. Th e an om aly w as first described by Dan dy & Blackfan in 1914, an d w as n am ed Dan dy Walker m alform a- t ion for t y years later by Ben da to ackn ow ledge Taggart an d Walker’s con tribution s in 1942.30 15.3.2 Di erent ial diagnosis Disorders w ith posterior fossa CSF collection s in clude31: 1. Dan dy Walker m alform ation (DW M) 2. Dan dy Walker varian t (DW V): verm ian hypoplasia an d cystic dilatation of th e fourth ven tricle, w ith out en largem en t of th e posterior fossa 3. persisten t Blake’s pouch cyst (BPC): tetraven t ricular hydroceph alus, com m un icatin g 4th ven tricle an d posterior fossa cyst, w ith or w ith out hypoplasia of both th e cerebellar verm is an d th e m edial aspects of th e cerebellar h em isph eres 4. retrocerebellar arach n oid cyst: an teriorly displaces th e 4th ven tricle an d cerebellum , w h ich can produce sign ifican t m ass e ect 5. Joubert’s syn drom e: absence or un derdevelopm en t of th e cerebellar verm is 6. m ega cistern a m agn a: en larged posterior fossa secon dar y to an en larged cistern a m agn a w ith a n orm al verm is an d fourth ven tr icle)

Prim ary Intracranial Anom alies 257 Di eren t iat in g feat u res: DW M an d DW V are di cult to dist in guish , an d m ay represent a con tin u- um of developm en tal an om alies th at are grouped togeth er as Dandy Walker com plex.32 Retrocerebellar arach n oid cysts an d BPCs m ay m im ic DW M, but th ese do not h ave verm ian agen - esis an d th e cyst does n ot open in to th e 4th ven t ricle. Th e position of th e ch oroid plexus of th e four th ven tricle is n orm al in arach n oid cysts, absen t in Dan dy Walker m alform at ion s, an d displaced in to th e superior cyst w all in BPC. An in trath ecal en h an ced CT scan (perform ed after in stillin g iodi- nated contrast into a ventricular catheter) would identify a m ega cisterna m agna w hich com m uni- cates w ith th e ven tricles, w h ile DW M an d m ost but n ot all arachn oid cysts do n ot. 15.3.3 Pat hophysiology Th e etiology of DW M is un kn ow n . Multiple un sat isfactory th eories h ave been aban don ed. DW M is likely due to dysem br yogen esis, secon dary to in sults of var ying severit y to th e cerebellum an d 4th ven tr icle. Th is results in agen esis of th e cerebellar verm is w ith a large posterior fossa cyst com m un i- catin g w ith an en larged 4th ven tr icle.32,30 Hydroceph alus occurs in 70–90%of cases, an d Dandy Walker m alform ation is presen t in 2–4%of all cases of hydroceph alus. 15.3.4 Risk fact ors and epidem iology Gestat ion al exposure to rubella, CMV, toxoplasm osis, w arfarin , alcoh ol, an d isotret in oin are th ough t to be predisposin g factors. Autosom al recessive in h eritan ce h as been iden tified in a few cases, but a gen et ic basis is lacking in m ost . In ciden ce: 1 per 25,000–35,000 live birth s.30 Male:fem ale=1:3. 15.3.5 Associat ed abnorm alit ies CNS abn orm alit ies in clude agen esis of th e corpus callosum in 17%,33 an d occipital en ceph alocele in 7%. Oth er fin din gs in clude h eterotopias, spin a bifida, syrin gom yelia, m icroceph aly, derm oid cysts, poren ceph aly, an d Klippel-Feil deform it y. Most h ave an en larged posterior fossa w ith elevation of th e torcular h eroph ili. Atresia of th e foram in a of Magen die an d Luschka m ay occur.34 System ic abn orm alit ies in clude33: facial abn orm alit ies (e.g. an giom as, cleft palates, m acroglossia, facial dysm orph ia), ocular abn orm alit ies (e.g. colobom a, retin al dysgen esis, m icroph th alm ia), an d cardiovascular an om alies (e.g. septal defects, paten t duct us arteriosus, aortic coarctation , dextrocar- dia). Note: be aw are of th e possibilit y of a cardiac abn orm alit y w h en con siderin g surger y on th ese p a t ie n t s. 15.3.6 Treat m ent 15 Early decom pression of ven t riculom egaly is recom m en ded to ach ieve m axim um cogn itive develop - m en t. In th e absen ce of hydroceph alus, DW M m ay be follow ed. W h en t reatm en t is n ecessary, th e posterior fossa cyst m ust be sh un ted. Sh un tin g th e lateral ven tricles alon e is con train dicated because of th e risk of upw ard h ern iation .35 How ever, it is im portan t to con firm paten cy of th e cerebral aque- duct , oth erw ise th e supraten torial ven tricles n eed to be sh un ted con com itan tly. Var yin g reports exist regardin g rates of associated aqueductal sten osis, alth ough it is w idely believed to be rare. An oth er option on ce used com m on ly is excision of th e obstruct ing m em bran e. Th is h as fallen out of favor due to its associated risks of m orbidit y an d m ortalit y. How ever, it rem ain s an opt ion for patien ts w ith frequen t sh un t m alfun ction s. New er treatm ents in clude endoscopic third ventriculostom y in cases w here the aqueduct is pat- en t, h ow ever fu r th er st u d y is n ecessar y.36,37 15.3.7 Prognosis Progn osis ran ges w idely as th ere are various levels of severit y of th e m alform at ion . Som e pediatric neurosurgical literature quotes 12–50% m ortalit y rates, although this is im proving w ith m odern sh un tin g tech n iques. On ly 50% h ave n orm al IQ. Ataxia, spasticit y, an d poor fin e m otor con trol are com m on . Seizures occur in 15%.

258 Developm ental Anom alies 15.4 Aqueduct al st enosis 15.4.1 General inform at ion Aqueductal sten osis (AqS) produces w h at is som etim es called t riven tricular hydroceph alus, ch arac- terized by a n orm al sized 4th ven tricle an d en larged th ird an d lateral ven tricles on MRI or CT. Most cases occur in ch ildren , h ow ever som e presen t for th e first tim e in adulth ood. 15.4.2 Et iologies 1. a congen ital m alform ation : m ay be associated w ith Ch iari m alform at ion or n eurofibrom atosis 2. acquired a) due to in flam m ation (follow in g h em orrh age or in fect ion , e.g. syph ilis, T.B.) b) n eoplasm : especially brain stem astrocytom as – in cludin g tectal gliom as (p. 634), lipom as c) quadrigem inal plate arachnoid cysts 15.4.3 Aqueduct al st enosis in infancy AqS is a frequen t cause of congen ital hydroceph alus (HCP) (up to 70% of cases27), but occasionally m ay be th e result of HCP. Pat ien ts w ith congen ital AqS usually h ave HCP at birth or develop it w ith in ≈ 2–3 m os. Congen ital AqS m ay be due to an X-lin ked recessive gene.28 Four t ypes of congen ital AqS described by Russell (sum m arized38): 1. forkin g: m ultiple ch an n els (often n arrowed) w ith n orm al epith elial lin in g th at do n ot m eet, sepa- rated by n orm al n er vous t issue. Usually associated w ith oth er congen ital abn orm alities (spin a bifida, m yelom en ingocele) 2. periaqueductal gliosis: lum in al narrow in g due to subepen dym al ast rocyt ic proliferation 3. true sten osis: aqueduct h istologically n orm al 4. septum 15.4.4 Aqueduct al st enosis in adult hood General inform at ion AqS m ay be an overlooked cause of “n orm al pressure hydroceph alus” in th e adult .39 It is un kn ow n w hy som e cases of AqS w ould rem ain occult, an d m an ifest on ly in adulth ood. In one series of 55 cases,40 35%h ad duration of sym ptom s < 1 year, 47%for 1–5 years; th e lon gest w as 40 yrs. Alth ough m ost follow th is lon gstan ding ben ign course, th ere are reports of elevated ICP an d sudden death . Sym pt om s See Table 15.5. Headach e w as th e m ost com m on sym ptom , an d h ad ch aracteristics of H/A associ- 1 5 ated w ith elevated ICP. Visual ch anges w ere n ext, an d usually con sisted of blurring or loss of acuit y. En docrin e ch anges in cluded m en st rual irregularit ies, hypothyroidism , an d h irsutism . Sig n s Papilledem a w as th e m ost com m on fin din g (53%). Visual fields w ere n orm al in 78%, th e rem ain der h aving reduced periph eral vision , in creased blin d spots, quadran tic or h em ian opic field cuts, or sco- tom ata. In tellectual im pairm en t w as presen t in at least 36%. Oth er sign s in cluded: ataxia (29%), “pyr- am idal t ract sign s” in 44% (m ild h em i- or para-paresis (22%), spasticit y (22%), or Babin ski’s (20%)), an osm ia (9%). Evaluat ion MRI is th e test of ch oice. MRI w ill sh ow th e absen ce of th e n orm al flow void in th e Sylvian aqueduct . Con trast sh ould be given to rule-out t um or. Treat m ent (of non-t um oral AqS) Alth ough treatm en ts of th e prim ar y lesion h ave been attem pted (e.g. lysis of aqueductal sept um ), th is h as fallen in to disfavor w ith th e im proved e cacy of CSF sh un ting an d en doscopic th ird ven tri- culostom y (ETV).

Prim ary Intracranial Anom alies 259 Table 15.5 Symptoms of aqueductal stenosis presenting in adulthood (55 patients > 16 years age40) Sym pt om No. % H/A 32 58% visual disturbances 22 40% m ental deterioration 17 31% gait disturbance 16 29% frequent falling 13 24% endocrine disturbance 10 18% nausea/vom iting 9 16% seizures 8 15% in co n t in e n ce 7 13% ve rt ig o 6 11% LE weakness 4 7% hem iparesis or hem ianesthesia 4 7% diplopia 3 5% d ysa rt h ria 1 deafness 1 1. sh un tin g: CSF is usually sh un ted to th e periton eum or th e vascular system , h ow ever sh un tin g to subarach noid space is also feasible (on ce obstruct ion at th e level of th e arachn oid gran ulation s has been ruled out) 2. a Torkildsen sh un t (sh un tin g a lateral ven tricle to th e cistern a m agn a41) m ay w ork in adult cases,38 h ow ever pediatric pat ien ts w ith obstructive hydroceph alus m ay n ot h ave an adequately developed subarachn oid space for th is to fun ct ion properly 3. endoscopic third ventriculostomy (p. 415) Follow -up of at least t w o years to rule out t um or is recom m en ded. 15 15.5 Agenesis of t he corpus callosum 15.5.1 General inform at ion A failure of com m issurat ion occurrin g ≈ 2 w eeks after con ception . Results in expan sion of th e th ird ven tr icle an d separat ion of th e lateral ven tr icles (w h ich develop dilated occipital h orn s an d atria, an d con cave m edial borders). Th e corpus callosum (CC) form s from rostr um (gen u) to splen ium ,42 in agen esis th ere m ay be an an terior portion w ith absen ce of th e posterior segm en t (th e converse occurs in frequen tly). Absen ce of th e an terior CC w ith presen ce of som e posterior CC is in dicative of som e form of h oloprosen ceph aly. 15.5.2 Incidence 1 in 2,000–3,000 n euroradiological exam in ation s. 15.5.3 Associat ed neuropat hologic findings See referen ce.43 ● porenceph aly

260 Developm ental Anom alies ● m icrogyria ● in terh em isph eric lipoma s an d lipom as of th e corpus callosum (p. 260) ● arh in en ceph aly ● optic atrophy ● colobom as ● hypoplasia of th e lim bic system ● bun dles of Probst: abor ted begin n ings of corpus callosum , bulge in to lateral ven t ricles ● loss of horizontal orientation of cin gulate gyrus ● sch izen ceph aly (p. 288) ● an terior an d h ippocam pal com m issures m ay be totally or part ially absen t44 ● hydrocephalus ● cysts in the region of the corpus callosum ● spina bifida w ith or w ith out m yelom en ingocele ● absence of th e septum pellucidum (p.260) 15.5.4 Possible present at ion ● hydrocephalus ● m icrocephaly ● seizures (rare) ● precocious puberty ● discon n ect ion syn drom e: m ore likely w ith a cquired CC defect th an in congen ital May be an in ciden tal fin din g, an d by itself m ay h ave n o clin ical sign ifican ce. How ever, m ay be occur as part of a m ore com plex clin ical syn drom e or ch rom osom al abn orm alit y (e.g. Aicardi syn drom e: agen esis of CC, seizures, retardation , patch es of retin al pigm en tation ). 15.6 Absence of t he sept um pellucidum Etiologies45 (p 178) 1. holoprosencephaly (p.289) 2. sch izen ceph aly (p. 288) 3. agen esis of th e corpus callosum (p. 259) 4. Ch iari t ype 2 m alform at ion (p. 284) 5. basal encephalocele 6. porenceph aly/hydranen cephaly 7. m ay occur in severe hydrocephalus: thought to be due to n ecrosis w ith resorption of the septum 8. septo-optic dysplasia: see below 1 5 Sep to-opt ic d ysp lasia46,45 (p 175–8) AKA de Morsier syn drom e. In com plete early m orph ogen esis of an terior m idlin e struct ures produ- ces hypoplasia of th e opt ic n er ves an d possibly optic ch iasm (a ected patien ts are blin d) an d pitui- tar y in fun dibulum . Th e sept um pellucidum is absen t in about h alf th e cases. About h alf th e cases also have schizen ceph aly (p.288). Pr esen t at ion m ay b e d u e t o se con d ar y h yp op it u it ar ism m a n ife st in g as d w a r fism , isolat e d grow t h h orm on e d eficien cy, or p an hyp op it u it ar ism . Occasion ally hyp ersecret ion of grow t h horm one, corticot ropin or prolactin m ay occur, an d precocious pubert y m ay occur. Most p at ie n t s ar e of n or m al in t ellige n ce alt h ou gh r et ard at ion m ay occu r. Se p t o - op t ic d ysp lasia m ay b e a le ss seve r e for m of h olop rose n ce p h aly (p . 28 9 ), an d occasion ally m ay occu r as p ar t of t h is an om aly (w it h it s at t e n d an t p oor e r p r ogn osis for fu n ct ion or su r vival ). Th e ve n t r icles m ay b e norm al or dilated. May be seen by the neurosurgeon because of concerns of possible h yd r o ce p h a lu s. 15.7 Int racranial lipom as 15.7.1 General inform at ion In tracran ial an d in traspin al lip om as are felt to be of m ald evelopm en tal origin 47 (p 706) an d m ay arise from failure of involution of th e prim itive m en in ges.48

Prim ary Intracranial Anom alies 261 15.7.2 Epidem iology of int racranial lipom as In ciden ce: 8 in 10,000 autopsies. Usually foun d in or n ear th e m idsagit tal plan e, particularly over th e corpus callosum ; lipom as in th is region are frequen tly associated w ith agen esis of th e corpus callos- um (p. 259). Th e tuber cin ereum an d quadrigem in al plate are less frequen tly a ected.43 Rarely, th e CP an gle or cerebellar verm is m ay be involved. May occur in isolat ion , but also h as been described in association w ith a n um ber of congen ital an om alies, in cluding: trisom y 21, Pai’s syn drom e, fron tal en ceph alocele, facial an om alies…. Oth er m idlin e abn orm alit ies m ay also be foun d: agen esis of th e corpus callosum , m yelom en ingocele, an d spin a bifida.48 15.7.3 Evaluat ion May be diagn osed by CT, MRI (study of ch oice), an d by ult rasoun d in in fan ts. CT: Low den sit y, m ay h ave periph eral calcification (di cult to appreciate on MRI).48 Di eren tial diagn osis on CT: prim arily bet w een derm oid cyst, teratom a49 an d germ in om a.48 MRI: ch aracteristic fin din g is a m idlin e lesion w ith sign al ch aracteristics of fat (h igh in ten sit y on T1WI, low in tensit y on T2W I). 15.7.4 Present at ion Often discovered in ciden tally. Large lipom as m ay be associated w ith seizures, hypothalam ic dysfun c- t ion , or hydroceph alus (possibly from com pression of th e aqueduct). Associated fin din gs th at m ay or m ay n ot be directly related: m en tal retardation, behavioral disorders and h eadache. 15.7.5 Treat m ent Direct surgical approach is seldom n ecessar y for in t racran ial lipom as.49 Sh un tin g m ay be required for cases w h ere hydroceph alus results from obstruction of CSF circulat ion .49 15.8 Hypot halam ic ham art om as 15.8.1 General inform at ion Key concept s 15 ● rare, non-neoplastic congenital malformation, usually occurs in tuber cinereum ● m ay be parahypothalamic (pedunculated) or intrahypothalamic (sessile) ● presentation: precocious pubert y, seizures (usually starting with gelastic seizures (brief unprovoked laughter)), developmental delay ● treatment: GnRH analogs for precocious pubert y. Latero-basal craniotomy for pedunculated lesions, transcallosal interforniceal approach for intrahypothalam ic lesions, option of endoscopic approach for lesions ≤ 1.5 cm dia, stereotactic radiosurgery may be an alternative Hypoth alam ic h am artom as (HH; h am artom a: an abn orm al conglom erat ion of cells n orm ally foun d in the sam e area) AKA dien ceph alic h am artom as or h am ar tom as of th e t uber cin ereum . Rare, n on - n eoplastic congen ital m alform at ion s arisin g from in ferior hypoth alam us or t uber cin ereum (floor of th e third ven tricle bet w een th e in fun dibular stalk an d th e m am m illary bodies). May occur as part of Pallister-Hall syn drom e (gen et ics: AD in h erited defect in GL13 gene resultin g in abn orm ally sh ort GL13 protein w h ich participates in n orm al sh apin g of m any organ s). 15.8.2 Clinical findings 1. specific t ypes of seizures: a) gelastic seizures (brief episodes of unprovoked laugh ter50) are the m ost characteristic t ype an d are th e earliest seizure m an ifestation . Presen t in up to 92%of patien ts.51 Th ey are resist- an t to m edical m an agem en t an d can lead to cogn itive an d beh avioral deficits.52 Not path o- gn om on ic. A n eocort ical origin h as been described 53

