Handbook of Neurosurgery 8th Edition-4

Neurovascular Disorders and Neurotoxicology 199 11.3.4 Ot her vasculit ides Periart erit is nodosa AKA polyarterit is n odosa. Actually a group of n ecrotizin g vasculit ides, in cluding: ● classic periarteritis n odosa (PAN): a m ultisystem disease w ith in flam m atory n ecrosis, th rom bosis (occlusion ), an d h em orrh age of arteries an d arterioles in ever y organ except lun g & spleen . Nod- ules m ay be palpated alon g m edium sized m uscular arteries. Com m on ly produces m on on euritis m ultiplex, w eigh t loss, fever, an d tachycardia. Periph eral n er ve m an ifestation s are att ributed to arteritic occlusion of vasa n er vorum . CNS m an ifestation s are un com m on an d in clude H/A, seiz- ures, SAH, retin al h em orrh ages, an d stroke in ≈ 13% ● allergic an giitis an d gran ulom atosis (Ch urg-Strauss syn drom e) ● system ic necrotizing vasculitis Th ese pat ien ts do better w h en treated w ith cycloph osph am ide rath er th an steroids. Wegener’s granulom at osis 11 General inform ation A system ic necrotizing granulom atous vasculitis involving the respirator y tract (lun g → cough/h e- m optysis, an d/or n asal airw ays → serosanguin ous n asal drain age ± septal perforation→ ch aracteristic “saddle n ose deform it y”) an d frequen tly th e kidn eys (n o reported cases of kidn ey involvem en t w ith - out resp irator y).29 Nasal obstruct ion an d crustin g are th e usual in itial fin dings. Ar th ralgia (n ot true ar th rit is) is presen t in > 50%. Neurologic involvem en t usually con sists of cran ial n er ve dysfun ct ion (usually II, III, IV, & VI; less often V, VII, & VIII; an d least com m on ly IX, X, XI, & XII) an d periph eral n europath ies, w ith diabetes in sipidus (occasion ally preceding oth er sym ptom s by up to 9 m on th s). Focal lesion s of th e brain an d spinal cord occur less frequen tly. Di erential diagnosis Di eren tial diagn osis in cludes: ● “leth al m idlin e gran ulom a” (m ay be sim ilar or iden tical to polym orph ic reticulosis) m ay evolve in to lym ph om a. May cause fulm in an t local destruction of th e n asal tissue. Di eren tiation is crucial as th is con dition is treated by radiation ; on e sh ould avoid im m un e suppression (e.g. cycloph os- ph am ide). Probably does n ot involve true gran ulom as. Ren al an d trach eal involvem en t do n ot occur ● fun gal disease: Sporoth rix sch en ckii & Coccidioides m ay cause iden tical syn drom e ● oth er vasculitides: especially Ch urg-St rauss syn drom e (asth m a an d periph eral eosin oph ilia usu- ally seen ), an d PAN (gran ulom as usually lackin g) Evaluat ion Biopsy of upper airw ays con sists of rem ovin g all crusts, an d obtain ing as m uch friable m ucosa as possible. Th is tissue sh ould be fixed in form aldehyde an d exam in ed path ologically w ith in 24 h rs (do n ot freeze). A sam ple sh ould also be cultured (in cluding fun gal an d acid-fast cultures). Ren al biopsy sh ould n ot be don e w h en m ore specific t issue is available from th e upper airw ay. Treatm ent Un t reated, Wegen er’s gran ulom atosis is rapidly fatal, w ith a m edian sur vival of 5 m on th s, an d m ore th an 90%of patien ts are dead w ith in 2 years of diagn osis.30 For fulm in at in g disease: predn ison e 60– 80 m g/d un til disease is con trolled (docum en ted by decreasing ESR an d im provem en t of serum creatin ine). W h en disease is stable: cycloph osph am ide (Cytoxan ®) ≈ 2 m g/kg daily (takes 2–3 w eeks to h ave an e ect ). Con tin ue 1 year beyon d last eviden ce of active disease. Low -dose w eekly m eth otrexate m ay be an acceptable altern ative to cycloph osph am ide in selected patien ts.30 11.3.5 Lym phom at oid granulom at osis Rare; a ect s m ain ly th e lun gs, skin (er yth em atous m acules or in durated plaques in 40%) an d n er v- ous system (CNS in 20%, periph eral n europath ies in 15%). Sin uses, lym ph n odes, an d spleen are usu- ally spared.

200 General and Neurology 11.3.6 Behçet ’s syndrom e Relapsin g ocular lesion s an d recurren t oral an d gen ital ulcers, w ith occasion al skin lesion s, th rom bo- ph lebitis, an d arth rit is.10 H/A occur in > 50%. Neurologic involvem en t in cludes pseudot um or, cerebel- lar ataxia, paraplegia, seizures, an d dural sin us th rom bosis. On ly 5% h ave n eurologic sym ptom s as the presenting com plain t. 86% h ave CSF pleocytosis an d protein elevation . Cerebral an giography is usually n orm al. CT m ay sh ow focal areas of en h ancin g low den sit y. Steroids usually am eliorate ocular and cerebral sym ptom s, but usually have no e ect on skin and gen- ital lesions. Uncontrolled trials of cytotoxic agents → som e benefit. Thalidom ide m ay be e ective (uncon- trolled studies), but carries risk of serious adverse e ects (teratogenicity, peripheral neuropathy…).31 Although painful, the disease is usually benign. Neurologic involvem ent portends a worse prognosis. 11.3.7 Isolat ed CNS vasculit is General inform at ion AKA isolated an giitis of th e CNS. Rare (≈ 20 cases reported32 as of 1983); lim ited to vessels of CNS. Sm all vessel vasculitis is ≈ always presen t → segm en tal in flam m ation an d n ecrosis of sm all leptom e- n in geal an d paren chym al blood vessels w ith surroun ding tissue isch em ia or h em orrh age.10 Present at ion Com bin ation s of H/A, con fusion , dem en tia, an d leth argy. Occasion ally seizures. Focal an d m ultifocal brain disturban ce occurs in > 80%. Visual sym ptom s are frequen t (secon dar y eith er to involvem en t of choroidal an d retinal arteries, or to involvem ent of visual cortex → visual hallucinations). Evaluat ion ESR & W BC count are usually n orm al. CSF m ay be n orm al or h ave pleocytosis an d/or elevated pro- 1 1 tein . CT m ay sh ow en h an cin g areas of low den sit y. An giography (required for diagn osis): ch aracterist ically sh ow s m ultiple areas of sym m etrical n ar- row in g (“strin g of pearls” con figuration ). If n orm al, it does n ot exclude diagn osis. Histological diagnosis (recom m en ded): all biopsy m aterial sh ould be cultured. Brain paren chym a biopsy in frequen tly sh ow s vasculit is. Leptom en ingeal biopsy invariably sh ow s involvem en t. Treat m ent and out com e Reportedly fatal if un t reated, but m ay sm older for years. Rarit y of th is con dition m akes t reatm en t un certain . Recom m en ded: cycloph osph am ide (Cytox- an ®) 2 m g/kg/d an d predn ison e 1 m g/kg/d qod th erapy. NB: th is con dition is th ough t to be T-cell m ediated, but predn ison e causes m ore B-cell suppres- sion , th erefore breakth rough durin g predn ison e th erapy is n ot un com m on . 11.3.8 Hypersensit ivit y vasculit is Neurologic involvem en t is n ot a prom in en t feature of th is group of vasculitides, w h ich in clude: ● drug in duced allergic vasculitis: A n um ber of drugs are associated w ith th e developm en t of cere- bral vasculitis. Th ese in clude m eth am ph etam in es (“speed”), cocain e (fran k vasculitis occurs33 but is rare), heroin and eph edrine ● cutaneous vasculitis ● serum sickn ess: m ay → en ceph alopathy, seizures, com a, periph eral n europathy an d brach ial p le xo p a t h y ● Hen och -Sch ön lein purp ura 11.3.9 Fibrom uscular dysplasia General inform at ion A vasculopathy (an giopathy) a ect in g prim arily bran ch es of th e aorta, w ith ren al artery involvem en t in 85% of cases (th e m ost com m on site) an d com m on ly associated w ith hyper ten sion . Th e disease h as an in ciden ce of ≈ 1%, an d results in m ult ifocal arterial con striction s an d in terven in g region s of aneurysm al dilatation. Th e secon d m ost com m on ly involved site is th e cer vical in tern al carot id (prim arily n ear C1–2), w ith fibrom uscular dysplasia (FMD) appearin g on 1%of carotid an giogram s, m akin g FMD th e secon d