262 Developm ental Anom alies b) epileptic en ceph alopathy: gelastic fits gradually in crease in frequen cy an d oth er seizure t ypes accrue: com plex part ial seizures, drop attacks, ton ic seizures, ton ic-clon ic seizures, an d secon - darily gen eralized seizures. Th is ph ase is associated w ith m arked deterioration of cogn itive an d behavioral abilities. Develops in 52%by a m ean age of 7 years51 2. precocious pubert y: believed to be due to release of gonadotropin -releasing h orm on e (Gn RH) foun d w ith in h am artom a cells.54 HH are th e m ost com m on CNS t um or to cause precocious pub- ert y, oth er causes in clude: oth er CNS t um ors – astrocytom a, epen dym om a, pin eal t um ors (p.658), optic/hypoth alam ic gliom as (especially in NFT patien ts) -, CNS XRT, hydroceph alus, CNS in flam m ation , septo-optic dysplasia (p. 260), an d ch ron ic hypothyroidism 3. developm en tal delay: prim arily in patien ts w ith seizure disorder (severit y correlates w ith dura- tion of seizures). 46%of patien ts have borderlin e in tellectual fun ct ion (m en tal retardation ) 4. beh avioral disturban ces55: aggressive beh avior, rage attacks… 15.8.3 Im aging MRI: n on en h an cin g, isoin ten se on T1W I, sligh tly hyperin tense or isoin ten se on T2W I.56 15.8.4 Pat hology Tw o su bt yp es of hyp oth alam ic h am artom as56,51: 1. pedun culated or parahypoth alam ic: n arrow er base attach ed to th e floor of th e hypoth alam us (n ot arisin g w ith in hypoth alam us). No distort ion of 3rd ven tr icle. Gen erally associated w ith pre- cocious pubert y m ore than seizures 2. intrathalam ic or sessile: w ithin hypothalam us (distorting the 3rd ventricle) or broad attachm en t to hypoth alam us. More often associated w ith seizures. 66%h ave developm en tal delay, 50%h ave precocious pubert y Microscop ic p at h ology: Clusters of disorgan ized sm all n euron s surroun ded by large pyram idal like n euron s in an astrocyte-rich n europil57 (in con trast to th e usual gan glion cells surroun ded by oligo- den drocytes foun d in th e hypothalam us). 15.8.5 Treat m ent Precocious pubert y usually respon ds w ell to Gn RH an alogs.58 In d icat ion s for su rger y: 1. precocious pubert y th at fails to respon d to m edical th erapy (Gn RH an alogs) 2. seizures th at can n ot be adequately con trolled m edically. Post-op seizure con trol is related to com pleteness of resection 3. n eurologic deficit from m ass e ect of th e t um or 15 Op t ion s: 1. surgical resection a) pedun culated lesion s: approach es in clude59 subtem poral, subfron tal, pterion al, orbitozygo- m at ic (m ost com m on ly recom m en ded). Risks: cran ial n europath y, st roke59 b) sessile lesion s w ith in t raven tr icular com pon en t: t ran scallosal an terior in terforn iceal approach .60,61,62 Risks: m em or y im pairm en t (forn iceal injur y), en d ocrin e distu rban ces, w eigh t gain 60,62 c) n euroen doscopic approach : con sidered for HH ≤ 1.5 cm diam eter.63 Risks: 25%in ciden ce of thalam ic cerebrovascular injur y 2. stereotactic radiosurger y: especially for sm all sessile lesion s, subtotal resection , or patien ts refus- in g or n ot can didates for surgery. In sm all series, 3-year outcom e sh ow ed im provem en t sim ilar to surgical resection w ith less n eurologic an d en docrin ologic m orbidit y64,65 Re fe r e n ce s Report of 23 Con secu tive Cases of th e So-called Tem p oral Lobe Agen esis Syn drom e. Neuroch irugia. [1] Van Der Mech e F, Braakm an R. Arach n oid Cysts in th e Middle Cran ial Fossa: Cause an d Treatm ent of 1982; 25:51–56 Progressive an d Non -Progressive Sym ptom s. J Neu- [3] Ren gach ary SS, Watan abe I. Ultrastruct u re an d rol Neu rosu rg Psych iatr y. 1983; 46:1102–1107 Pathogen esis of In tracran ial Arach noid Cysts. J Neu- [2] Mayr U, Aich n er F, Bau er G, et al. Su praten torial rop ath ol Exp Neurol. 1981; 40:61–83 Ext racerebral Cysts of th e Middle Cran ial Fossa: A

Prim ary Intracranial Anom alies 263 [4] Harsh GR, Edw ards MSB, W ilson CB. In tracran ial [28] Matson DD. Neu rosu rgery of In fan cy an d Ch ild- 15 Arach noid Cysts in Ch ildren . J Neurosurg. 1986; h ood. 2n d ed. Sprin gfield: Ch arles C Th om as; 1969 64:835–842 [29] Suw an wela C, Su w anw ela N. A Morp h ological Clas- [5] Pierre-Kah n A, Cap elle L, Brau n er R, Sain te-Rose C, sification of Sin cipital En ceph alom en ingoceles. J et al. Presentation and Man agem en t of Suprasellar Neurosurg. 1972; 36:201–211 Arach noid Cysts: Review of 20 Cases. J Neurosurg. 1990; 73:355–359 [30] In cesu L, Kh osia A. Dan dy-Walker m alform ation . 2008 [6] Altsch u ler EM, Jun greis CA, Sekh ar LN, Jan n etta PJ, et al. Operative Treatm en t of In tracran ial Epider- [31] Calabro F, Arcuri T, Jin kin s JR. Blake's pouch cyst: an m oid Cysts an d Ch olesterol Gran ulom as: Report of en t it y w ithin the Dandy-Walker con tin uum . Neuro- 21 Cases. Neurosurgery. 1990; 26:606–614 radiology. 2000; 42:290–295 [7] Galassi E, Togn etti F, Gaist G, et al. CT scan an d Met- [32] Forzano F, Man sour S, Ierullo A, Hom fray T, Th ilaga- rizam ide CT Cistern ograph y in Arach n oid Cysts of n ath an B. Posterior fossa m alform ation in fetuses: a th e Middle Cran ial Fossa. Surg Neurol. 1982; 17:363–369 rep ort of 56 fur th er cases an d a review of th e litera- t ure. Prenat Diagn. 2007; 27:495–501 [8] Hop f NJ, Pern eczky A. En doscop ic Neu rosu rger y [33] Hirsch JF, Pierre-Kahn A, Renier D, et al. Th e Dan dy- an d En doscope-Assisted Micron eurosurgery for th e Walker Malform ation : A Review of 40 Cases. J Neu- Treatm ent of In tracranial Cysts. Neurosurger y. rosurg. 1984; 61:515–522 1998; 43:1330–1337 [34] Raim ondi AJ, Sam uelson G, Yarzagaray L, et al. Atre- sia of th e Foram in a of Lu sch ka an d Magendie: Th e [9] Page LK. Com m en t on Albrigh t L: Treatm en t of Bob - Dan dy-Walker Cyst. J Neu rosu rg. 1969; 31:202–216 ble-Head Doll Syn drom e by Tran scallosal Cystec- [35] Moh an t y A, Bisw as A, Satish S, Prah araj SS, Sast ry KV. Treatm en t option s for Dan dy-Walker m alform a- tom y. Neurosurger y. 1981; 8 tion. J Neurosurg. 2006; 105:348–356 [10] Albrigh t L. Treatm en t of Bobble-Head Doll Syn d ro- [36] Garg A, Suri A, Chan dra PS, Kum ar R, Sh arm a BS, Mah apatra AK. En d oscopic th ird ven triculostom y: 5 m e by Tran scallosal Cystectomy. Neurosurgery. 1981; 8:593–595 years' exp erien ce at th e All In d ia In stit u te of Medi- [11] Golabi M, Ed ward s MSB, Ousterh ou t DK. Cran iosy- cal Scien ces. Ped iatr Neu rosu rg. 2009; 45:1–5 nostosis an d Hydrocep h alu s. Neurosurgery. 1987; [37] Sikorski CW , Curr y DJ. En d oscop ic, sin gle-cath eter 21:63–67 treatm en t of Dan d y-Walker syn drom e hydrocep h a- [12] Ren ier D, Sain te-Rose C, March ac D, Hirsch J-F. lus: techn ical case report and review of treatm ent Intracran ial Pressure in Cran iostenosis. J Neurosurg. option s. Pediatr Neurosurg. 2005; 41:264–268 1982; 57:370–377 [38] Nag TK, Falcon er MA. Non -Tu m oral Sten osis of th e [13] Bu rke MJ, W in ston KR, W illiam s S. Norm al Su t ural Aqued u ct in Adu lts. Brit Med J. 1966; 2:1168–1170 [39] Van n este J, Hym an R. Non -Tu m oral Aqu edu ct Fusion and th e Etiology of Single Sut ure Craniosy- Sten osis an d Norm al Pressure Hydroceph alus in th e n ostosis: Th e Microspicule Hypoth esis. Pediatr Neu- Elderly. J Neurol Neurosurg Psych iat r y. 1986; rosurg. 1995; 22:241–246 49:529–535 [14] Tuite GF, Evan son J, Ch on g W K, et al. Th e Beaten Copp er Cran iu m : A Correlation bet w een In tracran i- [40] Harrison MJG, Robert CM, Ut tley D. Ben ign Aqu e- al Pressure, Cran ial Radiograp h s, an d Com p u ted du ct Sten osis in Adu lts. J Neurol Neu rosu rg Psych ia- Tom ograph ic Scan s in Ch ildren w ith Cran iosyn osto- tr y. 1974; 37:1322–1328 sis. Neu rosu rgery. 1996; 39:691–699 [15] Ch ad du ck W M, Ch ad du ck JB, Boop FA. Th e Subar- [41] Alp MS. W h at is a Torkildsen sh u n t? Su rg Neurol. ach n oid Sp aces in Cran iosyn ostosis. Neu rosu rgery. 1995; 43:405–406 1992; 30:867–871 [16] Gates GF, Dore EK. Detection of Cran iosyn ostosis by [42] David son HD, Abrah am R, Stein er RE. Agen esis of th e Corp us Callosum : Magn et ic Reson an ce Im agin g. Bon e Scan n in g. Radiology. 1975; 115:665–671 Radiology. 1985; 155:371–373 [17] Wall SA, Th om as GP, Joh n son D, Byren JC, Jayam o- [43] Atlas SW , Zim m erm an RA, Bilan iu k LT, et al. Corp u s h an J, Magdum SA, McAuley DJ, Rich ards PG. Th e Callosu m an d Lim bic System : Neuroan atom ic MR preoperative in ciden ce of raised in tracranial pres- Evaluation of Developm en tal Anom alies. Radiology. sure in n on syn drom ic sagittal craniosyn ostosis is underestim ated in the literature. J Neurosurg 1986; 160:355–362 Pediatr. 2014; 14:674–681 [44] Loeser JD, Alvord EC. Agen esis of th e Corp us Callos- [18] Ren ier D, Arn aud E, Cinalli G, et al. Progn osis for Men tal Fu n ct ion in Ap ert's Sydrom e. J Neu rosu rg. u m . Brain . 1968; 91:553–570 1996; 85:66–72 [45] Taveras JM, Pile-Spellm an J. Neurorad iology. 3rd [19] Muakkassa KF, Ho m an HJ, Hin ton DR, Hen drick ed. Balt im ore: W illiam s an d W ilkins; 1996 EB, et al. Lam bdoid Syn ostosis: Part 2: Review of [46] Jon es KL. Sm ith 's Recogn izable Pattern s of Hum an Cases Man aged at Th e Hosp ital for Sick Ch ild ren , 1972-1982. J Neurosurg. 1984; 61:340–347 Malform ation . 4th ed. Ph ilad elp h ia: W .B. Saun d ers; [20] Keatin g RF, Goodrich JT. Lam bdoid Plagioceph aly. 1988 Con tem p Neurosurg. 1996; 18:1–7 [47] Ru ssell DS, Ruben stein LJ. Pathology of Tum ou rs of [21] Morrison DL, MacEw en GD. Congen ital Muscular th e Nervous System . 5th ed. Balt im ore: W illiam s Torticollis: Observat ion s Regardin g Clin ical Fin d- an d Wilkin s; 1989 in gs, Associated Con dition s, an d Resu lts of Treat- [48] Rubio G, Garcci Guijo C, Mallada JJ. MR an d CT Diag- m en t. J Pediatr Or th op. 1982; 2:500–505 [22] Am erican Academ y of Pediatrics Task Force on n osis of In tracran ial Lipom a. AJR. 1991; 157:887– In fan t Positionin g and SIDS. Posit ion in g and SIDS. 888 [49] Kazner E, Stoch dorph O, Wen de S, Grum m e T. In tra- Pediatrics. 1992; 89:1120–1126 cran ial Lipom a. Diagn ost ic an d Th erapeut ic Con sid- [23] Higgin bottom MC, Jon es KL, Jam es HE. In trau terin e erations. J Neurosurg. 1980; 52:234–245 [50] Daly D, Mulder D. Gelast ic epilepsy. Neurology. Con st rain t an d Cran iosyn ostosis. Neu rosu rgery. 1957; 7:189–192 1980; 6 [51] Nguyen D, Singh S, Zaatreh M, Novot ny E, Levy S, [24] Hin ton DR, Becker LE, Muakkassa KF, Ho m an HJ, Testa F, Spen cer SS. Hypoth alam ic h am ar tom as: et al. Lam bdoid Syn ostosis: Part 1: Th e Lam bdoid seven cases an d review of th e literat ure. Ep ilep sy Sut ure: Norm al Developm en t an d Pathology of Behav. 2003; 4:246–258 'Syn ostosis'. J Neurosurg. 1984; 61:333–339 [25] McCom b JG. Treatm en t of Fun ct ional Lam bdoid [52] Strian o S, Meo R, Bilo L, Cirillo S, Nocerin o C, Ruosi Syn ostosis. Neurosurg Clin North Am . 1991; 2 P, Strian o P, Estran eo A. Gelast ic ep ilep sy: sym p to- [26] Clarren SK. Plagioceph aly an d Tor ticollis: Etiology, m atic an d cr yptogen ic cases. Epilepsia. 1999; Natural Histor y, an d Helm et Treatm en t . J Pediatr. 40:294–302 1981; 98 [53] Kurle PJ, Sh eth RD. Gelast ic seizures of neocort ical [27] Sect ion of Pediatric Neurosurgery of th e Am erican origin con firm ed by resective su rger y. J Ch ild Neu- rol. 2000; 15:835–838 Association of Neu rological Surgeon s. Ped iatric Neu rosu rger y. New York 1982 [54] Culler FL, Jam es HE, Sim on ML, Jones KL. Identifica- tion of gonadotropin-releasing horm one in neurons of a hypothalam ic ham artom a in a boy w ith preco- cious pu bert y. Neu rosu rger y. 1985; 17:408–412

264 Developm ental Anom alies [55] Prigatan o GP. Cogn it ive an d behavioral d ysfu n ct ion w ith gelastic epilepsy. Neurosurger y. 2001; in ch ildren w ith h ypoth alam ic h am artom a and epi- 48:108–118 lepsy. Sem in Pediatr Neurol. 2007; 14:65–72 [61] Ng Y, Rekate HL, Kerrigan JF, et al. Tran scallosal resection of a hyp oth alam ic h am artom a: Case [56] Arita K, Ikawa F, Ku risu K, Sum ida M, Harad a K, rep or t . BNI Quar terly. 2004; 20:13–17 Uozum i T, Monden S, Yosh ida J, Nish i Y. Th e rela- tion sh ip betw een m agn etic reson ance im agin g [62] Ng YT, Rekate HL, Pren ger EC, Ch u n g SS, Feiz-Erfan fin din gs an d clin ical m an ifestation s of h ypoth ala- I, Wan g NC, Varlan d MR, Kerrigan JF. Tran scallosal resection of hypoth alam ic h am artom a for in tract- m ic ham artom a. J Neurosurg. 1999; 91:212–220 able ep ilep sy. Epilepsia. 2006; 47:1192–1202 [57] Coon s SW, Rekate HL, Pren ger EC, Wan g N, Drees C, [63] Rekate HL, Feiz-Erfan I, Ng YT, Gon zalez LF, Kerrigan Ng YT, Ch u n g SS, Kerrigan JF. Th e h istop ath ology of JF. Endoscopic surgery for hypothalam ic h am ar to- hypothalam ic h am artom as: study of 57 cases. J m as causing m edically refractory gelast ic epilepsy. Neuropathol Exp Neu rol. 2007; 66:131–141 Ch ilds Nerv Syst. 2006; 22:874–880 [58] Ch am ou illi JM, Razafim ah efa B, Pierron H. [Preco- cious puberty and hypothalam ic ham artom a: treat- [64] Regis J, Scavard a D, Tam u ra M, Villen eu ve N, Barto- m en t w ith t rip torelin d urin g eigh t years]. Arch lom ei F, Bru e T, Moran ge I, Dafon seca D, Ch au vel P. Pediatr. 1995; 2:438–441 Gam m a kn ife su rgery for ep ilep sy related to hyp o- [59] Feiz-Erfan I, Horn EM, Rekate HL, Spetzler RF, Ng YT, Rosen feld JV, Kerrigan JF,3rd . Surgical strategies th alam ic h am artom as. Sem in Pediatr Neurol. 2007; for approach ing hypothalam ic h am artom as causin g 14:73–79 gelastic seizures in th e pediatric population : trans- [65] Math ieu D, Kon d ziolka D, Niran jan A, Flickin ger J, ventricular com pared w ith skull base approach es. J Lun sford LD. Gam m a kn ife radiosurger y for refrac- tory epilepsy caused by hypothalam ic ham artom as. Neurosurg. 2005; 103:325–332 Stereotact Fun ct Neurosurg. 2006; 84:82–87 [60] Rosen feld JV, Harvey AS, Wren n all J, Zach arin M, Berkovic SF. Tran scallosal resection of hyp oth alam ic h am artom as, w ith con trol of seizures, in ch ildren 15

Prim ary Spinal Anom alies 265 16 Prim ary Spinal Anom alies 16.1 Spinal arachnoid cyst s 16.1.1 General inform at ion Alm ost always dorsal, m ost com m on in th oracic spin e. W ith a ven tral cyst, con sider a n euren teric cyst (see below ). Most are act ually extradural an d th ese are som etim es referred to as arach n oid divert icula – th ese m ay be associated w ith kyph oscoliosis in juven iles or w ith spin al dysraph ism . In tradural arach n oid cysts m ay be congen ital or m ay follow in fect ion or traum a. Usually asym ptom atic, even if large. 16.1.2 Treat m ent W h en in dicated, treat m en t option s in clude: 1. percutan eous procedures: m ay be don e un der MRI1 or CT guidan ce. CT guidan ce usually requires use of in trath ecal contrast to delin eate the cyst a) needle aspiration b) n eedle fen estration1 2. open surgical resection or fen estration 16.2 Spinal dysraphism (spina bifida) 16.2.1 Definit ions See referen ce.2 Sp in a bifid a occu lt a. Congen ital absen ce of a spin ous process an d variable am oun ts of lam in a. No visible exposure of m en inges or n eural tissue. Th e follow in g t w o en tit ies are grouped togeth er un der th e term spina bifida apert a (aperta from th e Latin for “open”) or spin a bifida cystica. Men in gocele. Congen ital defect in ver tebral arch es w ith cystic disten sion of m en in ges, but n o abn orm alit y of n eural tissue. On e th ird h ave som e n eurologic deficit . Myelom en in gocele. Con gen ital defect in vertebral arch es w ith cystic dilatat ion of m en in ges an d st ruct ural or fun ct ion al abn orm alit y of spin al cord or cauda equin a. 16.2.2 Spina bifida occult a (SBO) 16 Reported prevalen ce ran ge of SBO: 5–30% of North Am erican s (5–10% is probably m ore realistic). Th e defect m ay be palpable, an d th ere m ay be overlyin g cutan eous m an ifestat ion s (in Table 16.3. Often an in ciden tal fin din g, usually of n o clin ical im por tan ce when it occurs a lone. Num erous review s h ave sh ow n n o statistical association of SBO w ith n on specific LBP.3,4 An in creased in ciden ce of disc h ern iation w as sh ow n in on e st udy.5 SBO m ay occasion ally be associated w ith diastem atomyelia, teth ered cord, lipom a, or derm oid t um or. W h en sym ptom at ic from on e of th ese associated con dition s, th e presen tation is usually th at of teth ered cord; gait disturban ce, leg w eakn ess an d atrophy, urin ar y dist urban ce, foot deform - ities…, see Teth ered cord syn drom e (p. 272). 16.2.3 Myelom eningocele Em bryology Th e an terior n europore closes at gestation day 25. Th e caudal n europore closes at day 28. Epidem iology/genet ics In ciden ce of spin a bifida w ith m en in gocele or m yelom en ingocele (MM) is 1–2/1000 live birth s (0.1– 0.2%). Risk in creases to 2–3% if th ere is on e previous birth w ith MM, an d 6–8% after t w o a ected ch ildren . Th e risk is also in creased in fam ilies w h ere close relatives (e.g. siblin gs) h ave given bir th to

266 Developm ental Anom alies MM ch ildren , especially w h en on th e m oth er’s side of th e fam ily. In ciden ce m ay in crease in tim es of w ar, fam in e or econ om ic disasters, but it m ay be gradually declin ing overall.6 Tran sm ission follow s n on -Men delian gen etics, an d is probably m ultifactorial. Pren atal folate (in th e form of folic acid) low - ers the incidence of MM (p.290). Hydrocephalus in m yelom eningocele Hydroceph alus (HCP) develops in 65–85%of patien ts w ith MM, an d 5–10%of MM patien ts h ave clin - ically overt HCP at bir th .7 Over 80% of MM pat ien ts w h o w ill develop HCP do so before age 6 m os. Most MM patien ts w ill h ave an associated Ch iari t ype 2 m alform at ion (p. 284). Closure of th e MM defect m ay convert a laten t HCP to act ive HCP by elim in atin g a route of egress of CSF. Latex allergy in m yelom eningocele Up to 73%of MM patien ts are allergic to protein s present in latex (th e m ilky sap from th e rubber t ree Hevea brasilien sis), foun d on ly in n aturally occurring rubber products (an d w h ich are n ot presen t in syn th etics such as: silicon e, vinyl, plastic, n eopren e, n itrile…). Th e allergy is th ough t to arise from early an d frequen t exposure to latex products durin g m edical care for th ese patien ts, an d th ere is a suggestion th at latex-free surgery on th ese in fan ts m ay reduce th e risk of th e developm en t of latex a lle r g y.8 Prenat al diagnosis See Pren atal detect ion of n eural t ube defect s (p.290). Intrauterine closure of MM defect Con troversial. Does reduce in ciden ce of Ch iari II defect , but it h as n ot been determ in ed if th is is clin - ically sign ifican t. Argued w h eth er th is reduces in ciden ce of hydroceph alus. Does n ot im prove distal n eurologic fun ct ion . General m anagem ent Assessm ent and m anagem ent of lesion ● m easure size of defect ● assess w h eth er lesion is ruptured or un ruptured ○ ruptured: start an tibiotics (e.g. n afcillin an d gen tam icin ; D/C 6 h rs after MM closure, or con tin - ue if shunt an ticipated in next 5 or 6 days) ○ un ruptured: n o antibiotics n ecessary ● cover lesion w ith telfa, th en spon ges soaked in lact ated rin gers or n orm al salin e (form a sterile gauze rin g aroun d th e lesion if it is cystic an d protrudin g) to preven t desiccation ● Tren delen burg position , patien t on stom ach (keeps pressure o lesion ) ● perform surgical closure w ith in 36 h rs un less th ere is a con train dicat ion to surgery (sim ultan eous sh un t is n ot usually don e except if overt hydroceph alus (HCP) at birth ): see below 16 Neurological assessm ent and m anagem ent ● item s related to spin al lesion ○ w atch for spon taneous m ovem en t of th e LEs (good spontan eous m ovem en t correlates w ith bet- ter later fun ction al outcom e9) ○ assess low est level of n eurologic fun ct ion Table 16.1) by ch eckin g respon se of LEs to pain ful st im ulus: alth ough som e in fan ts w ill h ave a clear dem arcation betw een n orm al an d abn orm al levels, at least 50%sh ow som e m ixture of n orm al, reflex, an d auton om ous activity (arisin g from un in hibited anterior h orn m otor neurons)9 – di eren tiatin g reflex m ovem en t from volun tar y m ay be di cult. In gen eral, volun tar y m ove- m ent is not stereotyped w ith repetitive stim ulus and reflex m ovem ent usually only persists as long as the n oxious stim ulus is applied ● item s related to th e com m on ly associated Ch iari t ype 2 m alform at ion : ○ m easure OFC: risk of developin g hydroceph alus (see above). Use OFC graph s (p.395), an d also look for abn orm al rate of grow th (e.g. > 1 cm /day) ○ h ead U/S w ith in ≈ 24 h rs ○ ch eck for in spirator y st ridor, apn eic episodes

Prim ary Spinal Anom alies 267 Table 16.1 Findings in various levels of MM lesion10 Paralysis Findings b e lo w T12 com plete paralysis of all muscles in LEs L1 weak to m oderate hip flexion, palpable contraction in sartorius L2 strong hip flexion and m oderate hip adduction L3 normal hip adduction & alm ost norm al knee extension L4 normal hip adduction, knee extension & dorsiflexion/inversion of foot; some hip abduction in flexion L5 normal adduction, flexion &lateral rotation of hip; moderate abduction; normal knee extension, moderate flexion; normal foot dorsiflexion; hip extension absent; • produces dorsiflexed foot and flexed thigh S1 normal hip flexion & abduction/adduction, m oderate extension and lateral rotation; strong knee flexion & inversion/eversion of foot; m oderate plantarflexion of foot; extension of all toes, but flexion only of term inal phalanx of great toe; normal m edial & lateral hip rotation; com plete paralysis of foot intrinsic (except abductor and flexor hallicus brevis); • produces clawing of toes and flattening of sole of foot S2 difficult to detect abnorm alit y clinically; • with growth this produces clawing of the toes due to weakness of intrinsic muscles of sole of foot (innervated by S3) Ancillary assessm ent and m anagem ent ● evaluation by n eon atologist to assess for oth er abn orm alities, especially th ose th at m ay preclude surger y (e.g. pulm on ar y im m at urit y). Th ere is an average in ciden ce of 2–2.5 addit ion al an om alies in MM patients ● bladder: start patient on regular urinar y cath eterization s, obtain urological consultation (n on - em ergen t) ● AP & lat spin e film s: assess scoliosis (baselin e) ● orthopedic consultation for severe kyphotic or scoliotic spine deform ities and for hip or knee deform ities Surgical m anagem ent 16 Tim ing of MM closure Early closure of MM defect is not associated w ith im provem en t of n eurologic fun ction , but evidence supports low er in fect ion rate w ith early closure. MM sh ould be closed w ith in 24 h rs w h eth er or n ot m em bran e is in tact (after ≈ 36 h rs th e back lesion is colon ized an d th ere is in creased risk of postope- rative in fect ion ). Sim ultaneous MM defect closure and VP shunting In patien ts w ith out hydrocephalus, m ost surgeon s w ait at least ≈ 3 days after MM repair before sh un tin g. In MM patien ts w ith clin ically overt HCP at birth (ven triculom egaly w ith en larged OFC an d/or sym ptom s), MM repair an d sh un tin g m ay be perform ed in th e sam e sit ting w ith out in creased in ciden ce of in fect ion , an d w ith sh orter h ospitalization .11,12 It m ay also reduce th e risk of MM repair breakdow n previously seen durin g th e in ter val before sh untin g. Pat ien t is position ed pron e, h ead t urn ed to r ight (to expose th e righ t occiput), righ t kn ee an d th igh flexed to expose righ t flan k (con - sider usin g left flan k to preven t con fusion w ith appen dectom y scar later in life). Surgical technique of m yelom eningocele repair Key concept s ● critical goals: 1) free placode from dura (to avoid tethering), 2) water-tight dural closure, 3) skin clo- sure (can be accomplished in essentially all cases). Closure does not restore any neurologic function ● timing goal: surgical closure with latex-free setup ideally ≤ 36 hours after birth ● helpful tips: start at normal dura, open as wide as the defect, trim placode if necessary to close dura, undermine skin to achieve closure (avoid trapping skin → derm oid tumor) ● post-op CSF leak usually means a shunt is required

268 Developm ental Anom alies Gen eral prin ciples13: preven t desiccation – keep th e exposed n eural tissue m oist. Use latex-free environ m en t (reduces developm en t of latex allergy, as w ell as attack by m atern al an t ibodies th at m ay h ave crossed th rough th e placen ta). Do n ot allow scrub solution s or ch em ical an t im icrobials to con tact n eural placode. Do n ot use m on opolar cauter y. At ever y poin t durin g th e closure, avoid plac- ing ten sion on the n eural placode. Multiple layer closure is advocated, 5 layers should be attem pted, although occasionally on ly 2 or so layers m ay be closed. Th ere is n o evidence th at m ultiple layer closure eith er im proves n eurologic fun ct ion or preven ts later teth erin g, but th ere is a suggestion th at w h en teth erin g does occur, it m ay be easier to release w h en a previous m ultilayered closure w as perform ed. Silastic does n ot preven t adh eren ce in series w ith lon g follow -up (> 6 yrs), an d m ay even ren der un teth erin g procedures m ore di cult. Begin by dividing th e abn orm al epith elial coverin g from th e n orm al skin . Th e pia-arach n oid m ay be separated from the n eural t issue. Th e placode is folded in to a tube an d th e pia-arach n oid is th en approxim ated around it w ith 7–0 suture (absorbable suture, e.g. PDS, m ay m ake fut ure re-operat ion easier). It often h elps to start w ith n orm al dura above, an d th en w ork dow n . Th e dura can th en be isolated aroun d th e periph er y an d follow ed deep to th e spin al can al superiorly. Th e dura is th en also form ed in to a tube an d approxim ated in a w ater-t igh t closure. If th e dura can n ot be closed, th e pla- code m ay be judiciously trim m ed. Th e filum term in ale sh ould be divided if it can be located. Th e skin is th en m obilized an d closed. Derm oid t um ors m ay result from retain ed skin durin g th e closure, but altern atively derm oids m ay also be presen t congen itally.14 If th ere is a kyph otic deform it y, it is repaired at th e sam e sit tin g as th e MM defect closure. Th e kyph otic bon e is ron geured, an d 2–0 Vicr yl is used to suture th e adjacen t bon es. Som e surgeon s use a brace post-op, som e do not. Post-op m anagem ent of MM repair 1. keep patient o all incisions 2. bladder catheterization regim en 3. daily OFC m easurem en ts 4. a void na rcotics (m idbrain m alform ation ren ders th ese pat ien t m ore sen sitive to respirator y depression from n arcotics) 5. if not shunted a) regular h ead U/S (t w ice w eekly to w eekly) b) keep patien t flat to ↓ CSF pressure on in cision 6. if a kyph ectomy w as don e, use of a brace is option al (surgeon preferen ce) Lat e problem s/issues In clude: 1. hydrocephalus: m ay m im ic ≈ anyth in g listed below. ALWAYS RULE OUT SHUNT MALFUNCTION w hen a MM patient deteriorates 2. syrin gom yelia (an d/or syringobulbia) (p.1144): 3. Teth ered cord syn drom e (p. 272) as m any as 70%of MM pat ien ts h ave a teth ered cord radio- graph ically (som e quote 10–20%), but on ly a m in orit y are sym ptom atic. Un fort un ately th ere is n o 1 6 good test to ch eck for sym ptom atic retetherin g (SSEPs m ay deteriorate,15 m yelography m ay h elp) a) scoliosis: early un teth erin g of cord m ay im prove scoliosis; seeScoliosis in teth ered cord (p . 2 7 2 ) b) sym ptom at ic teth ering m ay m an ifest as delayed n eurological deterioration 16 4. derm oid tum or at th e MM site (p. 784) 17: in ciden ce ≈ 16% 5. m edullar y com pression at foram en m agn um , see sym ptom atic Ch iari II m alform at ion (p.284) 6. use of grow th h orm on e to in crease stature is con troversial Out com e W ith out any treatm en t, on ly 14–30% of MM in fan ts sur vive in fan cy; th ese usually represen t th e least severely involved; 70%w ill h ave n orm al IQ’s. 50%are am bulator y. W ith m odern t reatm en t, ≈ 85%of MM in fan ts sur vive. Th e m ost com m on cause of early m ortalit y are com plication s from th e Ch iari m alform ation (respirator y arrest, aspiration …), w h ere late m or tal- it y is usually due to sh un t m alfun ction . 80%w ill h ave n orm al IQ. Men tal retardation is m ost closely lin ked to sh un t in fect ion . 40–85%are am bulator y w ith bracing, h ow ever, m ost ch oose to use w h eel- ch airs for ease. 3–10% h ave n orm al urin ar y con tin en ce, but m ost m ay be able to rem ain dr y w ith interm ittent catheterization .

Prim ary Spinal Anom alies 269 16.2.4 Lipom yeloschisis General inform at ion Dorsal spinal dysraph ism w ith lipom a. Six form s are described,18 th e follow in g 3 are clin ically im por- tan t as possible causes of progressive n eurologic dysfun ct ion via teth erin g (p. 272) an d/or com pression: 1. (in t ra)dural lipom a 2. lipom yelom en ingocele (see below ) 3. fibrolipom a of th e filum term inale Lipom yelom eningocele General inform ation A subcutan eous lipom a th at passes th rough a m idlin e defect in th e lum bodorsal fascia, vertebral n eural arch , an d dura, an d m erges w ith an abn orm ally low teth ered cord.18 Th ese m ay be term in al, dorsal, or transitional (betw een the tw o). Th e in t radural fatt y t um or m ay also be kn ow n as lipom a of th e cauda equin a. In addition to being abn orm ally low, th e con us m edullaris is split in th e m idlin e dorsally usually at th e sam e level as th e bifid spin e, an d th is dorsal m yelosch isis m ay exten d superiorly un der in tact spin al arch es.19 Th ere is a thick fibrovascular band that joins th e lam ina of the m ost ceph alic vertebrae w ith the bifid lam ina. Th is ban d con stricts th e m en ingocele sac an d n eural tissue, causin g a kin k in th e superior surface of th e m en in gocele. Asym ptom at ic lipom as of th e filum term in ale occur in 0.2–4%20,21 of MRIs. Th e dura is deh iscen t at th e level of th e dorsal m yelosch isis, an d reflects on to th e placode. Th e lipom a passes th rough th is deh iscen ce to becom e attached to th e dorsal surface of th e placode, an d m ay con tin ue ceph alad un der in tact arch es w ith th e possibilit y of exten sion in to th e cen t ral can al superiorly to levels w ith out dorsal m yelosch isis. Th e lipom a is dist in ct from th e n orm al epidural fat w h ich is looser an d m ore areolar. Th e subarach noid space t ypically bulges to th e side con tralateral to th e lipom a. Th ese lipom as accoun t for 20%of covered lum bosacral m asses. Pre se n t a t io n In a pediatric series, 56%presen ted w ith a back m ass, 32%w ith bladder problem s, an d 10%because of foot deform ities, paralysis or leg pain .22 Physical exam ination Alm ost all patien ts h ave cutan eous stigm ata of th e associated spina bifida: fatt y subcutan eous pads (located over th e m idlin e an d usually exten ds asym m et rically to on e side) w ith or w ith out dim ples, port-w in e stain s, abn orm al h air, derm al sin us open in g, or skin appen dages.23 Clubbing of th e feet (talipes equinovarus) m ay occur. Th e n eurologic exam m ay be n orm al in up to 50% of patien ts (m ost presen tin g w ith skin lesion on ly). Th e m ost com m on n eurologic abn orm alit y w as sen sor y loss in th e sacral derm atom es. Evaluat ion 16 Plain LS spin e x-rays w ill sh ow spina bifida in m ost cases. Presen t in alm ost all by defin ition , but som e m ay h ave segm en tat ion an om alies in stead such as but terfly vertebra (p. 216). Abn orm alities of fusion an d sacral defect s m ay also be seen . Th e abn orm ally low con us can be dem on strated on m yelogram /CT or on MRI. MRI also dem on - st rates th e lipom atous m ass (h igh sign al on T1W I, low sign al on T2WI). All patien ts sh ould h ave pre-op urological evaluation to docum en t any deficit . Treatm ent Sin ce sym ptom s are due to (1) teth erin g of th e spin al cord, especially durin g grow th spurts, an d (2) com pression due to progressive deposition of fat, especially durin g periods of rapid w eigh t gain ; th e goals of surgery are to release th e teth erin g an d reduce th e bulk of fat t y t um or. Sim ple cosm etic t reat m en t of th e subcutan eous fat pad does n ot preven t n eurologic deficit, an d m ay m ake later definitive repair m ore di cult or im possible. Surgical treatm en t is in dicated w h en th e patien t reach es 2 m on th s of age, or at th e t im e of diag- n osis if th e pat ien t presen ts later in life. Adjun cts to surgical treatm en t in clude evoked poten tial m on itorin g an d laser. Overall, w ith surger y, 19% w ill im prove, 75% w ill be un ch an ged, an d 6% w ill w orsen . Foot deform ities often progress regardless.

270 Developm ental Anom alies Surgical technique (m odified) See referen ce.19 1. m obilize th e subcutan eous m ass, it fun n els dow n th rough th e deep fascia 2. open last in tact ver tebral arch (w ork from n orm al dura) 3. identify th e fibrovascular ban d that crosses the m ost cephalic w idely bifid lam ina 4. sect ion in g th e fibrovascular ban d frees th e dural tube an d releases th e sh arp kin k in th e superi- or surface of th e m en in gocele 5. takin g care to preserve dorsal nerve roots, the dura is incised anterior to the dura-lipom a ju n ct io n 6. sim ilar procedure is carried out w ith arachnoid m em brane 7. dural/arachnoid incision s are continued around entire extent of teth ered conus 8. cord an d placode are un teth ered; m on itorin g tech n iques described in Teth ered cord syn drom e (p.272) are an option 9. subtotal rem oval of lipom a: lipom a is then trim m ed as com pletely as possible, intentionally leavin g som e fat beh in d to avoid injur y to dorsal surface of placode. Superior exten sion alon g dorsal surface of cord or in to cen tral can al is debulked as m uch as is safely possible 10. th e placode is reform ed in to a closed n eural tube 11. close th e pial m argin s 12. th e dura is closed (prim arily if possible, or using fascia lata graft if too m uch ten sion is placed on folded placode) 16.2.5 Derm al sinus General inform at ion A t ract begin n ing at th e skin surface, lin ed w ith epith elium . Usually located at eith er en d of n eural t ube: ceph alic or caudal. Most com m on location is lum bosacral. Probably results from failure of th e cutan eous ectoderm to separate from th e n euro-ectoderm at th e tim e of closure of th e n eural g r o ove .2 Spinal derm al sinus General inform ation May appear as a dim ple or as a sin us, w ith or w ith out h airs, usually ver y close to m idlin e, w ith an open in g of on ly 1–2 m m . Surroun din g skin m ay be n orm al, pigm en ted (“port w in e” discolorat ion ), or distorted by an un derlyin g m ass. Th e sin us m ay term in ate superficially, m ay con n ect w ith th e coccyx, or m ay t raverse betw een n orm al vertebrae or th rough bifid spines to th e dural tube. It m ay w iden at any poin t alon g its path to form a cyst; called an epiderm oid cyst if lin ed w ith stratified squam ous epith elium an d con tain - in g on ly keratin from desquam ated epith elium , or called a derm oid cyst if also lin ed w ith derm is (con tain in g skin appen dages, such as h air follicles an d sebaceous glan ds) an d also con tain in g sebum and hair. Alth ough in n ocuous in appearan ce, th ey are a poten tial path w ay for in tradural in fect ion w h ich 1 6 m ay result in m en in gitis (som etim es recurren t) an d/or in trath ecal abscess. Less serious, a local in fec- t ion m ay occur. Th e lin in g derm is con tains n orm al skin appen dages w h ich m ay result in h air, sebum , desquam ated epith elium an d ch olesterol, w ith in th e t ract . As a result , th e con ten ts of th e sin us tract are irritating and can cause a sterile (chem ical) m en in gitis w ith possible delayed a ra chnoiditis if it enters the dural space. In ciden ce of a presum ed sacral sin us (a dim ple w h ose bottom could n ot be seen on skin retrac- t ion ): 1.2%of n eon ates.24 Derm al sin uses are sim ilar but dist in ct from p ilon id al cyst s w h ich m ay also be congen ital (alth ough som e auth ors say th ey are acquired), con tain h air, are located superficial to th e postsacral fascia, an d m ay becom e in fected. If th e tract expan ds in trath ecally to form a cyst, th e m ass m ay presen t as a teth ered cord or as an in t radural tum or. Bladder dysfun ct ion is usually th e first m an ifestation . Th e tract from a spin al derm al sin us alw ays courses ceph alad as it dives inw ard from th e surface. An occipital sin us m ay pen etrate th e skull an d can com m un icate w ith derm oid cysts as deep as th e cerebellum or fourth ven tr icle. Eva lu a t io n Th ese t ract s are NOT to be probed or injected w ith con trast as th is can precipitate in fect ion or sterile m eningitis.