Neurovascular Disorders and Neurotoxicology 201 m ost com m on cause of extracran ial carotid sten osis.34 Bilateral cer vical ICA involvem en t occurs in ≈ 11 80%of cases. 50%of patien ts w ith carotid FMD h ave renal FMD. Pat ien ts w ith FMD h ave an in creased risk of in t racran ial an eur ysm s an d n eoplasm s, an d are probably at h igh er risk of carotid dissect ion . An eur ysm s an d fibrom uscular dysplasia: Th e reported in ciden ce of an eur ysm s w ith FMD35 ran ges from 20–50%. Et iology Th e actual etiology rem ain s un kn ow n , alth ough congen ital defect s of th e m edia (m uscular layer) and internal elastic layer of the arteries has been iden tified w hich m ay predispose the arteries to injur y from oth erw ise w ell-tolerated t raum a. A h igh fam ilial rate of st rokes, HTN, an d m igrain e h ave supported th e suggestion th at FMD is an autosom al dom in an t trait w ith reduced pen etran ce in m ales.36 Present at ion Most patien ts h ave recurren t, m ultiple sym ptom s sh ow n in Table 11.4. Up to 50%of pat ien ts present w ith episodes of t ran sien t cerebral isch em ia or in farct ion . How ever, FMD m ay also be an in ciden tal fin din g an d som e cases h ave been follow ed for 5 years w ith out recur- ren ce of isch em ic sym ptom s suggestin g th at FMD m ay be a relatively ben ign con dition . Headach es are com m on ly un ilateral an d m ay be m istaken for t ypical m igrain e. Syn cope m ay be caused by involvem en t of the carotid sinus. Horn er’s syn drom e occurs in ≈ 8% of cases. T-wave ch anges on EKG m ay be seen in up to on e– third of cases, an d m ay be due to involvem en t of the coronary arteries. Dia g n o s is Th e “gold-stan dard” for th e diagn osis of FMD is th e an giogram . Th e th ree an giograph ic t ypes of FMD37 are sh ow n in Table 11.5. Treat m ent Medical th erapy in cludin g an t iplatelet m edication (e.g. aspirin ) h as been recom m en ded. Direct surgical treatm en t is problem ridden due to th e di cult location (h igh carotid arter y, n ear th e base of th e sku ll), an d th e friable n ature of th e vessels m akin g an astam osis or arteriotom y clo- sure di cult. Tran slum in al an gioplast y h as ach ieved som e degree of success. Carotid cavern ous fistulas an d arterial rupture h ave been reported as com plication s. Table 11.4 Previous sym ptoms in 37 cases of aortocranial FMD36 % Sym pt om 78% H/ A 48% m ental distress 38% t in n it u s 34% ve rt ig o 31% cardiac arrhythm ia 31% TIA 31% syncope 21% ca ro t id yn ia 15% epilepsy 12% hearing im pairm ent 8% abdominal angina 8% angina/ MI

202 General and Neurology Table 11.5 Angiographic classification of FMD Typ e Fin d in g s 1 m ost comm on (80–100% of reported cases). Multiple, irregularly spaced, concentric narrowings with normal or dilated intervening segm ents giving rise to the so-called “string of pearls” appearance. Corresponds with arterial m edial fibroplasia 2 focal tubular stenosis, seen in ≈ 7%of cases. Less characteristic for FMD than Type 1, and may also be seen in Takayasu’s arteritis and other conditions 3 “at ypical FMD.” Rare. May take on various appearances, m ost comm only consisting of diverticular outpouchings of one wall of the artery 11.3.10 Miscellaneous vasculopat hies CADASIL Key concept s ● clinical: migraines, dem entia, TIAs, psychiatric disturbances ● MRI: white mat ter abnormalities ● autosomal dom inant inheritance ● anticoagulants controversial, generally discouraged An acronym for Cerebral Autosom al Dom in an t Arteriopathy w ith Subcort ical In farcts an d Leukoen - ceph alopathy.38 A fam ilial disease w ith on set in early adulth ood (m ean age at on set: 45 ± 11 yrs), 1 1 m apped to ch rom osom e 19. Clin ical an d n euroradiologic features are sim ilar to th ose seen w ith m ul- t iple subcor tical in farcts from HTN, except th ere is n o evidence of HTN. Th e vasculopathy is dist in ct from th at seen in lipohyalin osis, arteriosclerosis an d am yloid an giopathy, an d causes th icken in g of th e m edia (by eosin oph ilic, gran ular m aterial) of leptom en in geal an d perforatin g arteries m easurin g 100–400 m cm in diam eter. Clinical involvem ent Recurren t subcor tical in farcts (84%), progressive or stepw ise dem en tia (31%), m igrain e w ith aura (22%), an d depression (20%). All sym ptom at ic an d 18%of asym ptom at ic patien ts h ad prom in en t sub- cort ical w h ite-m atter an d basal ganglia hyperin tensit ies on T2W I MRI. Treatm ent Warfarin (Coum adin ®) is used by som e. 11.3.11 Paraneoplast ic syndrom es a ect ing t he nervous syst em General inform at ion Paraneoplast ic syn drom es (PNS), AKA “rem ote e ect s of can cer.” Develop acutely or subacutely. May m im ic or be m im icked by m etastatic disease. Th e n eurologic disabilit y is usually severe, an d m ay precede oth er m an ifestation s of th e can cer by 6–12 m os. Often on e part icular n eural cell t ype is pre- dom in an tly a ected. Th e presen ce of a PNS m ay porten d a m ore ben ign course of th e can cer. 16%of patien ts w ith lun g Ca, an d 4%w ith breast Ca w ill develop a PNS. Path ogen esis un kn ow n . Th eories: ? toxin ; ? com petition for essen tial subst rate; ? opportun istic in fect ion ; ? auto-im m un e process. Types of syndrom es 1. a ect ing cerebrum or cerebellum a) en cephalitis ● di use ● lim bic an d brain stem : usually due to sm all-cell lun g Ca or test icular Ca39 as a result of serum antineuronal antibodies