Prim ary Spinal Anom alies 271 Exam is directed tow ards detect in g abn orm alit ies in sph in cter fun ct ion (an al an d urin ary), lum - bosacral reflexes, an d low er extrem it y sen sat ion an d fun ct ion . Radiologic evaluation W h en seen at birth , ultra sound is th e best m ean s to evaluate for spin a bifida an d a possible m ass inside the can al. If seen in itially follow in g bir th , an MRI sh ould be obtain ed. Sagittal im ages m ay dem on strate th e t ract an d its poin t of attach m en t. MRI also optim ally dem on strates m asses (lipom as, epiderm oids…) w ithin the canal. Plain x-rays an d CT are un able to dem on strate th e fin e t ract w h ich m ay exist bet w een th e skin and the dura. Plain x-rays m ust be don e w h en em barking on surger y as part of operative planning, as prepara- tion for th e possibilit y of a com plete lam in ectom y. Treatm ent Sin uses above th e lum bosacral region sh ould be surgically rem oved. More caudally located sin uses are sligh tly con troversial. Alth ough ≈ 25% of presum ed sacral sin uses seen at birth w ill regress to a deep dim ple on follow -up (tim e n ot specified), it is recom m en ded th at all derm al sin uses sh ould be surgically explored an d fully excised pr ior to th e developm en t of n eurologic deficit or sign s of in fec- t ion . Th e results follow in g in t radural in fect ion are n ever as good as w h en un der taken prior to in fec- t ion . Surgery w ith in th e w eek of diagn osis is appropriate. Sin uses th at term in ate on th e t ip of th e coccyx rarely pen etrate th e dura, an d m ay n ot n eed to be treated un less local in fect ion occurs. Surgical technique An ellipse is cut aroun d th e open in g, an d th e sin us is follow ed deep un t il th e term in ation of th e tract is en coun tered. Careful in sertion of a lacrim al duct probe un der direct vision m ay facilitate excision w ith out violat in g th e tract . If th e tracts pen etrates th e spin e, lam in ectom y m ust be perform ed an d th e t ract follow ed to its full exten t (even if n ecessar y to exten d th e lam in ectom y to T12). An extra- dural cyst m ay be presen t. If th e tract en ters th e dura, it usually does so in th e m idlin e, an d in th ese cases th e dura sh ould be open ed an d in spected. Extrem e care is taken to preven t spillin g th e con - ten ts into the subdural space. Cranial derm al sinus General inform ation Stalk begin s w ith a dim ple in th e occipital or n asal region . Cutan eous st igm ata of h em angiom a, sub- cutan eous derm oid cyst, or abn orm al h air form ation m ay occur. Occipital sin uses exten d caudally, and if they enter the skull, they do so caudal to th e torcular heroph ili. Presen tation m ay include recurren t bacterial (usually S. aureus) or aseptic m en in gitis. Evaluation sh ould in clude MRI to look for in tracran ial exten sion an d associated an om alies, in cluding an in tracran ial derm oid cyst. Treatm ent 16 W h en operatin g on a cran ial derm al sin us, use a sagittally based in cision to perm it deep exploration . Th e tract m ust be follow ed com pletely. Be prepared to en ter th e posterior fossa. 16.3 Klippel-Feil syndrom e 16.3.1 General inform at ion Congen ital fusion of t w o or m ore cer vical vertebrae. Ran ges from fusion of on ly th e bodies (congen - ital block vertebrae) to fusion of th e en tire vertebrae (in cludin g posterior elem en ts). Results from failure of n orm al segm en tat ion of cer vical som ites betw een 3–8 w eeks gestation . Involved ver tebral bodies are often flatten ed an d associated disc spaces are absen t or hypoplastic. Hem ivertebrae m ay also occur. Neural foram in a are sm aller th an n orm al an d oval. Cer vical sten osis is rare. Com plete absence of th e posterior elem en ts w ith an en larged foram en m agn um an d fixed hyperexten sion pos- t ure is called in ien ceph aly an d is rare. In ciden ce of Klippel-Feil is un kn ow n due to its rarit y an d th e fact th at it is frequen tly asym ptom atic. May occur in conjun ct ion w ith oth er congen ital cer vical spin e an om alies such as basilar im pres- sion an d atlan to-occipital fusion .

272 Developm ental Anom alies 16.3.2 Present at ion Classic clin ical triad (all 3 are presen t in < 50%): 1. low posterior hairline 2. shortened neck (brevicollis) 3. lim itation of n eck m otion (m ay n ot be evident if < 3 ver tebrae are fused, if fusion is lim ited on ly to th e low er cer vical levels,25 or if hyperm obilit y of n on fu sed segm en ts com pen sates). Lim itation of m ovem en t is m ore com m on in rotation th an flexion -exten sion or lateral ben ding Oth er clin ical association s in clude scoliosis in 60%, facial asym m et r y, tort icollis, w ebbing of th e n eck (called pter ygium colli w h en severe), Sprengel’s deform it y in 25–35% (raised scapula due to failure of th e scapula to properly descen d from its region of form ation h igh in th e n eck to its n orm al posi- t ion about th e sam e tim e as th e Klippel-Feil lesion occurs), syn kin esis (m irror m otion s, prim arily of h an ds but occasion ally arm s also) an d less com m on ly facial n er ve palsy, ptosis, cleft or h igh arch ed palate. System ic congenital abn orm alit ies m ay also occur in cludin g: gen itourin ar y (th e m ost fre- quen t being un ilateral absen ce of a kidn ey), cardiopulm on ar y, CNS, an d in ≈ 30%deafn ess26 (due to defect ive developm en t of th e osseous in n er ear). No n eurologic sym ptom s h ave ever been directly attributed to th e fused vertebrae, h ow ever sym ptom s m ay occur from n on fused segm en ts (less com m on in sh ort-segm en t fusion s) w h ich m ay be hyperm obile possibly leading to instabilit y or degen erative arthritic changes. 16.3.3 Treat m ent Usually directed at detect in g an d m an agin g th e associated system ic an om alies. Pat ien ts sh ould h ave cardiac evaluation (EKG), CXR, an d a ren al ult rasoun d. Serial exam in ation s w ith lateral flexion -ex- ten sion lateral C-spin e x-rays to m on itor for in stabilit y. Occasion ally, judicious fusion of an un stable n on fu sed segm en t m ay be n eeded at th e risk of furth er loss of m obilit y. See also recom m en dation s regardin g ath letic com petition (p. 937). 16.4 Tet hered cord syndrom e 16.4.1 General inform at ion Abn orm ally low con us m edullaris. Usually associated w ith a sh or t, th icken ed filum term in ale, or w ith an in t radural lipom a (oth er lesion s, e.g. lipom a exten din g th rough dura, or diastem atom yelia are con sidered as separate en tities). Most com m on in m yelom en ingocele (MM). Diagn osis m ust be m ade clin ically in MM, as alm ost all of th ese patien ts w ill h ave teth erin g radiograph ically. 16.4.2 Present at ion Presen ting sign s an d sym ptom s in patien ts w ith teth ered cord are sh ow n in Table 16.2. 16 16.4.3 Myelom eningocele pat ient s If a MM pat ien t h as in creasing scoliosis, in creasing spast icit y, w orsen ing gait (in th ose previously am bulatory), or deteriorating urodynam ics28: ● alw ays m ake sure th at th ere is a w orkin g sh un t w ith n orm al ICP ● if pain ful, sh ould be con sidered teth ered cord un til proven oth erw ise ● if pain less, sh ould be con sidered syrin gom yelia un til proven oth erw ise ● m ay be due to brain stem com pression – see sym ptom atic Ch iari II m alform at ion (p. 284) – requir- in g posterior fossa decom pression 16.4.4 Scoliosis in t et hered cord Progressive scoliosis m ay be seen in conjun ction w ith teth ered cord. Early un teth erin g of th e cord m ay result in im provem en t of scoliosis, h ow ever, un teth erin g m ust be don e w h en th e scoliosis is m ild. W h en cases of ≤ 10° scoliosis w ere un teth ered, 68% h ad n eurologic im provem en t an d th e rem ain ing 32%w ere stabilized, w h ereas w h en scoliosis is severe (≥ 50°) ≈ 16%deteriorated.

Prim ary Spinal Anom alies 273 Table 16.2 Presenting signs and sym ptom s27 (p 1331–2) % Fin d in g 54% cutaneous findings ● 22% ● hypertrichosis ● 15% ● sub-Q lipom a (no intraspinal extension) ● 17% ● miscellaneous (hem angiom atous discoloration, dermal sinus, m ultiple m anifestations) 93% gait difficult y with LE weakness 63% visible muscle atrophy, short limb, or ankle deform it y 70% sensory deficit 40% bladder dysfunction 4% bladder dysfunction as only deficit 37% pain in back, leg, or foot arches 29% scoliosis or kyphosisa 98% posterior spina bifida (lum bar or sacral) ahigh incidence of scoliosis and kyphosis due to inclusion of series by Hoffm an 16.4.5 Tet hered cord in adult s General inform at ion Alth ough m ost cases of teth ered cord presen t in ch ildh ood, cases of adult teth ered cord also occur (≈ 50 publish ed cases as of 1982). For com parison of adult an d ch ildh ood form s, Table 16.3 Evaluat ion Radiograph ically: low con us m edullaris (below L2) an d th icken ed filum term in ale (defin ition of th icken ed filum : n orm al diam eter < 1 m m ; diam eters > 2 m m are path ological). NB: apparen t filum diam eter on CT-m yelogram m ay var y w ith con cen tration of con trast m aterial. It is di cult to di eren tiate a teth ered cord from a con gen itally low lying con us (filum diam eter is gen erally n orm al in th e latter). 16.4.6 Pre-op evaluat ion 16 Pre-operative cystomet rogra m is stron gly recom m en ded, especially if th e pat ien t seem s con tin en t (postoperative ch anges in bladder fun ct ion are n ot un com m on , possibly due to stretch ing of th e low - er fibers of the cauda equina). Surgical t reat m ent If th e on ly abn orm alit y is a th icken ed, sh orten ed filum , th en a lim ited lum bosacral lam in ectom y m ay su ce, w ith division of the filum once iden tified. If a lipom a is foun d, it m ay be rem oved w ith th e filum if it separates easily from n eural t issues. Dist inguishing feat ures of t he filum t erm inale int raoperat ively Th e filum is di eren tiated from n er ve roots by presen ce of ch aracterist ic squiggly vessel on surface of filum . Also, un der th e m icroscope, th e filum h as a distin ct ively w h iter appearan ce th an th e n er ve roots, an d ligam en tous-like stran ds can be seen run n ing th rough it. NB: in tra-op electrical st im ula- t ion an d recordin g of an al sph in cter EMG are m ore defin itive.

274 Developm ental Anom alies Table 16.3 Com parison of childhood and adult tethered cord syndrom e29 Fin d in g Childhood tethered cord Adult tethered cord pain uncomm on; usually in back and legs, not present in 86%, often peri-anal & peri-anal nor perineal perineal; diffuse & bilateral; occasion- ally shock-like foot deform ities com mon early; usually progressive cavova- not seen rus deform it y (club foot) progressive spinal de- com mon; usually progressive scoliosis uncomm on (< 5%) fo rm it y m otor deficits com mon; usually gait abnorm alities & re- usually presents as leg weakness gression of gait training urological sym ptoms common; usually continuous urinary drib- com mon; usually urinary frequency, bling, delayed toilet training, recurrent UTIs, urgency, sensation of incom plete enuresis em pt ying, stress incontinence, over- flow incontinence trophic ulcerations relatively common in LEs rare cutaneous stigm ata of present in 80–100% (tuft of hair, dim ple, present in < 50% dysraphism capillary angiom a (naevus flamm eus) aggravating factors growth spurts traum a, maneuvers associated with stretching conus, lum bar spondylosis, disc herniation, spinal stenosis From J Neurosurg, D. Pang and J.E. Wilberger, Vol. 57, pp. 40, 1982, with perm ission. Out com e In MM, it is usually im possible to perm an en tly un teth er a cord, h ow ever, in a grow in g MM ch ild, it m ay be th at after 2–4 un teth erings th at th e ch ild w ill be fin ish ed grow in g an d teth erin g m ay cease to be a problem . Cases th at are un teth ered early in ch ildh ood m ay recur later, especially durin g th e adolescen t grow th -spurt. In ciden ce of post-op CSF leak: 15%. Adult form : surgical release is usually good for pain relief. How ever, it is poor for return of bladder fun ct ion . 16.5 Split cord m alform at ion 16.5.1 General inform at ion 1 6 Th ere is n o un iform ly accepted n om en clature for m alform ation s ch aracterized by duplicate or split spinal cords. Pang et al.30 h ave proposed th e follow in g. Th e term split cord m alform ation (SCM) sh ould be used for all double spinal cords, all of w h ich appear to have a com m on em bryologic etiology. 16.5.2 Type I SCM Defin ed as t w o h em icords, each w ith its ow n cen tral can al an d surroun din g pia, each w ith in a sepa- rate dural t ube separated by a dural-sh eath ed rigid osseocart ilagin ous (bony) m edian sept um . Th is h as often (but n ot con sisten tly) been referred to as diastem atom yelia. Th ere are abn orm alit ies of th e spine at th e level of th e split (absen t disc, dorsal hypert roph ic bon e w h ere th e m edian “spike” attach es).31 Tw o-th irds h ave overlyin g skin abn orm alit ies in cludin g: n evi, hypertrich osis (tuft of h air), lipom as, dim ples or h em angiom as. Th ese patien ts often h ave an d an orth opedic foot deform it y (n eurogen ic h igh arch es). Treatm ent: sym ptom s are m ost com m on ly due to teth ering of th e cord; an d are usually im proved by un teth ering. In addit ion to un teth erin g, th e bony sept um m ust be rem oved an d th e dura recon sti- t uted as a sin gle tube (th ese spin es are often ver y distor ted an d rotated, th erefore start at n orm al an atom y an d w ork tow ards defect ). DO NOT cut th e teth ered filum un t il a fter th e m edian septum is rem oved to avoid having the cord retract up against septum .