Neurovascular Disorders and Neurotoxicology 203 b) “lim bic en ceph alit is” (m esial): dem en tia (decreased m em or y, psych iatric sym ptom s, 11 hallucin ation s) c) pan -cerebellar degen eration (PCD) AKA subacute cerebellar degen eration *: (see below ) d) opsoclon us-m yoclon us syn drom e*: in peds, usually in dicates n euroblastom a 2. a ect ing spin al cord a) poliom yelitis (an terior h orn syn drom e): m im ics ALS (w eakn ess, hyporeflexia, fasciculation s) b) subacute n ecrotizing (transverse) m yelitis: rapid necrosis of spinal cord c) ganglion itis* (dorsal root gan glion): chronic or subacute. Pure sen sory neuronopathy (n ot neuropathy) 3. a ecting peripheral nervous system a) ch ronic sen sor y-m otor: t ypical n europathy (as in DM or EtOH abuse) b) pure sensory (p.1268) 40 c) pure m otor: rare. Alm ost alw ays due to lym ph om a (m ostly Hodgkin’s) d) acute in flam m ator y dem yelin atin g polyradiculopathy, AKA Guillain -Barré (p. 184) e) Eaton -Lam bert (EL) m yasth en ic syn drom e*: rare. 66%of patien ts w ith th is syn drom e w ill h ave can cer, m ost com m on prim ar y is oat cell Ca of lun g. Pre-syn apt ic n eurom uscular jun c- tion (PSNMJ) blockade due to an tibodies again st th e PSNMJ; NB: t rue m yasth en ia gravis (MG) is a post-syn aptic block. Worse in AM, im proves durin g day w ith recruit m en t (opposite of MG, w h ich is w orse at n igh t or w ith exercise due to depletion ). Mostly m otor, but often accom pan ied by paresth esias. MG is a ects m ostly n icot in ic receptors, but EL also a ect s m uscarin ic receptors, an d th erefore auton om ic sym ptom s m ay occur: dr y m outh , m ales m ay h ave im poten ce. Repetitive n er ve st im ulat ion on EMG: for MG use 2–5 Hz st im ulation , for EL use > 10 Hz, MG: decrem en tal respon se w ith low frequen cy, w ith EL th ere is in crem en tal res- ponse (m ore response w ith repeat stim ulation). f) m yasth en ia gravis g) polym yositis: in age > 60 yrs, 25%of pat ien ts w ith th is h ave a m align an cy*, m ost often lin ked to bron ch ogen ic Ca h ) t ype IIb m uscle fiber atrophy: th e m ost com m on paran eoplastic syn drom e; m ain ly proxim al m uscle w eakn ess (sam e as in oth er en docrin e m yopath ies, e.g. hypothyroid, steroid) * “classic” n eurologic PNS. In a patien t w ith out previous can cer h istory presen ting w ith on e of th ese syn drom es w ith an asterisk, w ork-up for occult m align an cy h as h igh yield. Pan-cerebellar degenerat ion Severe Purkinje cell loss (due to an ti-Purkinje cell an tibody) → severe pan -cerebellar dysfun ct ion . Presen ts w ith vert igo, gait an d upper an d low er extrem it y ataxia, dysarth ria, N/V, diplopia, oscillop - sia, nystagm us, oculom otor dysm etria. Usually n ot t reatable n or rem itting even w ith im m un e sup - pression . 20% of patien ts im prove w ith treatm en t of th e prim ary can cer. CT is W NL early, late → cerebellar atrophy. In 70%of cases, cerebellar fin din gs precede diagn osis of can cer. Th e m ost com m on prim ar y m align an cies in pan -cerebellar degen eration are sh ow n in Table 11.6. Evaluat ion ● LP: CSF for cell coun t, cytology an d IgG. Typically W BCs an d IgG are elevated ● Evaluation for prim ar y ○ CT of ch est/abdom en /pelvis ○ lym ph node exam ○ pelvic exam and m am m ogram in w om en Table 11.6 Comm on prim aries with pan-cerebellar degeneration Me n Wom e n lung Ca Hodgkin’s lym phoma ovarian Ca breast uterus Hodgkin’s lymphom a

204 General and Neurology 11.4 Neurot oxicology 11.4.1 Et hanol General inform at ion Th e acute an d ch ron ic e ects of ethyl alcoh ol (eth an ol, EtOH) abuse on th e n er vous system (n ot to m en tion th e e ects of EtOH on oth er organ system s) are protean ,41 an d are beyon d th e scope of th is text). Neurom uscular e ects include: 1. acute in toxication: see below 2. e ects of chronic alcohol abuse a) Wern icke’s en cep h alop at hy (p.206) b) cerebellar degeneration: due to degeneration of Purkinje cells in the cerebellar cortex, pre- dom in an tly in th e an terior superior verm is c) central pontine m yelinolysis (p.115) d) stroke: increased risk of ● in tracerebral hem orrhage (p.1330) ● isch em ic stroke42 ● possibly an eur ysm al SAH e) peripheral neuropathy (p.541) f) skeletal m yopathy 3. e ect s of alcoh ol w ith draw al: usually seen in h abituated drin kers w ith cessation or reduct ion of ethanol intake a) alcoh ol w ith draw al syn drom es: see below b) seizures: up to 33%of patien ts h ave a gen eralized ton ic-clon ic seizure 7–30 h rs after cessation of drin kin g – Alcoh ol w ith draw al seizures (p. 464) c) delirium trem en s (DTs): see below Acut e int oxicat ion 1 1 Th e p rim ar y e ect of Et OH on th e CNS is d ep ression of n eu ron al excit abilit y, im p u lse con d u c- t ion , an d n eu rot ran sm it ter release d u e to d irect e ect s on t h e cell m em bran es. Table 11.7 sh ow s t h e clin ical e ect s associated w it h sp ecific Et OH con cen t rat ion s. Mellan by e ect : t h e severit y of int oxicat ion is greater at any given level w h en blood alcoh ol levels are rising t han w h en fallin g. In m ost jurisdiction s, in dividuals w ith blood eth an ol levels ≥ 21.7 m m ol/l (100 m g/dl) are defin ed as legally in toxicated, and a num ber of states h ave changed this to 80 m g/dl. How ever, even levels of 10.2 m m ol/l (47 m g/dl) are associated w ith in creased risk of involvem en t in m otor veh icle accidents. Ch ron ic alcoh olism leads to in creased toleran ce; in h abituated in dividuals sur vival w ith levels exceeding 1000 m g/dl has been reported. Alcohol w it hdraw al syndrom e General inform ation Com pen sation for th e CNS depressan t e ects of EtOH occurs in ch ron ic alcoh olism . Con sequen tly, reboun d CNS hyperact ivit y m ay result from falling EtOH levels. Clin ical sign s of EtOH w ith draw al are classified as m ajor or m in or (th e degree of auton om ic hyperact ivity an d th e presen ce/absen ce of DTs di eren tiates th ese), as w ell as early (24–48 h rs) or late (> 48 h rs). Sign s/sym ptom s in clude: t rem ulousn ess, hyperreflexia, in som n ia, N/V, auton om ic hyperact ivity (tachycardia, systolic HTN), agitat ion , m yalgias, m ild con fusion . If EtOH w ith draw al seizures (p. 464) occur, th ey ten d to be early. Percept ual dist urban ces or fran k h allucin osis m ay also occur early. Table 11.7 Blood ethanol concentrations [blood EtOH] Clinical effect m m ol/lit er m g/dl 5.4 25 m ild intoxication: altered m ood, im paired cognition, incoordination > 21.7 100 vestibular and cerebellar dysfunction: increased nystagmus, diplopia, dysarthria, ataxia > 108.5 500 usually fatal from respiratory depression

Neurovascular Disorders and Neurotoxicology 205 Hallucin osis con sists of visual an d/or auditor y h allucin ation s w ith an oth erw ise clear sen sorium (w h ich dist in guish es th is from th e h allucin ation s of DTs). DTs can occur 3–4 days after cessation of drinking (see below ). Suppressed by ben zodiazepin es, resum ption of drin kin g, β-adren ergic an tagon ists, or α 2- agon ists. Prevention of and treatm ent for alcohol withdrawal syndrom e 11 See referen ce.43 Mild EtOH w ith draw al is m an aged w ith a quiet, support ive environ m en t, reorien tation an d on e- to-on e con tact. If sym ptom s progress, in stit ute ph arm acologic t reatm en t. Ben zod iazep in es Ben zodiazepin es (BDZs) are th e m ain stay of t reatm en t. Th ey reduce autonom ic hyperact ivity, an d m ay preven t seizures an d/or DTs. All BDZs are e ect ive. In itial doses are sh ow n in Table 11.8 an d are h igh er th an th ose used for t reating an xiet y. Sym ptom triggered dosin g w ith repeated evaluation utilizing a stan dardized protocol (e.g. CIW A-Ar44) m ay be m ore e cacious th an fixed-dose sch ed- ules.45 Avoid IM adm in istration (erratic absorption ). Adju n ct ive m ed icat ion s Associated con dition s com m on ly seen in patien ts experien cin g alcoh ol w ith draw al syn drom e in clude dehydration , fluid an d electrolyte dist urban ces, in fect ion , pan creatitis, an d alcoh olic ketoaci- dosis, an d sh ould be treated accordingly. Oth er m edicat ion s used for EtOH w ith draw al itself in clude: 1. drugs useful for con trolling HTN (caut ion : th ese agen ts sh ould n ot be used alon e because th ey do not prevent progression to m ore severe levels of w ith draw al, and th ey m ay m ask sym ptom s of w ithdrawal) a) β-blockers: also treat m ost associated ta chya r rhythmia s ● a tenolol (Ten orm in ®): reduces len gth of w ith draw al an d BDZ requirem en t ● avoid propranolol (psychotoxic reactions) b) α -agonists: do not use together w ith β-blockers 2. ph en obarbital: an altern ative to BDZs. Long acting, an d h elps prophylax again st seizures 3. baclofen : a sm all study47 foun d 10 m g PO q d X 30 days resulted in rapid reduct ion of sym ptom s after th e in it ial dose an d con tin ued abstin en ce 4. “support ive” m edicat ion s a) thia mine : 100 m g IM q d × 3 d (can be given IV if n eeded, but th ere is risk of adverse react ion ). Ration ale: h igh -con centration glucose m ay precipitate acute Wern icke’s en ceph alopath y in patients w ith thiam ine deficien cy b) folate 1 m g IM, IV or PO q d × 3 d c) MgSO4 1 gm × 1 on adm ission : h elpful on ly if m agn esium levels are low, reduces seizure risk. Be sure ren al fun ct ion is n orm al before adm in isterin g d) vitam in B12 for m acrocyt ic an em ia: 100 m cg IM (do n ot give before folate) e) m ultivitam ins: of ben efit on ly if patien t is m alnourish ed Table 11.8 Guidelines for BDZ doses for EtOH withdrawala Dr u g Do se Oral IV chlordiazepoxide 100 m g initially, then 25–50 mg PO TID-QID, gradually taper over ≈ – (Librium ®) 4 days). Additional doses m ay be needed for continuing agitation, up to 50 mg PO hourly46 lorazepam (Ativan®) 4 mg initially, then 1–2 mg PO q 4 hrs 1–2 mg q 1–2 hrs diazepam 20 mg PO initially, then 10 m g PO BID-QID 5–10 mg (Valium ®) in it ia lly m idazolam titrate drip to (Versed®) desired effect amodify as appropriate based on patient response