Prim ary Spinal Anom alies 275 16.5.3 Type II SCM Con sists of tw o h em icords w ith in a single dural t ube, separated by a n on rigid fibrous m edian sep - t um . Th is h as som etim es been referred to as diplom yelia. Each h em icord h as n er ve roots arisin g from it. Th ere is usually n o spin e abn orm alit y at th e level of th e split, but th ere is usually spin a bifida occulta in the lum bosacral region. Treatm en t: con sists of un teth ering th e cord at th e level of th e spin a bifida occulta, an d occasion - ally at th e level of th e split.31 16.6 Lum bosacral nerve root anom alies Congen ital an om alies of n er ve roots are rare. Th is possibilit y sh ould be con sidered in cases of failed back surgery for h ern iated disc. Classification system of Can n on et al.32 1. Type 1 an om alies: in clude conjoin ed n er ve root (2 n er ve roots arise from a com m on dural sh eath ). Th ey separate at various distan ces from th e th ecal sac, an d exit th rough th e sam e or sep - arate n eural foram in a. Neurosurgeon s n eed to be aw are of th is an om aly to avoid in adverten t injur y e.g. durin g surgery for h ern iated disc 2. Type 2 an om alies: 2 n er ve roots exit th rough on e foram en . Varian ts33: a) leaves an un occupied n eural foram en b) all foram in a occupied, but on e foram en h as 2 n er ve roots 3. Type 3 an om alies: adjacen t n er ve roots are con n ected by an an astom osis Re fe r e n ce s [15] Larson SJ, San ces A, Ch risten son PC. Evoked Som a- 16 tosen sory Poten tials in Man . Arch Neurol. 1966; [1] Takah ash i S, Morikaw a S, Egawa M, Saruh ash i Y, 15:88–93 Matsusu e Y. Magn et ic reson an ce im agin g-gu id ed percutan eou s fen estration of a cer vical in trad ural [16] Hein z ER, Rosen baum AE, Scar TB, Reigel DH, et al. cyst. Case report. J Neurosurg. 2003; 99:313–315 Teth ered Spin al Cord Follow in g Men ingom yelocele [2] Matson DD. Neurosurgery of In fan cy an d Ch ild - Repair. Radiology. 1979; 131:153–160 h ood. 2nd ed. Sprin gfield: Charles C Th om as; 1969 [17] Scott RM, Wolper t SM, Bartoshesky LE, Zim bler S, [3] van Tu lder MW, Assen delft W J, Koes BW , Bou ter Klauber GT. Derm oid tum ors occurrin g at the site of LM. Spin al rad iograph ic fin d in gs an d n on sp ecific previous m yelom en in gocele repair. J Neurosurg. low back pain . A system atic review of observation al 1986; 65:779–783 st ud ies. Spin e. 1997; 22:427–434 [18] Em er y JL, Len d on RG. Lip om as of th e Caud a Equin a an d Oth er Fatt y Tum ors Related to Neu rosp in al Dys- [4] Stein berg EL, Luger E, Arbel R, Men ach em A, Dekel rap h ism . Dev Med Ch ild Neurol. 1969; 11:62–70 S. A com parat ive roen tgen ograph ic an alysis of th e [19] Naid ich TP, McLon e DG, Mu tlu er S. A n ew u n d er- lum bar spin e in m ale arm y recruits w ith an d w ith - stan din g of dorsal dysraphism w ith lipom a (lipo- out lower back p ain . Clin Rad iol. 2003; 58:985–989 m yelosch isis): radiologic evaluation an d surgical [5] Avrah am i E, Frish m an E, Frid m an Z, Azor M. Spin a correct ion . AJNR. 1983; 4:103–116 bifid a occulta of S1 is n ot an in n ocen t fin d in g. [20] Uch in o A, Mori T, Oh n o M. Th icken ed fatt y filu m Spine. 1994; 19:12–15 term in ale: MR im agin g. Neuroradiology. 1991; [6] Lorber J, Ward AM. Spin a Bifid a - A Van ish in g Nigh t- 33:331–333 m are? Arch Dis Ch ild. 1985; 60:1086–1091 [21] Brow n E, Matth es JC, Bazan C, III, Jin kin s JR. Preva- [7] Stein SC, Sch ut L. Hyd rocep h alu s in Myelom en in go- lence of in ciden tal in traspin al lipom a of th e lum bo- cele. Ch ild s Brain . 1979; 5:413–419 sacral sp in e as d eterm in ed by MRI. Sp in e. 1994; 19:833–836 [8] Crem er R, Kle in e- Diep e n b ru ck U, Hop p e A, Blaker [22] Bruce DA, Sch ut L. Spin al Lipom as in In fan cy an d F. Lat ex alle rgy in sp in a b ifid a p at ien t s–p reven - Ch ild h ood . Ch ilds Brain . 1979; 5:192–203 t ion by p rim ar y p rop h yla xis. Allergy. 1 9 98 ; [23] Sato K, Sh im oji T, Sum ie H, et al. Surgically Con- 53:709–711 firm ed Myelograp h ic Classification of Con gen ital In traspin al Lipom a in th e Lum bosacral Region . [9] Sh arrard W JW, McLau rin RL. In : Assessm en t of th e Ch ild s Nerv Syst. 1985; 1:2–11 Myelom en in gocele Ch ild . Myelom en in gocele. New [24] Powell KR, Ch err y JD, Horigan TJ, et al. A Prospect ive York: Gru n e an d St ratton ; 1977:389–410 Search for Con genital Derm al Abnorm alities of Cra- [10] Sh arrard WJW . Th e Segm en tal In n er vation of th e n iospin al Axis. J Pediatr. 1975; 87:744–750 Low er Lim b Muscles in Man . An n R Coll Su rgeon s [25] Gray SW, Rom ain e CB, Skan dalakis JE. Con gen ital (En gl). 1964; 34:106–122 Fusion of th e Cer vical Ver tebrae. Surg Gynecol [11] Epstein NE, Rosen th al RD, Zito J, et al. Sh u n t Place- Obstet. 1964; 118 m en t an d Myelom en in gocele Rep air: Sim ultan eou s [26] Hen singer RN, Lan g JR, MacEw en GD. Klip pel-Feil versus Sequen tial Sh un tin g. Ch ilds Ner v Syst. 1985; Syn drom e: A Con stellation of Associated Anom alies. 1:145–147 J Bon e Join t Surg. 1974; 56A [27] Youm an s JR. Neurological Surgery. Ph iladelphia [12] Hu bballah MY, Ho m an HJ. Early Repair of Myelo- 1982 m en in gocele an d Sim u ltan eou s In sert ion of VP [28] Park TS, Cail W S, Maggio W M, Mitch ell DC. Progres- Sh u n t: Tech n iqu e an d Resu lts. Neurosurgery. 1987; sive Sp asticit y an d Scoliosis in Ch ild ren w ith Myelo- 20:21–23 m enin gocele: Radiological Invest igation an d [13] McLon e DG. Tech n iqu e for Closu re of Myelom en in - Surgical Treatm en t . J Neurosurg. 1985; 62:367–375 gocele. Childs Brain . 1980; 6:65–73 [14] Ram os E, Marlin AE, Gaskill SJ. Con gen ital derm oid tum or in a child at in itial m yelom en in gocele clo- sure: an etiological discussion . J Neurosurg Ped ia- trics. 2008; 2:414–415

276 Developm ental Anom alies [29] Pang D, W ilberger JE. Teth ered Cord Syn d rom e in [32] Can n on BW , Hu n ter SE, Picaza JA. Nerve-root Ad ults. J Neurosurg. 1982; 57:32–47 an om alies in lum bar-disc surger y. J Neurosurg. 1962; 19:208–214 [30] Pang D, Dias MS, Ah ab -Barm ad a M. Sp lit Cord Mal- form ation : Part I: A Unified Th eor y of Em bryogen e- [33] Neid re A, MacNab I. An om alies of th e lum bosacral sis for Dou ble Sp in al Cord Malform ation s. n er ve roots. Review of 16 cases an d classification . Neurosurger y. 1992; 31:451–480 Spin e. 1983; 8:294–299 [31] Ho m an HJ. Com m en t on Pang D, et al.: Split Cord Malform ation : Part I: A Un ified Th eor y of Em br yo- gen esis for Double Spin al Cord Malform ations. Neu- rosu rgery. 1992; 31 16

Prim ary Craniospinal Anom alies 277 17 Prim ary Craniospinal Anom alies 17.1 Chiari m alform at ions 17.1.1 General inform at ion Th e term “Ch iari m alform ation ” (after path ologist, Han s Ch iari) is preferred for t ype 1 m alform a- t ion s, w ith th e com m on ly used term “Arn old-Ch iari m alform ation” reserved for t ype 2 m alform at ion . Th e Ch iari m alform ation s con sists of four t ypes of h in dbrain abn orm alit ies, probably un related to each oth er. Th e m ajorit y of Ch iari m alform ation s are t ypes 1 or 2 Table 17.1), a ver y lim ited n um - ber of cases com prise th e rem ain ing t ypes. Ch iari zero is a n ovel con dition (p. 286). 17.1.2 Type 1 Chiari m alform at ion General inform at ion Key concept s ● a heterogeneous entit y with the common feature of im paired CSF circulation through the foramen magnum ● m ay be congenital or acquired ● evaluation: MRI of brain and cervical spine (to R/O syringomyelia). Cine MRI to evaluate CSF flow through foramen m agnum in uncertain cases ● cerebellar tonsillar herniation on MRI: criteria vary, > 5 mm below the foramen magnum is often cited, but is neither essential nor diagnostic of the condition ● treatment, when indicated, is surgical, but aspects of what that surgery should entail are contro- versial (enlargement of foram en magnum is usually involved) ● associated with syringomyelia in 30–70%which almost always improves with treatment of the Chiari m alformation AKA prim ar y cerebellar ectopia,2 AKA adult Ch iari m alform at ion (sin ce it ten ds to be diagn osed in th e 2n d or 3rd decade of life). A h eterogen eous group of con dition s, w ith th e un derlying com m on al- it y of disruption of n orm al CSF flow th rough th e foram en m agn um (FM). Som e cases are congen ital, but oth ers are acquired (th is sect ion is kept h ere un der developm en tal for h istorical an d organ iza- tional reasons). Table 17.1 Comparisons of Chiari t ype 1 and 2 anomalies (adapted1) Fin d in g Chiari t ype 1 Chiari t ype 2 (p. 284) (see below) 17 caudal dislocation of medulla unusual yes caudal dislocation into cervical canal t o n sils inferior verm is, medulla, 4th ve n t ricle spina bifida (myelomeningocele) may be present rarely absent hydrocephalus may be absent rarely absent medullary “kink” absent present in 55% course of upper cervical nerves usually norm al usually cephalad usual age of presentation young adult infancy usual presentation cervical pain, suboccipital H/A progressive hydrocephalus, respiratory distress

278 Developm ental Anom alies Classically d escr ibed as a rare abn or m alit y rest r icted to cau d al d isp lacem en t of cerebellu m w ith ton sillar h ern iat ion below t h e foram en m agn u m (below for cr iter ia) an d “p e g-like elon ga- t ion of ton sils.” Un like Ch iari t yp e 2, t h e m ed u lla is n ot cau d ally d isp laced (som e au t h ors d is- agree on this poin t3), th e brainstem is n ot involved, low er cranial ner ves are n ot elon gated, and u p p er ce r vical n er ves d o n ot cou r se cep h alad . Syrin gom yelia of th e sp in al cord is p rese n t in 30– 70%.4 Tru e h yd rom yelia p rob ab ly d oesn ’t occu r; CSF flow h as n ot been d ocu m en ted in m an , an d it is gen erally n ot possible to find com m un icat ion bet w een the syrinx and th e cen tral can al in Ch iar i 1 p at ien t s. Hyd rocep h alu s occu rs in 7–9% of p at ien t s w it h Ch iar i t yp e 1 m alfor m at ion an d syringom yelia.4 Cerebellar ton sil descen t below FM w ith im paction , w h ile com m on , is n o lon ger a sin e qua n on of diagn osis. Associat ions May be associated w ith 1. a sm all posterior fossa a) un derdevelopm en t of th e occipital bon e due to a defect in th e occipital som ites origin atin g from th e para-axial m esoderm b) low lying ten torium (th e roof of th e p -fossa) c) th icken ed or elevated occipital bon e (th e floor of th e p -fossa) d) space occupyin g lesion in p -fossa: arach n oid cyst (retrocerebellar or supracerebellar5), tum or (e.g. FM m en in giom a or cerebellar ast rocytom a), hyper vascular dura 2. h as been described w ith just about anyth in g th at takes up in t racran ial space a) chronic subdural hem atom as b) hydrocephalus 3. follow in g lum boperiton eal sh un t (p.418) or m ult iple (traum atic) LPs6: acquired Ch iari 1 m alfor- m ation (m ay be asym ptom atic) 4. arach n oid w eb or scar or fibrosis aroun d brain stem an d ton sils n ear FM 5. abn orm alit ies of th e upper cer vical spin e a) hyperm obility of the craniovertebral junction b) Klippel-Feil syn drom e c) occipitalization of th e atlas d) an terior in den tat ion at foram en m agn um : e.g. basilar invagin at ion or retroversion of th e odon toid process 6. Eh lers-Dan los syn drom e 7. cran iosyn ostosis: especially cases involving all sutures 8. retain ed rh om boid roof: rare Epidem iology Average age at presentation is 41 years (ran ge: 12–73 yrs). Sligh t fem ale prepon deran ce (fem ale: m ale = 1.3:1). Average durat ion of sym ptom s clearly related to Ch iari m alform at ion is 3.1 yrs (range: 1 m on th -20 yrs); if n on specific com plain ts, e.g. H/A, are in cluded, th is becom es 7.3 years.7 Th is laten cy is probably low er in th e MRI era. Clin ica l 17 Clinical correlates Pat ien ts w ith Ch iari t ype 1 m alform at ion m ay presen t due to any or all of th e follow in g: 1. com pression of brain stem at th e level of th e foram en m agn um 2. hydrocephalus 3. syrin gom yelia 4. isolat ion of th e in tracran ial pressure com par t m en t from th e spin al com part m en t causin g tran si- en t elevation s of ICP in tracran ial pressure 5. 15–30%of pat ien ts w ith adult Ch iari m alform at ion are asym ptom atic8 Sym ptom s Th e m ost com m on sym ptom is pain (69%), especially h eadach e w h ich is usually felt in th e suboccipi- tal region Table 17.2). H/A are often brough t on by n eck exten sion or valsalva m an euver. Weakn ess is also prom in en t, especially un ilateral grasp. Lh erm it te’s sign m ay also occur. Low er extrem it y involvem en t usually con sists of bilateral spasticit y.

Prim ary Craniospinal Anom alies 279 Table 17.2 Presenting symptoms in Chiari 1 m alformation (71 cases3) % Sym pt om 69% p a in 34% H/ A 13% neck (suboccipital, cervical) 11% girdle 8% arm 3% leg 56% weakness (1 or m ore lim bs) 52% num bness (1 or m ore lim bs) 40% loss of t em perature sensat ion 15% painless burns 40% unst eadiness 13% d ip lo p ia 8% d ysp h a sia 7% tinnit us 5% vom iting 4% dysart hria m iscellaneous 3% dizziness 3% deafness 3% fa in t in g 3% facial numbness 1% hiccough 1% facial hyperhidrosis Sig n s 17 Dow n beat nystagm us is con sidered a ch aracterist ic of th is con dition . 10%w ill h ave a n orm al n euro- logic exam w ith occipital H/A as th eir on ly com plain t. Som e patien ts m ay presen t prim arily w ith spasticit y. See Table 17.3. Th ree m ain pattern s of clusterin g of sign s3: 1. fora men ma gnum compression syndrome (22%): ataxia, corticospin al an d sen sor y deficits, cerebel- lar sign s, low er cran ial n er ve palsies. 37%h ave severe H/A 2. centra l cord syndrome (65%): dissociated sen sor y loss (loss of pain & tem perature sen sation w ith preser ved touch & JPS), occasion al segm en tal w eakn ess, an d lon g tract sign s (syrin gom yelic syn - drom e9). 11%h ave low er cran ial n er ve palsies 3. cerebellar syndrome (11%): t run cal an d lim b ataxia, nystagm us, dysarth ria Nat ural hist ory Th e n atural h istor y is n ot kn ow n w ith certain t y (on ly 2 reports on “n atural h istor y”). A patien t m ay rem ain stable for years, w ith in term itten t periods of deteriorat ion . Rarely, spon tan eous im prove- m ent m ay occur (debated).

280 Developm ental Anom alies Table 17.3 Presenting signs in Chiari I malform ation (127 patients7) % Sig n hyperactive lower extrem it y reflexes 52% n yst a g m u sa 47% gait disturbance 43% hand atrophy 35% upper extremit y weakness 33% “cape” sensory loss 31% cerebellar signs 27% hyperactive upper extremit y reflexes 26% lower cranial nerve dysfunction 26% Babinski sign 24% lower extrem it y weakness 17% d yse st h e sia 17% fa scicu lat io n 11% Horner’s sign 6% aclassically: downbeat nystagmus on vertical m ovem ent, and rotatory nystagmus on horizontal movem ent; also includes oscillopsia10 Evaluat ion Plain x-rays Of 70 sku ll x-rays, on ly 36%w ere abn orm al (26%sh ow ed basilar im pression , 7%platybasia, an d 1 pa- t ien t each w ith Paget’s an d con cave clivus); in 60 C-spin e x-rays, 35% w ere abn orm al (in cludin g assim ilation of atlas, w iden ed can al, cervical fusion s, agen esis of posterior arch of atlas). MRI MRI of brain an d C-spin e is th e diagn ostic test of ch oice. Easily sh ow s m any of th e classic abn orm al- ities described earlier, in cludin g ton sillar h ern iation , as w ell as hydrosyrin gom yelia w h ich occurs in 20–30% of cases. Also dem on st rates ven tral brain stem com pression w h en presen t. Oth er fin dings include: hydrocephalus, em pty sella. Ton sillar h ern iation : Criteria for th e descen t of th e ton sillar tips below th e foram en m agn um (FM) to diagn ose Ch iari t ype 1 m alform ation h ave gon e th rough a n um ber of recon sideration s. 17 Σ Tonsillar herniation identified radiographically is of limited prognostic value in diagnosing Chiari I m al- form ation, and requires clinical correlation. In itially, > 5 m m w as defin ed as clearly path ologic11 (w ith 3–5 m m bein g borderlin e). Barkovich12 foun d ton sillar position s as sh ow n in Table 17.4, an d Table 17.5 sh ow s th e e ect of utilizing 2 vs. 3 m m as th e low est norm al position. Th e ton sils n orm ally ascen d w ith age13 as sh ow n in Table 17.6

Prim ary Craniospinal Anom alies 281 Table 17.4 Location of cerebellar tonsils below foramen magnum 12 Gr o u p Me a n a Ra n g e n o rm al 1 m m above 8 mm above to 5 m m below Chiari I 13 m m below 3–29 m m below abased on m easurements in 200 normals and 25 Chiari I patients taken in relation to the lower part of the foramen magnum Table 17.5 Criteria for Chiari I12 Sensit ivit y for Chiari I Specificit y for Chiari I Criteria for lowest ext ent of t onsils accept ed as norm al 100% 98.5% 96% 99.5% 2 m m below FM 3 m m below FM Table 17.6 Tonsillar position relative to FM at various ages13 Ag e Norm al 2 S.D.b (years) (m m )a (m m ) 0–9 –1.5 –6 10–19 –0.4 –5 20–29 –1.1 30–39 0.0 –4 40–49 0.1 50–59 0.2 60–69 0.2 70–79 0.6 80–89 1.3 –3 anegative num ber indicates distance below FM bS.D. = standard deviation. Descent > 2 S.D. beyond norm al is suggested as a criteria for tonsillar ectopia Pat ien ts w ith syrin gohydrom yelia w ith out h in dbrain h ern iation th at respon ded to p -fossa 17 decom pression h ave been described14 (so-called “Ch iari zero m alform ation ”). Conversely, 14% of patien ts w ith ton sillar h ern iation > 5 m m are asym ptom atic15 (average exten t of ectopia in th is group w as 11.4 ± 4.86 m m ). Poten tially m ore sign ifican t th an th e absolute ton sillar descen t is th e am oun t of com pression of th e brain stem at th e FM, best appreciated on axial T2W I MRI th rough th e FM. Com plete obliteration of CSF sign al an d com pression of th e brain stem at th e FM by im pacted ton sils is a com m on sign ifi- can t fin ding. Cine MRI AKA CSF flow study. May dem on strate blockage of CSF flow at FM. Not w idely available. Accuracy is n ot h igh , th erefore usually does n ot alter m an agem en t.

282 Developm ental Anom alies Mye lo g r a p h y Gen erally used on ly w h en MRI can n ot be obtain ed. On ly 6% false n egative. It is critical to run th e in trath ecal con trast (dye) all th e w ay up to th e foram en m agn um . Usually com bin ed w ith CT scan . CT Un en h an ced CT is poor for evaluating th e foram en m agn um region due to bony art ifact. It is ver y good at dem on stratin g hydroceph alus (as is MRI). W h en com bined w ith in t rath ecal iodin ated con - t rast (m yelogram ), reliabilit y im proves. Fin dings: ton sillar descen t w ith possible com plete blockage of dye at foram en m agn um . Treat m ent Indications for surgery Sin ce patien ts respon d best w h en operated on w ith in 2 years of th e on set of sym ptom s (below ), early surger y is recom m en ded for sym ptom at ic patien ts. Asym ptom at ic patien ts m ay be follow ed an d operated upon if an d w h en th ey becom e sym ptom atic. Patien ts w h o h ave been sym ptom at ic an d stable for years m ay be con sidered for obser vation , w ith surger y in dicated for sign s of deterioration . Surgical techniques Th e m ost frequen tly perform ed operation is posterior fossa decom pression (suboccipital cran iec- tom y), w ith or w ith out oth er procedures (usually com bin ed w ith dural patch graft in g an d cer vical lam in ectom y of C1, som etim es to C2 or C3). Option s for grafts: sam e in cision (pericran ium ), separate in cision (e.g. or fascia lata), an d allograft (avoided by m any auth ors because of dissat isfaction w ith abilit y to provide w ater-t igh t closure an d because of in fect ious risks). Goals of surger y: decom press th e brain stem an d reestablish n orm al flow of CSF at th e cran iocer- vical junction. Th e patien t is position ed pron e on ch est rolls w ith th e h ead in a Mayfield h ead-h older or in a h orsesh oe h eadrest. Flex th e n eck to open th e in terspace betw een th e occiput an d posterior arch of C1. Th e sh oulders are retracted in feriorly w ith adh esive tape. If a fascia lata graft is to be taken , ele- vate on e th igh on a san dbag. A m idlin e in cision from in ion to ≈ C2 spin ous process is m ade. Th e rem oval of bon e above th e foram en m agn um sh ould be ≈ 3 cm h igh by ≈ 3 cm w ide (keep th e poste- rior-fossa part of th ese operation s sma ll, th e m ain th rust is to open th e foram en m agn um to decom - press th e ton sils an d an upper cer vical lam in ectom y; th e com pression is not in th e p -fossa). Excessive rem oval of occipital bon e m ay allow th e cerebellar h em isph eres to h ern iate th rough th e open in g (\"cerebellar ptosis”), an d create addit ion al problem s. If a pericran ial graft is to be taken , it should be harvested at this tim e to reduce th e am ount of blood en tering the subsequent dural open- in g.16 Pericran ial graft can be procured w ith out exten din g th e in cision about th e in ion using th e tech n ique of Dr. Rober t Ojem an n16 w ith subgaleal dissection an d using a m on opolar cautery w ith a ben t tip to in cise th e periosteum an d th en a Pen field # 1 dissector to free it from th e bon e surface. Open th e dura in a “Y” sh aped in cision , an d excise th e t riangular top flap. CAUTION: th e t ran s- verse sin uses are usually abn orm ally low in Ch iari m alform at ion s. Sut ure th e patch graft to provide m ore room for th e con ten ts (ton sils + m edulla). An opt ion th at is som et im es used in pediatrics is to n ot in itially open th e dura but to lyse con - st rictin g ban ds over th e dura at th e foram en m agn um an d th en an d use in traoperative ult rasoun d to 1 7 determ in e if th ere is adequate room for CSF flow, th e dura is th en open ed on ly if th ere is n ot. Historical procedures that have been appended to th e above: pluggin g the obex (w ith m uscle or teflon ), drain age of syrin x if present (fen estration , usually th rough dorsal root en tr y zon e, w ith or w ith out stent or sh un t), 4th ven t ricular sh un tin g, term in al ven triculostom y, an d open ing foram en of Magen die if obstructed (see referen ce for illustration s9). Curren t recom m en dat ion s are th at th ese or oth er addition al procedures beyon d dural patch graft ing are usually n ot w arran ted. Som e auth ors repeatedly adm on ish not to attem pt to rem ove adh esion s bin din g th e ton sils togeth er (to avoid injurin g vital st ructures, in cludin g PICAs). Oth ers recom m en d cautiously separat- in g th e ton sils an d even sh rin kin g th em dow n w ith bipolar cauter y. In cases w ith ven tral brain -stem com pression , som e auth ors advocate perform ing a t ran soral cli- vus-odon toid resection as th ey feel th ese patien ts m ay poten tially deteriorate w ith posterior fossa decom pression alon e.17 Sin ce th is deterioration w as reversible w ith odon toidectom y, it m ay be rea- son able to perform th is procedure on pat ien ts w h o sh ow sign s of deterioration or progression of basilar im pression on serial MRIs after posterior fossa decom pression .

Prim ary Craniospinal Anom alies 283 Booking t he case : Chiari m alform at ion Also see defaults & disclaim ers (p. 27). 1. position: prone 2. equipment: a) optional microscope b) intra-op Doppler, if used 3. consent: a) procedure: surgery through the back of the neck to open the bone at the base of the skull and to insert a “patch” to make m ore room for the brainstem b) alternatives: non-surgical management is usually not e ective c) com plications: CSF leak, brainstem injury/stroke, apnea, failure to improve syrinx (if present) Operative findings See Table 17.7. Ton sillar h ern iation is presen t in all cases (by defin it ion ); th e m ost com m on position being at C1 (62%). Fibrous adh esion s bet w een dura, arachn oid an d ton sils w ith occlusion of foram in a of Lusch ka an d Magen die in 41%. Th e ton sils separated easily in 40%. Surgical com plicat ions After suboccipital cran iectom y plus C1–3 lam in ectom y in 71 patien ts, w ith dural patch grafting in 69, on e death due to sleep apn ea occurred 36 h rs post-op. Respirator y depression w as th e m ost com - m on post-op com plication (in 10 patien ts), usually w ith in 5 days, m ostly at n igh t. Close respirator y Table 17.7 Operative findings in Chiari I (71 patients3) % Fin d in g 100% t onsillar descent below foramen magnum 4% C1 62% C2 25% C3 3% unspecified level 6% 17 a d h e sio n s 41% syringom yelia 32% dural band (at foram en m agnum or C1 arch) 30% vascular abnorm alit iesa 20% skeletal abnorm alities inverted foram en m agnum 10% keel of bone 3% C1 arch atresia 3% occipitalization of C1 arch 1% cervicom edullary “hum p” 12% avascular abnorm alities: PICA dilated or abnormal course in 8 patients (PICA often descends to lower margin of tonsils9); large dural venous lakes in 3

284 Developm ental Anom alies Table 17.8 Long-term follow-up after surgery for Chiari I malform ation (69 patients, 4 years m ean F/U3) early im provem ent of pre-op sym ptom s 82% percent of above that relapseda 21% early im provem ent of pre-op signs 70% no change from pre-op status 16% worse than pre-op 0 athese patients deteriorated to pre-op status (none deteriorated further) within 2–3 years of surgery; relapse occurred in 30% with foramen magnum com pression syndrome, and in 21% with central cord syndrom e m on itorin g is th erefore recom m en ded.3 Oth er risks of th e procedure in clude: CSF leak, h ern iation of cerebellar h em isph eres, vascular injuries (to PICA…). Operat ive result s See Table 17.8. Pat ien ts w ith pre-op com plain ts of pain generally respon d w ell to surgery. Weakn ess is less respon sive to surgery, especially w h en m uscle atrophy is presen t .17 Sen sat ion m ay im prove w h en th e posterior colum n s are un a ected an d th e deficit is due to spin oth alam ic involvem en t alon e. Rh oton feels th at th e m ain ben efit of operat ion is to arrest progression . Th e m ost favorable results occurred in patien ts w ith cerebellar syn drom e (87%sh ow in g im prove- m en t, n o late deterioration ). Factors th at correlate w ith a w orse outcom e are th e presen ce of atro- phy, ataxia, scoliosis, an d sym ptom s lastin g lon ger th an 2 years.17 17.1.3 Type 2 (Arnold)-Chiari m alform at ion General inform at ion Key concept s ● usually associated with myelomeningocele, often accom panied by hydrocephalus pathology includes: caudally displaced cervicomedullary junction, small posterior fossa, tectal beaking. Is probably not due to tethering ● major clinical findings: swallowing di culties, apnea, stridor, opisthotonos, downbeat nystagmus ● when sym ptomatic: always check the shunt first! Then, consider surgical decom pression (which cannot correct intrinsic brainstem abnormalities) ● cranial and cervical MRI is the diagnostic test of choice. 1 7 Usually associated w ith m yelom en ingocele (MM), or rarely spina bifida occulta. Pat hophysiology Probably does not result from teth erin g of th e cord by th e associated MM. More likely due to prim ar y dysgen esis of th e brain stem w ith m ult iple oth er developm en tal an om alies.18 Major findings Caudally dislocated cer vicom edullar y jun ct ion , pon s, 4th ven tricle an d m edulla. Cerebellar ton sils located at or below th e foram en m agn um . Replacem en t of n orm al cervicom edullar y jun ction flexure w ith a “kin k-like deform it y.” Oth er possible associated fin din gs: 1. beaking of tectum 2. absence of th e septum pellucidum w ith enlarged interthalam ic adh esion: absen ce of the septum pellucidum is thought to be due to necrosis w ith resorption secondar y to hydroceph alus, an d n ot a congenital absen ce19 (p 178)

Prim ary Craniospinal Anom alies 285 3. poorly m yelin ated cerebellar folia 4. hydrocephalus: present in m ost 5. h eterotopias 6. hypoplasia of falx 7. m icrogyria 8. degen eration of low er cran ial n er ve n uclei 9. bony abnorm alit ies: a) of cervicom edullar y jun ction b) assim ilation of atlas c) platybasia d) basilar im pression e) Klippel-Feil deform it y (p. 271) 10. hydrom yelia 11. cran iolacun ia of th e skull (see below ) Present at ion Fin din gs are due to brain stem an d low er cran ial n er ve dysfun ct ion . On set is rare in adulth ood. Th e presen tation of n eon ates di ers substan t ially from older ch ildren , an d n eon ates w ere m ore likely to develop rapid n eurological deterioration w ith profoun d brain stem dysfun ct ion over a period of sev- eral days th an w ere older ch ildren in w h om sym ptom s w ere m ore in sidious an d rarely as severe.20 Fin din gs in clud e21,20: 1. sw allow in g di cult ies (n eurogen ic dysph agia) (69%).22 Man ifests as poor feedin g, cyan osis dur- in g feedin g, n asal regurgitat ion , prolonged feedin g t im e, or poolin g of oral secretion s. Gag reflex often decreased. More severe in n eon ates 2. apn eic spells (58%): due to im paired ven tilatory drive. More com m on in n eon ates 3. st ridor (56%): m ore com m on in n eon ates, usually w orse on in spiration (abductor an d occasion - ally adductor vocal cord paralysis seen on lar yn goscopy) due to 10th n er ve paresis; usually tran - sient, but m ay progress to respirator y arrest 4. aspirat ion (40%) 5. arm w eakn ess (27%) th at m ay progress to quadriparesis23 6. opisth oton os (18%) 7. nystagm us: especially dow n beat nystagm us 8. weak or absent cry 9. facial w eakn ess Diagnostic evaluat ion Skull film s May dem on strate ceph alofacial disproport ion from congen ital HCP. Cran iolacun ia (AKA lü cken sch ä- del) in 85%(roun d defect s in th e skull w ith sh arp borders, separated by irregularly bran chin g ban ds of bon e; not due to in creased ICP). Low lying in tern al occipital protuberan ce (foresh orten ed posteri- or fossa). En larged foram en m agn um in 70%; elon gation of upper cer vical lam in a.1 CT and/or MRI findings 17 Cran ial an d cer vical MRI is th e diagn ost ic test of ch oice. ● prim ar y findings a) “Z” ben d deform it y of m edulla* b) cerebellar peg c) tectal fusion (“tectal beaking”) d) en larged m assa in term edia (in terth alam ic adh esion )* e) elongation/cervicallization of m edulla f) low attachm ent of ten torium ● associated fin din gs a) hydrocephalus b) syrin gom yelia in th e area of th e cer vicom edullar y jun ct ion (reported in ciden ce in pre MRI era17 ran ges from 48–88%) c) t rapped fourth ven tr icle d) cerebellom edullar y com pression e) agen esis/dysgen esis of corpus callosum * * item s w ith an asterisk are best appreciated on MRI

286 Developm ental Anom alies La r yn g o sco p y Perform ed in patien ts w ith stridor to rule out croup or oth er upper respirator y t ract in fect ion . Treat m ent General inform ation ● in sert CSF sh un t for hydroceph alus (or ch eck fun ct ion of existin g sh un t) ● if n eurogen ic dysph agia, str idor, or apn eic spells occur, expedit ious posterior fossa decom pression is recom m en ded (see below ) (required in 18.7%of MM patien ts21); before recom m en ding decom - pression , always m ake sure th e pat ien t h as a fun ct ion in g sh un t! Surgical decom pression NB: it h as been argued th at par t of th e explan ation for th e poor operative results in in fan ts is th at m any of the neurological fin dings m ay be due in part to intrinsic (uncorrectable) abnorm alities w h ich surgical decom pression can n ot im prove.24,25 A dissen tin g view is th at th e h istologic lesion s are due to ch ron ic brain stem com pression an d concom itan t isch em ia, an d th at expedit ious brain stem decom pression sh ould be carried out w h en any of th e follow in g critical w arn ing sign s develop: neurogenic dyspha gia , str idor, a pneic spells.20 Surgical technique Decom pression of cerebellar ton sils, usually w ith dural graft to decom press dura. Patien ts is placed pron e, w ith th e n eck flexed. A suboccipital cran iectom y is com bin ed w ith a cervical lam in ectom y w h ich m ust be carried dow n to th e bottom of th e ton sillar t ip.23 A th ick con strict in g dural ban d is usually foun d betw een th e C1 arch an d foram en m agn um . Th e dura is open ed in a “Y” sh aped in ci- sion . Caution w h en open in g th e dura above th e level of th e foram en m agn um in in fan ts as th ey h ave a w ell-developed occipital sin us an d m ay h ave large dural lakes.21 DO NOT attem pt to dissect ton sils from un derlying m edulla. In cases w ith a sign ifican t syrin gom yelic cavit y, a syrin go-subarach n oid sh u n t is p laced.20 Trach eostom y (usually tem porary) is recom m en ded if stridor an d abductor lar yn geal palsy w ere presen t pre-op. Close post-op respirator y m on itoring is n eeded for obstruct ion a nd reduced ven tila- tory drive (m ech an ical ven tilation is in dicated for hypoxia or hypercarbia). Out com e 68%h ad com plete or n ear com plete resolut ion of sym ptom s, 12%h ad m ild to m oderate residual def- icits, an d 20%h ad n o im provem en t (in gen eral, n eon ates fared w orse th an older ch ildren ).20 Respirator y arrest is th e m ost com m on cause of m or talit y (8 of 17 pat ien ts w h o died), w ith th e rest due to m en ingit is/ven triculit is (6 patien ts), aspirat ion (2 patien ts), an d biliar y atresia (1 p atien t).21 In follow -up ran ging 7 m os-6 yrs, 37.8%m ortalit y in operated pat ien ts. Pre-op status an d the rapidity of neurologic deterioration w ere the m ost im portant prognostica- tors. Mortalit y rate is 71% in in fan ts h avin g cardiopulm on ar y arrest, vocal cord paralysis or arm w eakness w ithin 2 weeks of presentation; com pared to 23%m ortality in patients w ith a m ore grad- ual deterioration . Bilateral vocal cord paralysis w as a par ticularly poor progn osticator for respon se to surger y.20 17 17.1.4 Ot her Chiari m alform at ions Chiari t ype 0 Pat ien ts w ith syrin gohydrom yelia w ith out h in dbrain h ern iation th at respon d to p -fossa decom pres- sion h ave been described14 (so-called “Ch iari zero m alform ation ”). Chiari t ype 1.5 Obex situated below foram en m agn um , does n ot respon d to suboccipital decom pression w ith or w ithout duroplasty. Chiari t ype 3 Rare. Both th e defin ition an d even th e existen ce are con troversial. Most description s are based on 1 or 2 cases. Origin al descript ion cited dislocation of th e cerebellum below th e foram en m agn um in to

Prim ary Craniospinal Anom alies 287 an occipital en ceph alocele.26 Som e h ave added h ern iation of th e m edulla, fourth ven tricle an d all of th e cerebellum in to an occipital an d h igh cer vical en ceph alocele. Som e h ave sided w ith Raim on di w h o in cluded occipital en ceph aloceles associated w ith caudal displacem en t of th e cerebellum an d m ed u lla.27,28 Progn osis is poor for m ost, as it is usually in com pat ible w ith life. Chiari t ype 4 Origin ally described as cerebellar hypoplasia w ith out cerebellar h ern iation .29 Existen ce as a distin ct clin ical en tit y is debated.26 17.2 Neural t ube defect s 17 17.2.1 Classificat ion General inform at ion Th ere is n o un iversally accepted classification system . Tw o are presen ted below. Lem ire classificat ion A system adapted from Lem ire.30 1. n eurulation defects: n on -closure of th e n eural t ube results in open lesions a) cran iorach isch isis: total dysraph ism . Many die as spon tan eous abor tion b) an en cephaly: AKA exen ceph aly. Due to failure of fusion of th e an terior n europore. Neith er cran ial vault n or scalp covers th e part ially dest royed brain . Un iform ly fatal. Risk of recurren ce in future pregn an cies: 3% c) m eningom yelocele: m ost com m on in lum bar region ● m yelom en ingocele (MM) (p. 265) ● m yelocele 2. postn eurulation defect s: produces skin -covered (AKA closed) lesion s (som e m ay also be con sid- ered “m igration abn orm alit ies”, see below ) a) cran ial ● m icrocephaly: see below ● hydran en ceph aly: loss of m ost of cerebral h em isph eres, replaced by CSF (see below ). Must R/O m axim al hydroceph alus (see below ) ● h oloprosencephaly: see below ● lissen ceph aly: see below ● poren ceph aly: see below to dist in guish from sch izen ceph aly ● agen esis of corpus callosum : see below ● cerebellar hypoplasia/Dan dy Walker syn drom e (p. 256) ● m acroen ceph aly AKA m egalen ceph aly: see below b) spinal ● diastem atom yelia, diplom yelia: see Split cord m alform ation (p. 274) ● hydrom yelia/syrin gom yelia (p. 1144) Migrat ion abnorm alit ies A sligh tly di eren t classification sch em e defin es th e follow in g as abn orm alit ies of n euron al m igra- t ion (som e are con sidered post n eurulation defects, see above): 1. lissen ceph aly: Th e m ost severe n euron al m igration abn orm alit y. Maldevelopm en t of cerebral convolution s (probably an arrest of cort ical developm en t at an early fetal age). In fan ts are severely retarded an d usually don’t sur vive > 2 yrs a) agyria: com pletely sm ooth surface b) pachygyria: few broad & flat gyri w ith sh allow sulci c) polym icrogyria: sm all gyri w ith sh allow sulci. May be di cult to diagn ose by CT/MRI, an d m ay be con fused w ith pachygyria 2. h eterotopia: abn orm al foci of (n on en h an cing) gray m at ter w h ich m ay be located anyw h ere from th e subcort ical w h ite m atter to (m ost com m on ly) th e subepen dym al lin in g of th e ven tricles. May m an ifest as n odules or as a ban d of cortex. An early m igration defect th at results from arrest of radial m igration . Alm ost always presen ts w ith seizures 3. cort ical dysplasia: a cleft th at does n ot com m un icate w ith th e ven t ricle. Heterotopias are com - m on . A m igration abn orm alit y n ot quite as severe as sch izen ceph aly