206 General and Neurology 5. seizures: see in dication s for treatm en t (p.464) a) p h en yt oin (Dilan tin ®) (p. 446): load w ith 18 m g/kg = 1200 m g/70 kg b) con tin ued seizures m ay som et im es be e ect ively t reated w ith pa ra ldehyde if available 6. eth an ol drip: n ot w idely used. 5%EtOH in D5 W , star t at 20 cc/h r, an d t it rate to a blood level of 100–150 m g/dl Delirium t rem ens (DTs) W h en DTs occur, th ey usually begin w ith in 4 days of th e on set of EtOH w ith draw al, an d t ypically persist for 1–3 days. Sign s an d sym ptom s in clude: profoun d disorien tation , agitation , trem or, in som n ia, h allucin ation s, severe auton om ic in stabilit y (tachycardia, HTN, diaph oresis, hyperth erm ia).48 Mortalit y is 5–10% (h igh er in elderly), but can be reduced w ith treat m en t (in cludin g t reating associated m edical prob- lem s an d treat m en t for seizures). Haloperidol an d ph en oth iazin es m ay con trol h allucin ation s, but can low er th e seizure th resh old. HTN an d tachyarrhyth m ias sh ould be t reated as outlin e above un der alcoh ol w ithdraw al syn drom e. Wernicke’s encephalopathy (WE) General inform ation AKA Wern icke-Korsako en ceph alopath y (n ot to be con fused w ith Korsako ’s syn drom e or Korsak- o ’s psych osis). Classic triad: en cephalopathy (con sistin g of global con fusion ), oph th alm oplegia, an d ataxia (NB: all 3 are present in on ly 10–33%of cases). Due to th iam in e deficien cy. Body stores of th iam in e are adequate on ly for up to ≈ 18 days. May be seen in : 1. a cer tain susceptible subset of th iam in e deficien t alcoh olics. Th iam in e deficien cy h ere is due to a com bin ation of in adequate in take, reduced absorption , decreased h epatic storage, an d im paired u t iliza t io n 2. hyperem esis (as in som e pregnancies) 1 1 3. starvation : in cludin g an orexia n ervosa, rapid w eigh t loss 4. gast roplication (bariatric surger y) 5. h em odialysis 6. cancers 7. AIDS 8. prolonged IV hyperalim en tat ion Clin ica l Oculom otor abn orm alit ies occur in 96%an d in clude: nystagm us (h orizon tal > vert ical), lateral rectus palsy, conjugate-gaze palsies. Gait ataxia is seen in 87%, an d results from a com bin ation of polyn europathy, cerebellar dysfun c- tion , an d vestibular im pairm ent. System ic sym ptom s m ay in clude: vom iting, fever. Diagnostic testing MRI: May show high signal in T2WI and FLAIR im ages in the paraventricular (m edial) thalam us, the floor of the 4th ventricle, and periaqueductal gray of the m idbrain. These changes m ay resolve w ith treat- m ent.49 Atrophy of the m am m illary bodies m ay also be seen. Norm al MRI does not R/O the diagnosis. Treatm ent Wern icke’s en ceph alopathy (WE) is a m edical em ergency. W h en W E is suspected, 100 m g th iam in e sh ould be given IM or IV (oral route is un reliable, see above) daily for 5 days. IV glucose can precip - itate acute W E in th iam in e deficien t patien ts, give th iam in e before glucose. Th iam in e adm in istration im proves eye fin din gs w ith in h ours to days; ataxia an d con fusion im prove in days to w eeks. Many patien ts th at survive are left w ith h orizon tal nystagm us, ataxia, an d 80%h ave Korsako ’s syn drom e (AKA Korsako ’s psych osis), a disabling m em or y dist urban ce involv- in g retrograde an d an terograde am n esia. 11.4.2 Opioids In cludes h eroin (w h ich is usually injected IV, but th e pow der can be sn orted or sm oked) as w ell as prescription drugs. Opioids produce sm all pupils (m iosis).

Neurovascular Disorders and Neurotoxicology 207 Overdose m ay produce: 1. respiratory depression 2. pulm onary edem a 3. com a 4. hypoten sion an d bradycardia 5. seizures 6. fatal overdose m ay occur w ith any agen t, but is m ore likely w ith syn th et ic opioids such as fen tan - yl (Sublim aze®) am ong users un fam iliar w ith th eir h igh poten cy Reversal of in toxication 50 A test dose of n aloxon e (Narcan®) 0.2 m g IV avoids sudden com plete reversal of all opioid e ect s. If n o sign ifican t react ion occurs, an addition al 1.8 m g (for a total dose of 2 m g) w ill reverse th e toxic- it y of m ost opioids. If n eeded, th e dose m ay be repeated q 2–3 m in utes up to a total of 10 m g, although even larger doses m ay be n eeded w ith pen tazocin e or bupren orph in e (Bupren ex®). Nalox- one m ay precipitate narcotic w ithdraw al sym ptom s in opioid dependent patients, w ith anxiety or agitation , piloerect ion , yaw n in g, sn eezin g, rh in orrh ea, n ausea, vom it in g, diarrh ea, abdom in al cram ps, m uscle spasm s… w h ich are un com fortable but n ot life th reaten in g. Clon idin e (Catapres®) m ay be h elpfu l for som e n arcotic w ith draw al sym ptom s. W ith lon ger act in g opioids, especially m eth adon e (Doloph in e®), repeat doses of n aloxon e m ay be obviated by th e use of n alm efen e (Revex®), a lon g-act in g n arcotic an tagon ist w h ich is n ot appropri- ate for th e in itial t reatm en t of opioid overdosage. 11.4.3 Cocaine 11 Cocain e is extracted from Er yth roxylon coca leaves (an d oth er Er yth roxylon species) an d is th us un related to opioids. It blocks th e re-uptake of n or-epin ephrin e by presyn aptic adren ergic n er ve ter- m in als. It is available in 2 form s: cocain e hydroch loride (h eat labile an d w ater soluble, it is usually taken PO, IV or by n asal in su ation ) an d as th e h igh ly purified cocain e alkaloid (free base or crack cocaine, w hich is heat stable but in soluble in w ater and is usually sm oked). Peak toxicit y occurs 60–90 m in utes after in gestion (except for “body packers”), 30–60 m in utes after sn ort in g, an d m in utes after IV inject ion or sm okin g (freebase or crack).50 Acut e pharm acologic e ect s of cocaine E ects on body system s outside th e n er vous system in clude: tachycardia, acute m yocardial in farc- t ion , arrhyth m ias, rupture of ascen din g aor ta (aort ic dissect ion ), abru ptio placen ta, hyperth erm ia, in testin al isch em ia, an d sudden death . Acu t e p h arm acologic e ect s p er t in en t to t h e n er vou s syst em in clu d e: 1. m en tal status: in itial CNS st im ulation th at first m an ifests as a sen se of w ell-being an d euph oria. Som etim es dysph oric agitation results, occasion ally w ith delirium . St im ulation is follow ed by depression . Paran oia an d toxic psych osis m ay occur w ith overdosage or ch ronic use. Addiction m ay occur 2. pupillar y dilatat ion (m ydriasis) 3. hyper ten sion : from adren ergic stim ulat ion Non -p har m acologic e ect s related to th e n er vou s system 1. pituitar y degen erat ion : from ch ron ic in tran asal use 2. cerebral vasculitis: less com m on than w ith am ph etam in es 3. seizures: possibly related to th e local an esth et ic properties of cocain e 4. stroke51 a) in tracerebral h em orrh age: see In tracerebral h em orrh age, Etiologies (p. 1332) b) subarach noid h em orrh age52,53: possibly as a result of HTN in th e presen ce of an eurysm s or AVMs, h ow ever, som etim es n o lesion is dem on strated on an giography.54 May possibly be due to cerebral vasculitis c) isch em ic st roke55: m ay result from vasocon strict ion d) throm botic stroke50 e) TIA56 5. an terior spinal artery syn drom e56 6. e ect s of m atern al cocain e use on th e fetal n er vous system in clude57: m icroceph aly, disorders of n euron al m igration , n euron al di eren tiation an d m yelin ation , cerebral in farction , subarach n oid an d in tracerebral h em orrh age, an d sudden in fan t death syn drom e (SIDS) in th e postn atal period

208 General and Neurology Treatm ent of toxicit y Most cocain e toxicit y is too sh or t-lived to be treated. An xiety, agitation or seizures m ay be t reated w ith IV ben zodiazepin es, e.g. lorazepam (p. 471). Refractor y HTN m ay be treated w ith n icardipin e (p. 126) or ph en tolam in e (Regit in e®) (p. 655). IV lidocain e used to treat cardiac arrhyth m ias m ay cau se seizu res.50 11.4.4 Am phet am ines Toxicit y is sim ilar to th at of cocain e (see above), but lon ger in duration (m ay last up to several h ours). Cerebral vasculit is m ay occur w ith prolonged abuse w h ich m ay lead to cerebral in farct ion . Elim in at ion of am ph etam ines requires adequate urin e out put. An tipsych ot ic drugs such as h alo- peridol (Haldol®) sh ould n ot be used because of risk of seizures. 11.4.5 Carbon m onoxide General inform at ion Carbon m on oxide (CO) is th e largest source of death from poison in g in th e U.S.A. Norm al cellular fun ct ion requires ≈ 5 m l O2/100 m l blood. Blood n orm ally con tain s ≈ 20 m l O2/ 100 m l. CO bin ds to h em oglobin (Hb) w ith an a n it y ≈ 250 t im es th at of O2, an d it causes a left sh ift of th e Hb/O2 dissociation cur ve. It also bin ds to in tracellular m yoglobin . On ly ≈ 6%of patien ts sh ow th e classic “ch err y-red” color of blood. Clinical findings Clin ical fin din gs related to CO-Hb levels are sh ow n in Table 11.9. Diagnostic st udies 1 1 EKG ch anges are com m on , usually n on -specific ST-T w ave ch anges. In cases of severe in toxication , CT m ay sh ow sym m et rical low atten uat ion in th e globus pallidus; see di eren tial diagn osis (p.1386). Out com e Progn osticators 1. outcom e is m ore closely correlated w ith hypoten sion th an w ith actual CO-Hb level 2. com a 3. m etabolic acidosis 4. EEG 5. CT/MRI ch anges: in on e st udy, th e presen ce of MRI lesion s after 1 m on th did n ot accurately pre- dict subsequen t outcom e 6. CO-Hb level 7. oth er factors probably h ave an e ect , in cluding: age, severit y of exposure Approxim ately 40%of patien ts exposed to sign ifican t levels of CO die. 30–40%h ave t ran sien t sym p- tom s but m ake a full recover y. 10–30%h ave persisten t n eurological sequelae in cludin g CO-en ceph al- opathy (m ay be delayed in on set) – im paired m em or y, irritabilit y, parietal lobe sym ptom s in cluding various agn osias. Brain lesion s: 1. w hite m atter lesions: a) m ultifocal sm all n ecrotic lesion s in deep h em isph eres b) exten sive n ecrotic zon es alon g lateral ven tr icles c) Grin ker’s m yelin opathy (n ot n ecrosis) 2. grey m atter lesions: a) bilateral necrosis of globus pallidus b) lesion s of h ippocam pal form at ion an d focal cort ical n ecrosis

Neurovascular Disorders and Neurotoxicology 209 Table 11.9 Levels of CO-Hb Signs/sym ptom sa CO-Hb level (%) 0–10 none 10–20 m ild H/A, mild DOE 20–30 throbbing H/A 30–40 severe H/A, dizziness, dim ming of vision, impaired judgement 40–50 confusion, tachypnea, tachycardia, possible syncope 50–60 syncope, seizures, com a 60–70 com a, hypotension, respiratory failure, death > 70 rapidly fatal aNB: sm okers may have CO-Hb levels of 15% without signs or sym ptom s Re fe r e n ce s [14] Hun der GG. Gian t Cell (Tem poral) Arteritis. Rh eum 11 Dis Clin N Am er. 1990; 16:399–409 [1] Bart yn ski W S. Posterior reversible en ceph alop athy syn d rom e, p art 1: fun d am en tal im agin g an d clin ical [15] Allen NB, St uden ski SA. Polym yalgia Rheum atica features. AJNR Am J Neuroradiol. 2008; 29:1036– an d Tem p oral Arteritis. Med Clin N Am er. 1986; 1042 70:369–384 [2] Por t JD, Beauch am p NJ. Reversible In tracerebral [16] Hall S, Hun der GG. Is Tem poral Ar tery Biopsy Pru- Pathologic En t ities Med iated by Vascular Au toregu - den t? Mayo Clin Proc. 1984; 59:793–796 lator y Dysfu n ct ion . Radiograp h ics. 1998; 18:353– 367 [17] Caselli RJ, Dan ube JR, Hun d er GG, W h isn an t JP. Periph eral n europathic syn drom es in gian t cell [3] Lin KL, Hsu W C, Wan g HS, Lu i TN. Hyp erten sion - (tem poral) ar teritis. Neurology. 1988; 38:685–689 in du ced cerebellar en ceph alop athy an d hydroce- ph alu s in a m ale. Ped iatr Neurol. 2006; 34:72–75 [18] Salvaran i C, Hu n der GG. Gian t cell ar teritis w ith low er yth rocyte sed im en tation rate: frequ en cy of occu r- [4] Sch aefer PW , Bu on an n o FS, Gon zalez RG, Sch w am m ren ce in a p op ulation-based st udy. Arth rit is Rh eum . LH. Di usion -Weigh ted Im agin g Discrim in ates 2001; 45:140–145 Bet w een Cytotoxic an d Vasogen ic Ed em a in a Pa- t ient w ith Eclam p sia. St roke. 1997; 28:1082–1085 [19] Bau m el B, Eisn er LS. Diagn osis an d Treatm en t of Headach e in the Elderly. Med Clin N Am er. 1991; [5] Covarru bias DJ, Lu etm er PH, Cam p eau NG. Posterior 75:661–675 reversible encephalopathy syndrom e: prognostic utilit y of quan titat ive di usion -w eigh ted MR [20] Karacostas D, Taskos N, Nikolaides T. CT Fin din gs in im ages. AJNR Am J Neu rorad iol. 2002; 23:1038– Tem poral Arterit is: A Repor t of Tw o Cases. Neuro- 1048 rad. 1986; 28 [6] Beeson JH, Du da EE. Com pu ted Axial Tom ograp h y [21] McDon n ell PJ, Moore GW , Miller NR, et al. Tem poral Scan Dem on stration of Cerebral Edem a in Eclam p - Arteritis: A Clin icopathologic St udy. Oph thalm ol- sia Preced ed by Blin d n ess. Obstet Gyn ecol. 1982; ogy. 1986; 93:518–530 60:529–532 [22] Hall S, Lie JT, Kurlan d LT, et al. Th e Th erapeutic [7] Rap s EC, Galetta SL, Broderick M, Atlas SW . Delayed Im pact of Tem poral Artery Biopsy. Lancet. 1983; Perip artu m Vascu lopathy: Cerebral Eclam p sia 2:1217–1220 Revisited. An n Neurol. 1993; 33:222–225 [23] Achkar AA, Lie JT, Hun der GG, O'Fallon W M, Gabriel [8] Dekker GA, Sibai BM. Etiology an d p ath ogen esis of SE. How does previous cort icosteroid treatm en t preeclam psia: cu rren t con cepts. Am J Obstet Gyn e- a ect th e biop sy fin din gs in gian t cell (tem poral) col. 1998; 179:1359–1375 arterit is? An n In tern Med . 1994; 120:987–992 [9] Bar t yn ski W S, Board m an JF, Zeigler ZR, Sh add uck [24] Hunder GG, Kelley W N, Harris ED, Ruddy S, Sledge RK, Lister J. Posterior reversible en cep h alop ath y CB. In : Gian t Cell Arteritis an d Polym yalgia Rh eu - syndrom e in in fection , sepsis, and shock. AJNR Am J m atica. Textbook of Rh eum atology. 4th ed. Ph iladel- Neuroradiol. 2006; 27:2179–2190 ph ia: W . B. Saun ders; 1993:1103–1112 [10] Moore PM, Cu pp s TR. Neurologic Com p lication s of [25] Ken t RB, Th om as L. Tem poral Arter y Biopsy. Am Vascu lit is. An n Neu rol. 1983; 14:155–167 Surg. 1989; 56:16–21 [11] Salvaran i C, Can tin i F, Boiard i L, Hu n der GG. Poly- [26] Ch uan g TY, Hun der GG, Ilstrup DM, et al. Polym yal- m yalgia rh eum atica an d gian t-cell arterit is. N En gl J gia Rh eum atica: A 10-Year Epidem iologic an d Clin i- Med. 2002; 347:261–271 cal Stu dy. An n In tern Med . 1982; 97:672–680 [12] Salvaran i C, Gabriel SE, O'Fallon W M, Hu n der GG. [27] Salvarani C, Gabriel SE, O'Fallon W M, Hunder GG. Th e in cid en ce of gian t cell ar teritis in Olm stead Epid em iology of p olym yalgia rh eu m atica in Olm - Coun t y, Min n esota: app aren t flu ct u ation s in a cyclic pattern . An n In tern Med. 1995; 123:192–194 stead Coun t y, Min n esota, 1970-1991. Arth rit is Rh eum . 1995; 38:369–373 [13] Mach ad o EB, Mich et CJ, Ballard DJ, et al. Tren ds in [28] Cantini F, Salvarani C, Olivieri I, et al. Er yth rocyte In cid en ce an d Clin ical Presen tation of Tem p oral sed im en tation rate an d C-react ive protein in th e Arteritis in Olm stead Coun t y, Min n esota, 1950- evaluation of disease act ivity an d severit y in 1985. Ar th rit is Rh eum . 1988; 31:745–749