288 Developm ental Anom alies 4. sch izen cep h aly: a) sin e qua n on : cleft th at com m un icates w ith th e ven t ricle (com m un ication m ay be con firm ed w ith CT cistern ogram if n ecessar y) b) cleft lin ed w ith cort ical grey m atter (often abn orm al, m ay h ave polym icrogyria). Th is dist in - guish es it from p oren cep h aly, a cystic lesion lin ed w ith con n ective or glial tissue th at m ay com m un icate w ith th e ven tricular system , often caused by vascular in farcts or follow in g in tracerebral h em orrh age or pen etrat in g traum a (in cludin g repeated ven tricular pun ct ures) c) t w o form s: ● open lipped: large cleft to ven tricle. Ver y severe form s m ay m im ic hydran en ceph aly (see below ) ● close lipped (w alls fused): look for a dim ple in th e lateral w all of th e lateral ven tricle im m ediately un der th e cort ical cleft (th e appearan ce of w h ich m ay m im ic an en larged su lcu s) d) m ay be unilateral or bilateral e) pia an d arach n oid fuse f) th ere m ay be an “abn orm al” vein th at represen ts a cort ical vein th at n ow looks m edullar y because it follow s th e cortex in to th e cleft) g) absence of septum pellucidum in 80–90% h ) presen tation m ay ran ge from seizures to h em iparesis depen din g on size an d locat ion 17.2.2 Exam ples of neural t ube defect s Hyd r a n e n ce p h a ly General inform ation A post-n eurulation defect . Total or n ear-total absen ce of th e cerebrum (sm all ban ds of cerebrum m ay be con sisten t w ith th e diagn osis31), w ith in tact cran ial vault an d m en in ges, th e in t racran ial cav- it y being filled w ith CSF. Th ere is usually progressive m acrocran ia, but h ead size m ay be n orm al (especially at bir th ), an d, occasion ally, m icroceph aly m ay occur. Facial dysm orph ism is rare. May be due to a variety of causes, th e m ost com m on ly cited is bilateral ICA in farcts (w h ich results in absence of brain tissue supplied by the an terior and m iddle cerebral arteries w ith preservation in th e dist ribution of th e PCA). May also be due to in fect ion (congen ital or n eon atal h erpes, toxoplas- m osis, equine virus). Less a ected in fan ts m ay appear n orm al at birth , but are often hyperirritable an d retain prim itive reflexes (Moro, grasp, an d stepping reflex) beyon d 6 m o. Th ey rarely progress beyon d spon tan eous vow el product ion an d social sm ilin g. Seizures are com m on . Di erentiation from hydrocephalus Progressive en largem en t of CSF spaces m ay occur w h ich can m im ic severe (“m axim al”) hydroceph a- lus (HCP). It is critical to di eren tiate th e t w o sin ce t rue HCP m ay be t reated by sh un tin g w h ich m ay produce som e re-expan sion of th e cort ical m an tle. Many m ean s to distin guish hydran en ceph aly an d HCP h ave been described, in cluding: 1. EEG: sh ow s n o cort ical act ivity in hydran en cephaly (m axim al HCP t ypically produces an abn or- m al EEG, but backgroun d act ivity w ill be presen t th rough out th e brain 31) an d is on e of th e best ways to di erentiate the two 2. CT,32,31 MRI or ultrasoun d: m ajorit y of in t racran ial space is occupied by CSF. Usually do n ot see 1 7 fron tal lobes or fron tal h orn s of lateral ven tricles (th ere m ay be rem n an ts of tem poral, occipital or subfron tal cortex). A str uct ure con sist in g of brain stem n odule (roun ded th alam ic m asses, hypoth alam us) an d m edial occipital lobes sitt in g on th e ten torium occupies a m idlin e position surrounded by CSF. Posterior fossa struct ures are grossly in tact. Th e falx is usually in tact (un like alobar holoprosen ceph aly), an d is n ot th icken ed, but m ay be displaced laterally. In HCP, som e cort ical m an tle is usually iden tifiable 3. t ran sillum in ation of th e skull: in a darken ed room , a brigh t ligh t is placed again st th e surface of th e skull. To tran sillum in ate, th e patien t m ust be < 9 m os old an d th e cort ical m an tle un der th e ligh t source m ust be < 1 cm th ick,33 (p 215) can also occu r if fluid d isplaces th e cortex inw ard (e.g. subdural e usion s). Too in sen sitive to be ver y h elpful 4. an giography: in “classic” cases result in g from bilateral ICA occlusion , n o flow th rough supracli- n oid carotids and a norm al posterior circulation is expected

Prim ary Craniospinal Anom alies 289 Treatm ent Sh un ting m ay be perform ed to con trol h ead size, but un like th e case w ith m axim al hydroceph alus, there is n o restitut ion of the cerebral m antle. Ho lo p r o s e n ce p h a ly AKA arhinencephaly. Failure of the telencephalic vesicle to cleave into two cerebral hemispheres. The degree of cleavage failure ranges from the severe alobar (single ventricle, no interhem ispheric fissure) to sem ilobar and lobar (less severe m alform ations). The olfactory bulbs are usually sm all and the cingulate gyrus rem ains fused. Median faciocerebral dysplasia is com m on, and the degree of severity parallels the extent of the cleavage failure Table 17.9). 80%are associated w ith trisomy (prim arily trisomy 13, and to a lesser extent trisomy 18). Survival beyond infancy is uncom m on, m ost survivors are severely retarded, a m inority are able to function in society. Som e develop shunt dependent hydrocephalus. The risk of hol- oprosencephaly is increased in subsequent pregnancies of the sam e couple. Micr o ce p h a ly Defin ition : h ead circum feren ce m ore th an 2 stan dard deviation s below th e m ean for sex an d gesta- t ion al age. Term s th at are som etim es used syn onym ously: m icrocran ia, m icroceph alus. Not a sin gle en tit y, m any of th e con dition s in Table 17.9 m ay be associated w ith m icroceph aly. It m ay also result from m atern al cocain e abuse.35 It is im por tan t to di eren tiate m icroceph aly from a sm all skull result in g from cran iosyn ostosis in w hich surgical treatm en t m ay provide opport un it y for im proved cerebral developm ent. Ma cr o e n ce p h a ly Adapted.36 (p 109) AKA m acren ceph aly, AKA m egalen ceph aly. Not to be con fused w ith m acroceph aly (p.1403), w h ich is en largem en t of th e skull. Not a sin gle path ologic en tity. An en larged brain w h ich m ay be due to: hypertrophy of gray m atter alone, gray and w hite m atter, presence of additional st ruct ures (glial overgrow th , di use gliom as, h eterotopias, m etabolic storage diseases…). Con dition s in w h ich m acroceph aly m ay be seen in clude: ● n eurocutan eous syn drom es (especially n eurofibrom atosis) ● m egalen ceph aly-capillar y m alform at ion syn drom e (MCAP): an overgrow th syn drom e w ith m ega- len ceph aly (often w ith hydroceph alus, Ch iari m alform ation , polym icrogyria an d seizures), an d capillar y m alform ation s in th e skin (usually on th e face) Brain s m ay w eigh up to 1600–2850 gram s. IQ m ay be n orm al, but developm en tal delay, retardation , spast icit y an d hypoton ia m ay occur. Head circum feren ce is 4–7 cm above m ean . Th e usual sign s of hydrocephalus (fron tal bossing, bulgin g fon tan elle, “sett in g sun ” sign , scalp vein en gorgem en t) are absent . Im aging studies (CT or MRI) sh ow n orm al sized ven t ricles an d can be used to rule out extra- axial fluid collection s. Table 17.9 The five facies of severe holoprosencephaly34 Type of face Facial feat ures Cranium and brain findings cyclopia single eye or partially divided eye in microcephaly; alobar holoprosence- 17 single orbit; arhinia with proboscis phaly ethm ocephaly extrem e orbital hypotelorism; sepa- microcephaly; alobar holoprosence- rate orbits; arhinia with proboscis phaly ce b o ce p h a ly orbital hypotelorism; proboscis-like microcephaly; usually has alobar hol- nose; no m edian cleft lip o p ro se n ce p h a ly with median cleft lip orbital hypotelorism; flat nose microcephaly; sometimes has trigono- cephaly; usually has alobar holopro- sencephaly with median philtrum -premax- orbital hypotelorism; bilateral lateral m icrocephaly; som etimes has trigono- illa anlage cleft lip with m edian process repre- cephaly; semilobar or lobar holopro- senting philtrum -prem axillary an- sencephaly lage; flat nose

290 Developm ental Anom alies 17.2.3 Risk fact ors 1. lack of pren atal folic acid: early adm in istration of folic acid37,38,39 (0.4 m g/d if n o h istor y of n eural tube defects; 4 m g/d in a carrier or w ith previous ch ild w ith NTD w as associated w ith a 71% reduct ion in recurren ce of NTD40) (con firm th at vitam in B12 levels are n orm al) 2. folate an tagon ists (e.g. carbam azepin e) doubles th e in ciden ce of MM 3. m others w ith 5, 10-m ethylenetetrahydrofolate reductase (MTHFR) gene polym orphism . The com - m on variant, C677 T, substitutes an alanine residue for valine at position 222 in the folate depend- ent MTHFR enzym e → decreased enzym e activity → reduced levels of tissue folate, and increased levels of hom ocysteine in th e plasm a. This polym orphism m ay be h om ozygous (TT genotype) or heterozygous (CT genotype); present in ≈10%and 38%of the population, respectively. The e ects w ith the TT genotype are m ore pronounced than w ith th e heterozygous CT form , and there is an in creased risk of neural tube defects, as w ell as a lesser in creased risk of cardiovascular disease41 4. use of valproic acid (Depaken e®) durin g pregn an cy is associated w ith a 1–2%risk of NTD42 5. m atern al h eat exposure in th e form of h ot-t ubs, saun as or fever (but n ot elect ric blan kets) in th e first t rim ester w as associated w ith an in creased risk of NTDs43 6. obesit y (before an d durin g pregn an cy) in creases th e risk of NTD44,45 7. m atern al cocain e abuse m ay in crease th e risk of m icroceph aly, disorders of n euron al m igration , n euron al di eren tiation an d m yelin ation 35 17.2.4 Prenat al det ect ion of neural t ube defect s Serum alpha-fet oprot ein (AFP) See Alph a-fetoprotein (p.600) for backgroun d. A h igh m atern al serum AFP (≥ 2 m ultiples of th e m edian for th e appropriate week of gestation) betw een 15–20 weeks gestation carries a relative risk of 224 for n eural tube defects, an d an abnorm al value (h igh or low ) was associated w ith 34% of all m ajor congen ital defects.46 The sen sitivity of m atern al serum AFP for spina bifida w as 91% (10 of 11 cases), it was 100% for 9 cases of anenceph aly. How ever, oth er series sh ow a lower sensitivity. Closed lum bosacral spine defects, accounting for ≈ 20% of spina bifida patients,47 w ill probably be m issed by serum AFP screen ing, and m ay also be m issed on ultrasound. Since m aternal serum AFP rises during norm al pregnan cy, an overestim ate of gestational age m ay cause an elevated AFP to be in terpreted as n orm al, and an underestim ate m ay cause a norm al level to be interpreted as elevated.48 Ult rasound Pren atal ult rasoun d w ill detect 90–95% of cases of spin a bifida, an d th us in cases of elevated AFP, it can h elp di eren tiate NTDs from n on -n eurologic causes of elevated AFP (e.g. om phalocele), an d can help to m ore accurately estim ate gestational age. Am niocentesis For pregn an cies subsequen t to a MM, if pren atal ultrasoun d does n ot sh ow spin al dysraph ism , th en am n iocen tesis is recom m en ded (even if abort ion is n ot con sidered, it m ay allow for opt im al post- par tum care if MM is diagn osed). Amniotic fluid AFP levels are elevated w ith open n eural tube defect s, w ith a peak betw een w eeks 13–15 of pregn an cy. Am n iocentesis also carr ies a ≈ 6% risk of fetal loss in th is population . 17 17.3 Neurent eric cyst s 17.3.1 General inform at ion No un iform ly accepted n om en clature. Working defin ition : CNS cyst lin ed by en doth elium prim arily resem blin g th at of th e GI t ract , or less often , respirator y tract. Congen ital. Not t rue n eoplasm s. Most com m on altern ate term : en terogen ous cyst. Less com m on term s in clude: teratom atous cyst, in testi- n om a, arch en teric cyst,49 en terogen e cyst, an d en doderm al cyst. Usually a ect th e upper th oracic an d low er cervical spin e.50 Associated developm en tal vertebral an om alies (e.g. diastem atom yelia) are com m on .51 Rarely in tracran ial (see below ). Spin al n euren teric cysts (NEC) m ay h ave a fistulous or fibrous con n ect ion to th e GI tract (th rough a spin al dysraph ism ) an d som e call th ese en doderm al

Prim ary Craniospinal Anom alies 291 sin us cysts. Occurs as a result of persisten ce of th e n euren teric can al (tem porar y duct betw een th e n otoch ord an d th e prim itive gut (am n iotic an d yolk sacs) form ed durin g w eek 3 of em br yogen esis by breakdow n of the floor of the notochordal canal). 17.3.2 Int racranial neurent eric cyst s General inform at ion Rare, m ost com m on in p -fossa. In it ially, m ay be di cult to rule-out m etastasis from an extrem ely w ell-di eren tiated prim ar y aden ocarcin om a of un kn ow n origin (absen ce of progressive disease sug- gests NEC). Locat ion s: 1. posterior fossa a) cerebellopon tin e an gle (CPA)49: usually in t radural, extraaxial (case report of extradural lesion w ith bone destruction52) b) in m idline anterior to brainstem 50 c) cisterna m agna53 2. supraten torial: on ly 15 case reports as of 2004.54 Location s: suprasellar55 (possible con fusion w ith Rath ke’s cleft cyst), fron tal lobe in t raparen chym al,54 quadrigem in al plate region , dural- based extra-axial. Source of en doderm is con troversial sin ce th e prim it ive foregut exten ds cran i- ally on ly to th e m idbrain .56 Th eor y: colloid cysts, Rath ke cleft cysts, an d supraten torial NECs m ay all arise from rem n an ts of Seesel’s pouch , a tran sien t en doderm ally derived divert iculum of th e cran ial en d of th e em br yon ic foregut57 Clin ica l Most com m on ly presen t durin g th e first decade of life.51 Pain or m yelopathy from th e in traspin al m ass are the m ost com m on presentations in older ch ildren an d adults. Neonates and young children m ay present w ith cardiorespirator y com prom ise from an in trathoracic m ass, or w ith cer vical spin al cord com pression .51 Men in gitis m ay occur from th e fistulous tract , especially in n ew born s an d in fan ts. Im aging In tracran ial NEC: ● CT: u su ally low d en sit y, n on en h an cing58 ● T1W I MRI: isoin ten se or sl hyperin ten se to CSF (m ay be hyperin ten se if th ere are blood products). T2W I isoin ten se to CSF.58 Non en h an cing Hist ology Most are sim ple cysts lin ed by cuboidal-colum n ar epith elium an d m ucin secretin g goblet cells. Less com m on t ypes of epith elium described in clude: stratified squam ous an d pseudostratified colum n ar, an d ciliated epith elial cells. Mesoderm al com pon en ts m ay be presen t , in cluding sm ooth m uscle an d adipose tissue, an d som e h ave called th ese teratom atous cysts59,60 w h ich is n ot to be con fused w ith teratom as w h ich are true germ in al cell n eoplasm s. May be h istologically iden tical to colloid cysts. Treat m ent 17 Spinal NEC Surgical rem oval usually reverses th e sym ptom s. Recurren ce is un com m on w ith com plete rem oval of cyst wall. Intracranial NEC Capsule adh eren t to brain stem m ay preven t com plete resection , w h ich predisposes to delayed recur- ren ce. Apparen tly successful treatm en t by evacuation of con ten ts an d m arsupialization h as been reported (5 cases, m ean follow -up: 5 yrs61). In com plete rem oval requires lon g-term follow -up. Hydroceph alus is sh un ted if in dicated.