210 General and Neurology 11 polym yalgia rh eu m atica: a p rosp ect ive follow -u p [44] Sullivan JT, Sykora K, Sch n eiderm an J, et al. Assess- st ud y. Sem in Arth rit is Rh eu m . 2000; 30:17–24 m en t of Alcoh ol Withdraw al: Th e Revised Clin ical [29] McDon ald TJ, DeRem ee RA. Wegen er's Gran u lom a- In stit ute W ith draw al Assessm en t for Alcoh ol Scale tosis. Lar yn goscope. 1983; 93:220–231 (CIW A-Ar). Br J Addict. 1989; 84:1353–1357 [30] Sn eller MC. Wegen er's Gran ulom atosis. JAMA. 1995; 273:1288–1291 [45] Saitz R, Mayo-Sm ith MF, Roberts MS, et al. In dividu - [31] New Uses of Th alid om id e. Med Letter. 1996; 38:15– alized Treatm en t for Alcoh ol W ith d raw al: A Ran d om ized Double-Blin d Con t rolled Trial. JAMA. 16 1994; 272:519–523 [32] Cu pp s TR, Moore PM, Fauci AS. Isolated An gitis of [46] Lechten berg R, Worn er TM. Seizure Risk W ith th e Cen tral Nervous System : Prospect ive Diagn ostic Recurren t Alcoh ol Detoxification . Arch Neu rol. an d Th erapeu t ic Experien ce. Am J Med. 1983; 1990; 47:535–538 74:97–105 [33] Kaye BR, Fain stat M. Cerebral Vascu litis Associated [47] Addolorato G, Caputo F, Capristo E, Jan iri L, Bern ardi w ith Cocain e Abu se. JAMA. 1987; 258:2104–2106 [34] Hasso AN, Bird CR, Zin ke DE, et al. Fibrom uscular M, Agabio R, Colom bo G, Gessa GL, Gasbarrin i G. Dysplasia of th e In tern al Carotid Artery: Percu tan e- Rapid sup pression of alcoh ol w ith d raw al syn drom e ous Tran slum inal Angioplasty. AJR. 1981; 136:955 – by baclofen . Am J Med . 2002; 112:226–229 960 [48] Treatm en t of Alcohol W ithdraw al. Med Letter. [35] Mett in ger KL. Fibrom u scu lar Dysplasia an d th e 1986; 28:75–76 Brain II: Cu rren t Con cept of th e Disease. St roke. [49] Watson W D, Verm a A, Len art MJ, Quast TM, 1982; 13:53–58 Gauerke SJ, McKen n a GJ. MRI in acute Wernicke's en ceph alopath y. Neurology. 2003; 61 [36] Mett in ger KL, Ericson K. Fibrom u scu lar Dysp lasia [50] Acute React ion s to Drugs of Abuse. Med Letter. an d th e Brain : Obser vation s on An giograph ic, Clin i- 1996; 38:43–46 cal, an d Gen etic Ch aracteristics. Stroke. 1982; [51] Fessler RD, Essh aki CM, Stan kew it z RC, et al. Th e 13:46–52 Neu rovascu lar Com plication s of Cocain e. Surg Neu - rol. 1997; 47:339–345 [37] Osborn AG, An derson RE. An giograph ic Sp ect ru m of Cer vical an d In tracran ial Fibrom u scu lar Dysp lasia. [52] Lich ten feld PJ, Ru bin DB, Feld m an RS. Su barach n oid Stroke. 1977; 8:617–626 Hem orrh age Precipitated by Cocaine Snort in g. Arch Neurol. 1984; 41:223–224 [38] Ch abriat H, Vah edi K, Iba-Zizen MT, et al. Clin ical Spect rum of CADASIL: A St udy of Seven Fam ilies. [53] Oyesiku NM, Colloh an ART, Barrow DL, Reisn er A. Lan cet. 1995; 346:934–939 Cocain e-In du ced An eu r ysm al Rup tu re: An Em er- gent Negative Factor in th e Nat ural Histor y of Int ra- [39] Volt z R, Gultekin SH, Rosen feld MR, et al. A Sero- cranial An eur ysm s? Neurosurger y. 1993; 32:518– 526 logic Marker of Paran eop lastic Lim bic an d Brain - Stem En cepahlitis in Patien ts w ith Testicular Can - [54] Sch w art z KA, Coh en JA. Subarach n oid Hem orrh age cer. N En gl J Med. 1999; 340:1788–1795 Precipitated by Cocaine Snort in g. Arch Neurol. [40] Den ny-Brow n D. Prim ar y Sen sor y Neu rop athy w ith 1984; 41 Muscu lar Ch an ges Associated w ith Carcin om a. J Neurol Neu rosu rg Psych iat r y. 1948; 11:73–87 [55] Levin e SR, Bru st JCM, Fu trell N, Ho KL, et al. Cere- [41] Ch arn ess ME, Sim on RP, Green berg DA. Eth an ol an d th e Nervous System . N En gl J Med. 1989; 321:442– brovascu lar Com p lication s of th e Use of th e 'Crack' 454 Form of Alkaloid al Cocain e. N En gl J Med. 1990; [42] Gorelick PB. Alcoh ol an d stroke. St roke. 1987; 323:699–704 18:268–271 [56] Mody CK, Miller BL, McIn t yre HB, et al. Neu rologic [43] Loh r RH. Treatm en t of Alcoh ol W ith draw al in Hos- Com p lication s of Cocain e Abuse. Neurology. 1988; 38:1189–1193 p italized Patien ts. Mayo Clin Proc. 1995; 70:777– [57] Volp e JJ. E ect of Cocain e Use on th e Fet us. N Engl J 782 Med. 1992; 327:399–407

Part III 12 Plain Radiology and Cont rast Agents 212 Im aging and Diagnost ics 13 Im aging and An g io g r a p h y 227 14 Electrodiagnostics 238 III

212 Im aging and Diagnostics 12 Plain Radiology and Cont rast Agent s 12.1 C-Spine x-rays 12.1.1 Norm al findings For radiograph ic sign s of cer vical spin e t raum a, see Table 63.2, an d for guidelin es for diagn osin g clin ical in stabilit y, see Table 65.4. Cont our lines On a lateral C-spin e x-ray, th ere are 4 con tour lin es (AKA arcuate lin es). Norm ally each sh ould form a sm ooth , gen tle cur ve ( Fig. 12.1): 1. posterior m argin al lin e (PML): alon g posterior cort ical surfaces of vertebral bodies (VB). Marks th e an terior m argin of spin al can al 2. an terior m argin al lin e (AML): alon g an terior cort ical surfaces of VBs WCCL CL B McR ha rd pa la te 12 C1 O McG KEY C2 B = basion, O = opisthion C3 Ba s ila r Line s * McR = McRae's line McG = McGregor's line CL= Chamberlain's line WCCL= Wackenheim's clivus-canal line CONTOUR AML (a nte rior P S L (pos te rior LINES ma rgina l line ) s pinous line ) S LL (s pino- P ML (pos te rior la mina r line ) ma rgina l line ) Fig. 12.1 Spinal contour lines and lines used to diagnose basilar invagination Lateral view through craniocervical junction. * See discussion of the basilar lines (p. 218)

Plain Radiology and Contrast Agents 213 Table 12.1 Norm al ADI m ales ADI Pat ient fe m a le s ≤3 mm a d u lt s ≤ 2.5 mm ≤4 mm pediatrics7 (≤ 15 yrs) 3. spinolam in ar lin e (SLL): alon g base of spin ous processes. Th e posterior m argin of th e spin al can al 4. posterior spin ous lin e (PSL): alon g t ips of spin ous processes Relat ion of at las t o occiput See also criteria for atlan tooccipital dislocat ion (AOD) (p.965). Relat ion of at las t o axis Th ese m easurem en ts are useful for atlan toaxial subluxation /dislocat ion (p. 968) e.g. in t raum a, rh eu- m atoid arth rit is (p. 1134) or Dow n syn drom e (p.1138). 12.1.2 Rule of Spence On AP or open -m outh odon toid x-ray, if th e sum total overh ang of both C1 lateral m asses on C2 is ≥ 7 m m (x + y in Fig. 12.7), th e tran sverse atlan tal ligam en t (TAL) is probably disrupted1,2 (w h en cor- rected for an 18% m agn ificat ion factor, it h as been suggested th at th e criteria be in creased to ≥ 8.2 m m 3) 12.1.3 (Ant erior) at lant odent al int erval (ADI) 12 Note: th e term ADI usually refers to th e an terior atlan toden tal in ter val (th ere is also a posterior ADI (p.213) an d a lateral ADI w h ich can be seen on AP radiograph s). AKA preden tal space. Th e distan ce betw een th e an terior m argin of th e den s an d th e closest poin t of th e an terior arch of C1 (“C1 button”) on a lateral C-spin e x-ray ( Fig. 12.2). Th e n orm al m axim al ADI is variously given in th e ran ge of 2 to 4 m m .4,5 Com m on ly accepted upper lim its are sh ow n in Table 12.1. An abn orm ally in creased ADI is a surrogate m arker for TAL disruption6 12.1.4 Post erior at lant odent al int erval (PADI) AKA th e n eural can al w idth (NCW ).8 Th e PADI is th e AP diam eter of th e bony can al at C1 an d is m eas- ured from th e back of th e odon toid to th e an terior aspect of th e posterior C1 rin g ( Fig. 12.2). It is m ore useful th an th e ADI for som e con dition s, e.g. AAS in rh eum atoid arth rit is (p. 1134) or Dow n syn drom e (p.1138). PADI Fig. 12.2 The atlantodental interval (ADI) (p. 213) and C1 posterior atlantodental interval (PADI) on a lateral C-spine x-ray ADI C2

214 Im aging and Diagnostics Table 12.2 Normal prevertebral soft tissue Sp a ce Le ve l Maxim um norm al widt h (m m ) Adult s Pe d s MDCT Lat eral X-Ray re t ro p h a r yn g e a l C1 8.5 10 unreliable C2–4 6–7a 5–7 re t rot rach e a l C5–7 18 22 14 aCT data was deemed unreliable at C411 Canal diam et er Norm al can al diam eter on lateral C-spin e x-ray (from spin olam in ar lin e (SLL) to posterior ver tebral body w ith 6 foot tube to film distan ce)9: 17 ± 5 m m . In th e presen ce of osteophytic spurs, m easure from th e back of th e spur to th e SLL. Cer vical spin al stenosis: various cuto s for th e n orm al m in im um AP diam eter h ave been sug- gested.10 On a plain lateral C-spin e x-ray th is is usually m easured from th e posterior vertebral body (or th e posterior aspect of an osteophyte) to th e spin olam in ar lin e. Som e use 15 m m . Most agree th at stenosis is presen t w h en th e AP diam eter is < 12 m m in an adult. Th is m easurem en t is less critical th an it once w as, it is a surrogate m arker for sten osis severe en ough to com press th e spin al cord, w h ich n ow m ay be dem on st rated directly w ith MRI (or m yelography). Prevert ebral soft t issue Abn orm ally in creased prevertebral soft tissue (PVST) m ay in dicate th e presen ce of a vertebral frac- t ure, dislocation , or ligam en tous disruption .12 Norm al values for lateral C-spin e x-ray an d CT scan 1 2 are sh ow n in Table 12.2. Plain film s are subjcet to errors due to m agn ification an d rotation . Multi- detector CT (MDCT) elim in ates th ese sh ortcom ings.11 In creased PVST is m ore likely w ith an terior th an posterior injuries.13 NB: th e sen sitivit y of th ese m easurem en ts is on ly ≈ 60% at C3 an d 5% at C6.12 False positives m ay occur w ith basal skull/facial fract ures, especially w ith fract ure of th e pter ygoid plates. An ET-tube m ay allow fluid to accum ulate in th e posterior oroph ar yn x w h ich can obscure th is m easurem en t. In th is sett in g, on e can look for a th in fat layer betw een th e prevertebral m uscles an d th e posterior ph ar yn x on cer vical CT; th e pre- vertebral tissue (posterior to this line) w ill be th ickened (no m easurem ents available at this tim e). MRI can also dem on strate abn orm al sign al w ith in the prever tebral tissue. Int erspinous dist ances C-spin e AP: a fract ure/dislocat ion or ligam en t disruption m ay be diagn osed if th e in terspin ous dis- tan ce is 1.5 t im es th at at both adjacen t levels (m easured from cen ter of spin ous processes ).14 Also look for a m alalign m en t of spin ous processes below a certain level w h ich m ay be evidence of rota- t ion due to a un ilaterally locked facet. C-spin e lateral: look for “fan n in g” or “flar in g” w h ich is an abn orm al spread of on e pair of spin ous processes th at m ay also in dicate ligam en t disruption . 12.1.5 Pediat ric C-spine C1 (at las) Ossification cen ters15: usually 3 ( Fig. 12.3) ● 1 (som et im es 2) for body (n ot ossified at birth ; appears on x-ray durin g 1st yr) ● 1 for each n eural arch (appear bilaterally ≈ 7th fetal w eek) Syn ch on d roses15: ● syn ch on drosis of th e spin ous process: fuses by ≈ 3 yrs age ● 2 n eurocen tral syn ch on droses: fuse by ≈ age 7 yrs