292 Developm ental Anom alies 17 Re fe r e n ce s Pathogen esis of Posterior Neural Tube Closure Defects. Neurosurger y. 1986; 18:559–564 [1] Carm el PW . Man agem en t of th e Ch iari Malform a- [25] Bell WO, Ch arn ey EB, Bru ce DA, et al. Sym ptom at ic tion s in Ch ild h ood . Clin ical Neurosurg. 1983; Arn old -Ch iari Malform ation : Review of Exp erien ce 30:385–406 w ith 22 Cases. J Neu rosu rg. 1987; 66:812–816 [2] Spillan e JD, Pallis C, Jon es AM. Develop m en tal [26] Brow n lee R, Myles T, Ham ilton MG, An son JA, Ben - Abn orm alities in th e Region of th e Foram en Mag- zel EC, Aw ad IA. In : Th e Ch iari III an d IV m alform a- n u m . Brain . 1957; 80:11–52 tion s. Syrin gom yelia an d th e Ch iari Malform ation s. Park Ridge, IL: Am erican Association of Neurological [3] Pau l KS, Lye RH, Stran g FA, et al. Arn old- Ch iari Mal- Surgeons; 1997:83–90 form ation: Review of 71 Cases. J Neurosurg. 1983; 58:183–187 [27] Raim on d i AJ. Pediatric n eu rorad iology. Ph ilad el- p h ia: W . B. Sau n ders; 1972 [4] Gu in to G, Zam oran o C, Dom in gu ez F, San d oval B, Villasan a O, Ort iz A. Ch iari I m alform ation : Part I. [28] Cast illo M, Qu en cer RM, Dom in gu ez R. Ch iari III Con tem p Neu rosu rg. 2004; 26:1–7 m alform ation : im agin g features. AJNR Am J Neuro- radiol. 1992; 13:107–113 [5] Bah uleyan B, Rao A, Chacko AG, Daniel RT. Supra- cerebellar arachn oid cyst - a rare cause of acquired [29] Ch iari H. Über verän deru n gen d es klein h irn s d es Ch iari I m alform ation . Jou rn al of Clin ical Neu ro- science. 2006; 14:895–898 p on s u n d der m edulla oblon gata in folge von conge- n italer h ydroceph alie des grosshirn s. Den ksch r [6] Sath i S, Stieg PE. \"Acquired\" Ch iari I Malform ation Akad W iss W ien . 1895; 63:71–116 After Mu lt ip le Lu m bar Pun ct u res: Case Repor t. [30] Lem ire RJ. Neural Tu be Defects. JAMA. 1988; Neurosurger y. 1993; 32:306–309 259:558–562 [31] Sut ton LN, Bru ce DA, Sch u t L. Hyd ran en cep h aly ver- [7] Levy W J, Mason L, Hah n JF. Ch iari Malform ation su s Maxim al Hydrocep h alu s: An Im portan t Clin ical Presen tin g in Adults: A Surgical Experien ce in 127 Dist in ct ion . Neu rosu rgery. 1980; 6:35–38 Cases. Neurosurgery. 1983; 12:377–390 [32] Dublin AB, Fren ch BN. Diagn ostic Im age Evaluation of Hydran en ceph aly an d Pictorially Sim ilar En tit ies [8] Bejjan i GK, Cockerh am KP. Adult Chiari m alform a- w ith Em p h asis on Com p uted Tom ograp hy. Rad iolo- t ion . Con tem p Neu rosurg. 2001; 23:1–7 gy. 1980; 137:81–91 [9] Rh oton AL. Microsurger y of Arn old-Chiari Malfor- [33] Matson DD. Neurosurgery of In fan cy an d Child- m ation in Adults w ith and w ith out Hydrom yelia. J Neurosurg. 1976; 45:473–483 h ood. 2n d ed. Sprin gfield: Ch arles C Thom as; 1969 [34] DeMyer W , Zem an W , Palm er CG. Th e Face Predicts [10] Gin gold SI, W in field JA. Oscillopsia an d Prim ary Cerebellar Ectop ie: Case Rep ort an d Review of th e th e Brain : Diagn ostic Sign ifican ce of Median Facial Literatu re. Neu rosu rger y. 1991; 29:932–936 An om alies for Holoprosen ceph aly (Arh in en ce- p h aly). Ped iatrics. 1964; 34:256–263 [11] Aboulezz AO, Sartor K, Geyer CA, Gado MH. Position [35] Volpe JJ. E ect of Cocain e Use on th e Fet us. N En gl J of cerebellar ton sils in th e n orm al population and Med. 1992; 327:399–407 in patien ts w ith Ch iari m alform ation : a qu an titat ive [36] Sect ion of Pediatric Neurosurgery of th e Am erican ap proach w ith MR im agin g. J Com p ut Assist Associat ion of Neu rological Surgeon s. Ped iatric Tom ogr. 1985; 9:1033–1036 Neu rosu rger y. New York 1982 [37] Werler MM, Sh ap iro S, Mitch ell AA. Pericon cept u al [12] Barkovich AJ, W ippold FJ, Sherm an JL, Citrin CM. Folic Acid Exposure an d Risk of Occuren t Neural Sign ifican ce of Cerebellar Ton sillar Posit ion on MR. Tube Defects. JAMA. 1993; 269:1257–1261 AJNR. 1986; 7:795–799 [38] Cen ters for Disease Con t rol. Recom m en dation s for Use of Folic Acid to Red uce Num ber of Sp in a Bifid a [13] Mikulis DJ, Diaz O, Egglin TK, San ch ez R. Varian ce of Cases an d Oth er Neural Tu be Defects. MMW R. th e p osit ion of th e cerebellar ton sils w ith age: p re- 1992; 41:RR–14 lim in ar y report . Rad iology. 1992; 183:725–728 [39] Daly LE, Kirke PN, Molloy A, et al. Folate Levels an d Neu ral Tube Defects. JAMA. 1995; 274:1698–1702 [14] Iskan d ar BJ, Hed lun d GL, Grabb PA, Oakes W J. Th e [40] Wald N, Sn eddon J. Preven tion of n eural t ube resolution of syrin gohydrom yelia w ith out h in d- d efects: Results of th e Medical Research Cou n cil brain h ern iation after posterior fossa decom p res- Vitam in Stu d y. Lan cet. 1991; 338:131–137 sion . J Neurosurg. 1998; 89:212–216 [41] Kirke PN, Mills JL, Molloy AM, Brody LC, O'Lear y VB, Daly L, Mu rray S, Con ley M, Mayn e PD, Sm ith O, [15] Mead ow s J, Kraut M, Guarn ieri M, Harou n RI, Car- Scott JM. Im pact of th e MTHFR C677 T polym or- son BS. Asym ptom atic Ch iari Typ e I m alform ation s p h ism on risk of n eural t ube d efects: case-con trol iden tified on m agn etic resonan ce im aging. J Neuro- st udy. BMJ. 2004; 328:1535–1536 surg. 2000; 92:920–926 [42] Oakesh ott P, Hun t GM. Valp roate an d Sp in a Bifida. Br Med J. 1989; 298:1300–1301 [16] Steven s EA, Powers AK, Sw easey TA, Tatter SB, Oje- [43] Milun sky A, Ulcickas M, Roth m an J, et al. Matern al m an n RG. Sim p lified h ar vest of au tologou s p ericra- Heat Exposure an d Neural Tube Defects. JAMA. nium for du raplast y in Ch iari m alform ation Type I. 1992; 268:882–885 Tech n ical n ote. J Neu rosu rg Sp in e. 2009; 11:80–83 [44] Werler MM, Lou ik C, Sh ap iro S, Mitch ell AA. Pre- pregn an t Weigh t in Relation to Risk of Neu ral Tu be [17] Dyste GN, Men ezes AH, Van Gild er JC. Sym ptom at ic Defects. JAMA. 1996; 275:1089–1092 Ch iari Malform ation s: An An alysis of Presen tation , [45] Sh aw GM, Velie EM, Sch a er D. Risk of Neural Tube Man agem en t , an d Lon g-Term Ou tcom e. J Neu ro- Defect-A ected Pregnan cies Am on g Obese Wom en . surg. 1989; 71:159–168 JAMA. 1996; 275:1093–1096 [18] Peach B. Th e Arn old -Ch iari Malform ation . Morp h o- [46] Milun sky A, Jick SS, Bru ell CL, MacLaugh lin DS, gen esis. Arch Neurol. 1965; 12:527–535 Tsu n g YK, Jick H, Roth m an KJ, W illett W . Predict ive [19] Taveras JM, Pile-Spellm an J. Neurorad iology. 3rd Values, Relative Risks, an d Overall Ben efits of High ed. Balt im ore: W illiam s an d W ilkins; 1996 an d Low Matern al Serum Alph a-Fetoprotein Scree- n in g in Singleton Pregn an cies: New epid em iologic [20] Pollack IF, Pang D, Albrigh t AL, Krieger D. Outcom e data. Am J Obstet Gyn ecol. 1989; 161:291–297 Follow in g Hin dbrain Decom pression of Sym pto- [47] Bu rton BK. Alp h a-Fetop rotein Screen in g. Adv m atic Chiari Malform ation s in Children Previously Pediatr. 1986; 33:181–196 Treated w ith Myelom enin gocele Closure an d [48] Ben n ett MJ, Blau K, Joh n son RD, Ch am berlain GVP. Sh un ts. J Neurosurg. 1992; 77:881–888 Som e Problem s of Alph a-Fetoprotein Screen in g. [21] Park TS, Ho m an HJ, Hen drick EB, et al. Experien ce Lan cet. 1978; 2:1296–1297 w ith Su rgical Decom pression of th e Arn old-Ch iari [49] En yon -Lew is NJ, Kitch en N, Scaravilli F, Brookes GB. Malform ation in Youn g In fan ts w ith Myelom en in- gocele. Neurosurgery. 1983; 13:147–152 Neuren teric Cyst of th e Cerebellop on t in e An gle. Neurosurger y. 1998; 42:655–658 [22] Pollack IF, Pang D, Kocosh is S, Pu t n am P. Neu rogen ic Dysph agia Resultin g from Ch iari Malform ation s. Neurosurger y. 1992; 30:709–719 [23] Ho m an HJ, Hen drick EB, Hum ph reys RP. Man ifes- tations an d Man agem en t of Arn old-Chiari Malfor- m ation in Patien ts w ith Myelom en in gocele. Ch ild s Brain . 1975; 1:255–259 [24] Gilber t JN, Jon es KL, Rorke LB, et al. Cen tral Nervous System An om alies Associated w ith Myelom en ingo- cele, Hydroceph alus, an d th e Arn old-Ch iari Malfor- m ation : Reapp raisal of Th eories Regard ing th e

Prim ary Craniospinal Anom alies 293 [50] Lin J, Feng H, Li F, Ch en Z, W u G. Ven t ral brain stem posterior fossa: recognition , m an agem en t, an d en terogen ous cyst: an un usual location . Acta Neu- em br yogenesis. Neurosurger y. 1991; 29:893–7; dis- roch ir (Wien ). 2004; 146:419–20; discussion 420 cussion 897-8 [51] LeDoux MS, Faye-Petersen OM, Aronin PA. Lum bo- [57] Graziani N, Dufour H, Figarella-Bran ger D, Don n et sacral Neu ren teric Cyst in an In fan t. J Neu rosu rg. A, Bouillot P, Grisoli F. Do th e suprasellar n euren ter- 1993; 78:821–825 ic cyst, th e Rath ke cleft cyst an d th e colloid cyst con stitute a sam e en tit y? Acta Neuroch ir (W ien ). [52] In ou e T, Kawah ara N, Sh ibah ara J, Masum oto T, Usa- 1995; 133:174–180 m i K, Kirin o T. Ext radural n euren teric cyst of th e [58] Sh in JH, Byu n BJ, Kim DW , Ch oi DL. Neu ren teric cyst cerebellop on tin e an gle. Case rep or t . J Neurosurg. in th e cerebellopon tin e angle w ith xan thogranu- 2004; 100:1091–1093 lom atous changes: serial MR fin din gs w ith path o- [53] Boto GR, Lobato RD, Ram os A, Ricoy JR, Alen JF, logic correlation . AJNR Am J Neurorad iol. 2002; Ben ito A. En terogen ous cyst of th e cistern a m agn a. 23:663–665 Acta Neuroch ir (W ien ). 2000; 142:715–716 [54] Ch ristov C, Ch retien F, Bru gieres P, Djin djian M. [59] Morita Y. Neu ren teric Cyst or Teratom atou s Cyst. J Gian t su p raten torial en terogen ou s cyst: rep or t of a Neurosurg. 1994; 80 case, literature review, and discussion of pathogen- esis. Neurosurger y. 2004; 54:759–63; discussion [60] Hes R. Neu ren teric Cyst or Teratom atou s Cyst. J 763 [55] Fan d in o J, Garcia-Abeledo M. [Gian t in traven t ricu lar Neurosurg. 1994; 80:179–180 arachn oid cyst: report of 2 cases]. Rev Neurol. 1998; [61] Goel A. Com m en t on Lin J, et al.: Ven t ral brain stem 26:763–765 en terogen ous cyst: an u n usual location . Acta Neu - [56] Harris CP, Dias MS, Brockm eyer DL, Tow n sen d JJ, rochir (Wien). 2004; 146 Willis BK, Apfelbau m RI. Neu ren teric cysts of th e 17



Part V 18 Com a 296 19 Brain Death and 307 Com a and Brain Deat h Organ Donat ion V

296 Com a and Brain Death 18 Com a 18.1 General inform at ion Con sciousn ess h as t w o com pon en ts: arousal an d con ten t. Im pairm en t of arousal can var y from m ild (drow sin ess or som n olen ce), to obtun dation , to st upor to com a. Com a is th e severest im pairm en t of arousal, and is defined as the inabilit y to obey com m ands, speak, or open th e eyes to pain. Th e Glasgow Com a Scale (GCS) is a w idely used scoring system w ith good repeatabilit y an d is sh ow n in Table 18.1 (n ote: th e scale is used to assess level of con sciousn ess an d is n ot design ed for follow in g n eurologic deficits). Gen eral pract ice is to record a “T” (for “in tubated”) n ext to th e verbal score an d th e total score for patien ts w h ose verbal axis can n ot be assessed because of in tubation .2 No sin gle GCS score defin es a cuto for com a, h ow ever, 90%of patien ts w ith GCS ≤ 8 an d n on e w ith GCS ≥ 9 m eet th e above defin ition of com a. Th us, GCS ≤ 8 is a gen erally accepted operation al defin i- tion of com a. A n um ber of scales for use in ch ildren h ave been proposed. On e is sh ow n in Table 18.2.3 Com a results from on e or m ore of th e follow in g: ● dysfun ct ion of h igh brain stem (cen tral upper pon s) or m idbrain ● bilateral dien ceph alic dysfun ct ion ● di use lesion s in both cerebral h em isph eres (cort ical or subcort ical w h ite m atter) Table 18.1 Glasgow com aa scale1 (recom m ended for age ≥ 4 yrs) Point sb Best eye opening Best verbal Best m ot or 6– – obeys 5– o rie n t e d localizes pain 4 spontaneous confused withdraws to pain 3 to speech in a p p ro p ria t e flexion (decorticate) 2 to painc in co m p re h e n sib le extensor (decerebrate) 1 none none noned atechnically, this is a scale of im paired consciousness, whereas “com a” implies unresponsiveness brange of total points: 3 (worst) to 15 (normal) cwhen testing eye opening to pain, use peripheral stim ulus (the grimace associated with central pain m ay cause eye closure) dif no m otor response, im portant to exclude spinal cord transection Table 18.2 Children’s com a scalea (for age < 4 yrs) Point sb Best eye Best verbal Best m otor obeys 6– – localizes pain 5 – smiles, oriented to sound, follows objects, withdraws to spontaneous in t e ract s pain 18 flexion (decor- Cr yin g Int eract ion t ica t e ) 4 extensor (de- consolable in a p p ro p ria t e cerebrate) none 3 to speech inconsistently consol- m o a n in g 2 to pain a b le re st le ss inconsolable 1 none none none asam e as adult Glasgow com a scale except for verbal response3 brange of total points: 3 (worst) to 15 (normal)

Com a 297 18.2 Post uring 18.2.1 General inform at ion Th e follow in g term s do n ot accurately localize th e site of th e lesion . Decort icate posturin g im plies a m ore rostral lesion th an exten sor posturing, an d progn osis m ay be sligh tly better. 18.2.2 Decort icat e post uring Classically attributed to disin h ibition by rem oval of cort icospin al path w ays above th e m idbrain . Over view : abn orm al flexion in UE an d exten sion in LE. De t a il: ● UE: slow flexion of arm , w rist an d fin gers w ith adduct ion ● LE: exten sion , in tern al rotat ion , plan tarflexion 18.2.3 Decerebrat e post uring Classically att ributed to disin h ibition of vestibulospin al tract (m ore caudal) an d pon tin e reticular form ation (RF) by rem oving in h ibition of m edullar y RF (tran sect ion at in tercollicular level, betw een vestibular an d red n uclei). Over view : abn orm al exten sion in UE an d LE. De t a il: ● Head & trunk: opisth otonos (head and trunk extended), teeth clenched ● UE: arm s exten ded, adducted an d hyperpron ated (in tern ally rotated), w rists flexed, fin gers flexed ● LE: exten ded an d in tern ally rotated, feet plan tarflexed an d inver ted, toes plan tarflexed. 18.3 Et iologies of com a 18.3.1 Toxic/m et abolic causes of com a 1. elect rolyte im balan ce: especially hypo- or hypern atrem ia, hypercalcem ia, ren al failure w ith ele- vated BUN & creatin in e, liver failure w ith elevated am m on ia 2. en docrin e: hypoglycem ia, n on ketotic hyperosm olar state, DKA (diabetic ketoacidosis, AKA dia- betic com a), m yxedem a com a, Addison ian crisis (hypoadren alism ) 3. vascular: vasculit is, DIC, hyper tensive en ceph alopathy (p. 194) 4. toxic: EtOH, drug overdose (in cludin g n arcotics, iatrogen ic polyph arm acy, barbiturates), lead in toxication , carbon m on oxide (CO) poison in g, cyclosporin e (causes an en ceph alopathy th at sh ow s w h ite-m atter ch anges on MRI th at is often reversible w ith discon tin uation of th e drug) 5. in fect ious/in flam m ator y: m en in gitis, en ceph alitis, sepsis, lupus cerebritis, n eurosarcoidosis (p.189), toxic-shock syn drom e 6. neoplastic: leptom eningeal carcinom atosis, rupture of neoplastic cyst 7. n utrition al: Wern icke’s en ceph alopathy, vitam in B12 deficien cy 8. in herited m etabolic disorders: porphyria, lact ic acidosis 9. organ failure: urem ia, hypoxem ia, h epatic en ceph alopathy, Reye’s syn drom e, an oxic en ceph al- opathy (e.g. post-resuscitation from cardiac arrest), CO2 n arcosis 10. epilept ic: status epilepticus (in cludin g n on -convulsive status), post-ictal state (especially w ith unobserved seizure) 18.3.2 St ruct ural causes of com a 18 1. vascular: a) bilateral cort ical or subcort ical in farcts (e.g. w ith cardioem bolism due to SBE, m it ral sten osis, A-fib, m ural th rom bus…) b) occlusion of vessel supplyin g both cerebral h em ispheres (e.g. severe bilateral carotid sten osis) c) bilateral dien ceph alic in farcts: w ell described syn drom e. May be due to occlusion of a th ala- m o-perforator supplying both m edial th alam ic areas or w ith “top -of-th e-basilar” occlusion . In itially resem bles m etabolic com a (in cludin g di use slow in g on EEG), patien t even tually arouses w ith apathy, m em ory loss, vertical gaze paresis 2. in fect ious: abscess w ith sign ifican t m ass e ect , subdural em pyem a, h erpes sim plex en ceph alit is 3. traum a: hem orrhagic contusions, edem a, hem atom a (see below ) 4. n eoplastic: prim ary or m etastatic

298 Com a and Brain Death 5. h ern iation from m ass e ect: presum ably brain stem com pression causes dysfun ct ion of reticular activatin g system or m ass in on e h em isph ere causin g com pression of th e oth er results in bilateral h em isph ere dysfun ct ion 6. in creased in tracran ial pressure: reduces CBF 7. acute lateral sh ift (m idlin e sh ift) of th e brain : e.g. due h em atom a (subdural or epidural) Table 18.3) 18.3.3 Pseudocom a Di eren tial diagn osis: 1. locked-in syn drom e: ven tral pon tin e in farction 2. psych iatric: cataton ia, conversion react ion 3. n eurom uscular w eakn ess: m yasth en ia gravis, Guillain -Barré 18.3.4 Approach t o t he com at ose pat ient General inform at ion Th is sect ion addresses n on traum atic com a. See Head t raum a (p. 824) for th at topic. In itial evaluation : in cludes m easures to protect brain (by providin g CBF, O2, an d glucose), assesses upper brain stem (Cr. N. VIII), an d rapidly iden tifies surgical em ergen cies. Keep “pseudocom a” as a possible etiology in back of m ind. Out line of approach t o com at ose pat ient 1. cardiovascular stabilization : establish airw ay, ch eck circulation (h eartbeat, BP, carotid pulse), CPR if n ecessar y 2. obtain blood for tests a) STAT: elect rolytes (especially Na, glucose, BUN), CBC+ di , ABG b) oth ers as appropriate: toxicology screen (serum & urin e), calcium , am m on ia, an tiepileptic drug (AED) levels (if patien t is takin g AEDs) 3. adm in ister em ergency supportive m edication s a) glucose: at least 25 m l of D50 IVP. Due to poten tially h arm ful e ect of glucose in global isch e- m ia, if possible ch eck fin gerstick glucose first, oth erw ise glucose is given w ith out exception , unless it is know n w ith certaint y that serum glucose is n orm al b) n aloxon e (Narcan®): in case of n arcotic overdose. 1 am p (0.4 m g) IVP c) flum azen il (Rom azicon ®): in case of ben zodiazepin e overdose. Start w ith 0.2 m g IV over 30 secon ds, w ait 30 secs, th en give 0.3 m g over 30 secs at 1 m in ute in ter vals up to 3 m g or until patient arouses d) th iam in e: 50–100 m g IVP (3%of Wern icke’s presen t w ith com a) 4. core neuro exam (assesses m idbrain /upper pons, allow s em ergency m easures to be instituted rapidly, m ore th orough evaluation possible on ce stabilized): see Core n euro exam below 5. if h ern iation syn drom e or sign s of expan ding p -fossa lesion w ith brain stem com pression Table 18.4): in itiate m easures to low er ICP – see Treatm en t m easures for elevated ICP (p.866) -, th en get a CT scan if pat ien t begin s im proving, oth erw ise em ergen cy surger y. Do NOT do LP 6. if m en ingitis suspected (altered m en tal status + fever, m en in geal sign s…) a) if n o in dication of h ern iation , p -fossa m ass ( Table 18.4), focal deficit in dicat in g m ass e ect or papilledem a: perform LP, start an tibiotics im m ediately (do n ot w ait for CSF results); see Meningitis (p.318) 1 8 b) if evidence of possible m ass e ect, coagulopathy or h ern iation , CT to R/O m ass. If sign ifican t delay an ticipated, con sider em piric an tibiotics or careful LP w ith sm all gauge n eedle (≤ 22 Table 18.3 E ect of lateral shift on level of consciousness4 Am ount of m idline shift Level of consciousness 0–3 mm alert 3–4 mm drowsy 6–8.5 mm st u p o ro u s 8–13 mm com at ose http://e-surg.com