Plain Radiology and Contrast Agents 215 AP VIEW neural Fig. 12.3 Pediatric C1 (atlas) n e u ro ce n t ra l arch synchondrosis body body VIEWED neural FROM ABOVE arch synchondrosis of spinous process os term inale n e u ro ce n t ra l synchondrosis neural neural neural dens neural arch arch arch arch body d e n t o ce n t ra l n e u ro ce n t ra l 12 synchondrosis synchondrosis VIEWED FROM ABOVE AP VIEW Fig. 12.4 Pediatric C2 (axis) Th e ossification cen ters of C1 fail to com pletely close in 5% of adults (usually posteriorly). W h en presen t, th e rare an terior defect is usually associated w ith a posterior defect . C2 (axis) Developm en tally th ere are 5 ossification cen ters. Th e t w o h alves of th e odon toid fuse togeth er in th e m idlin e (dash ed lin e in Fig. 12.4) at 7 m on th s developm en t, so th at at birth th ere are 4 prim ary ossification cen ters ( Fig. 12.4): ● odon toid process ● vertebral body ● 2 n eural arch es Th e posterior arch es fuse together by 2-3 years of age. Th e an terior syn chon droses n orm ally fuse betw een 3-6 years of age. How ever, th e den tocen tral syn ch on drosis (AKA subden tal syn chon drosis) m ay be visible on x-ray until ≈ 11 years of age. A secondary ossification cen ter (os term inale) appears at th e sum m it of th e den s bet w een 3–6 years of age, an d fuses w ith th e den s by age 12 years.15 C3–7 Fig. 12.5). 3 ossification centers at birth16 (see ● vertebral body ● 2 n eural arch es

216 Im aging and Diagnostics Fig. 12.5 Pediatric C3-7 n e u ro ce n t ral syn ch o n d ro se s body neural p o st e rio r arches synchondrosis VIEWED FROM ABOVE Th e 2 n eural arch es fuse togeth er posteriorly by 2-3 years age. Th e n eural arch es each fuse to th e body by 3-6 years age. Cer vical bodies are n orm ally sligh tly w edge sh aped in pediatric population (n arrow er an teriorly). Wedging decreases w ith age. 12.2 Lum bosacral (LS) spine x-rays L4–5 is n orm ally th e lum bar disc space w ith th e greatest vert ical h eigh t. Also see Norm al LS spin e m easurem en ts (p.1102). AP view : look for defect or n on visualization of th e “ow l’s eyes” w h ich is due to pedicle erosion 12 w hich m ay occur w ith lytic tum ors (com m on w ith m etastatic disease). Oblique view s: look for discon tin uit y in n eck of “Scott y dog” for defect in pars in terar ticularis. Bu t t erfly ver t ebra: An un com m on congen ital an om aly th ough t to arise from failure of fusion of th e lateral h alves of th e VB due to persistent n otoch ord tissue, producin g a “butterfly” appearan ce on AP x-rays or coron al CT scan recon struct ion s. Th e involved VB is w iden ed, an d adjacen t vertebrae m ay sh ow a com pen sator y deform it y as if to fill in som e of th e gap. May be associated w ith oth er spinal an d rib m alform at ion s.17 On lateral view s m ay sim ulate com pression fract ure. In severe cases, th ere m ay be sign ifican t kyph osis an d/or scoliosis. Often asym ptom atic, requirin g n o treatm en t. May be associated w ith lipom yelom en ingocele (p. 269). 12.3 Skull x-rays Water’s view : AKA subm en tal vertex view. X-ray tube angled up 45° (perpen dicular to clivus). Tow n e’s view : x-ray tube an gled dow n 45°, to view occiput . 12.3.1 Sella t urcica Norm al adult dim ensions on skull x-ray Techn ique: t rue lateral, 91 cm target to film distan ce, central ray 2.5 cm an terior an d 1.9 cm superior to EAM. Table 12.3 sh ow s n orm al values ( Fig. 12.6 sh ow s h ow m easurem en ts are m ade). Depth (D): defin ed as th e greatest m easurem en t from floor to diaph ragm a sellae. Len gth (L): defin ed as th e greatest AP diam eter. Abnorm al findings Pituit ary aden om as ten d to en large th e sella, in con trast to cran ioph aryn giom as w h ich erode th e posterior clinoids. Em pt y sella syn drom e tends to balloon th e sella sym m etrically, an d also does n ot erode th e clin oids. Tuberculum m en in giom as usually do n ot en large th e sella, an d m ay be associated w ith enlargem ent of the sphenoid sinus; see sphenoid pneum osinus dilatans (p.1372).

Table 12.3 Norm al sella turcica dim ensions ( Fig. 12.6) Plain Radiology and Contrast Agents 217 Dim ension Max Min Avg 4 8.1 D (depth) (mm ) 12 5 10.6 L (length) (mm ) 16 d ia p h ra g m a Fig. 12.6 Measurem ents of the sella turcica (lateral sellae view) L D L= length D = depth “J” sh aped sella suggests optic n er ve gliom a. It can also occur congen itally in Hurler syn drom e (a 12 m ucopolysacch aridosis). 12.3.2 Basilar invaginat ion and basilar im pression (BI) Term inology Th e term s basilar im pression an d basilar invagin ation are often used in terch angeably in th e litera- t ure: h istorically, basilar invagin ation (AKA cran ial settling) den oted upw ard in den tation of sku ll base usually due to acquired soften ing of bon e (see below ), often associated w ith atlan to-occipital fusion , w h ile basilar im pression im plied n orm al bon e. Making a distin ct ion seem s poin tless (th e abbreviation (BI) w ill be used for eith er). Com m on feature: upw ard displacem en t of th e upper cer vi- cal spin e (in cludin g odon toid process, AKA cran ial m igration of th e odon toid) th rough th e foram en m agn um in to th e p -fossa. Plat ybasia: flatten ing of th e skull base. Origin ally assessed on plain x-rays (w h ich are subject to error due to skull rotation or di culty identifying landm arks), n ow m ore com m only evaluated on CT or MRI. May or m ay n ot be associated w ith BI, an d m ay occur in association w ith cran iofacial abn orm alit ies, Ch iari m alform at ion , Paget’s disease… Quan titated by m easurin g th e basal an gle, w h ich on plain x-rays, m easured th e an gle betw een lin es draw n from th e n asion to cen ter of sella an d th en to th e an terior foram en m agn um ,18 but on MRI w as felt to be better represen ted by th e an gle betw een a lin e draw n alon g th e floor of th e an te- rior fossa to th e dorsum sellae an d a secon d lin e draw n alon g th e posterior clivus.19 Norm al m ean basal an gle: 130°. Plat ybasia: > 145° (abn orm ally obtuse basal an gle). Tw o subt ypes of BI See referen ce.20 Type I: BI w ith out Ch iari m alform ation . Tip of odon toid ten ds to be above CL, McR, an d W CCL in Fig. 12.7. Brain stem com pression is due to odon toid process invagin at ion . 85%can be reduced w ith t ract ion . Treatm en t: tran soral surger y is recom m en ded, usually accom pan ied by posterior fusion Type II: BI + Ch iari m alform at ion . Odon toid t ip ten ds to be above CL, but n ot McR or WCCL. Brain - stem com pression is due to reduced p -fossa volum e. On ly 15% can be reduced w ith traction . Fora- m en m agn um decom pression is appropriate

218 Im aging and Diagnostics m astoid process digastric notch FDGL C1 FBML x odontoid process C2 y C1 lateral m ass C2 lateral m ass Fig. 12.7 AP view through craniocervical junction FDGL= Fischgold’s digastric line, FBML= Fischgold’s bim astoid line, x + y = total overhang of C1 on C2; see Rule of Spence (p. 970) Measurem ent s used in BI ( Fig. 12.1 an d Fig. 12.7): 1. McRae’s lin e (“McR” in Fig. 12.1): draw n across foram en m agn um (tip of clivus (basion ) to opis- th ion ).21 Th e m ean position of th e odon toid tip below th e lin e is 5 m m (± 1.8 m m SD) on CT an d 4.6 m m (± 2.6 m m SD) on MRI.22 No part of odon toid sh ould be above th is lin e (th e m ost accurate m easure for BI). 2. Ch am berlain’s lin e (“CL” in Fig. 12.1)23: posterior h ard palate to posterior m argin of foram en m agn um (opisth ion ). Less th an 3 m m or h alf of den s sh ould be above th is lin e, w ith 6 m m being 1 2 defin itely path ologic. Seldom used because th e opisth ion is often h ard to see on plain film an d m ay also be invagin ated. On CT24 an d MRI22 th e n orm al odon toid tip is 1.4 m m (± 2.4) below th e lin e 3. McGregor’s baselin e (“McG” in Fig. 12.1)25: posterior m argin of h ard palate to m ost caudal poin t of occiput . No m ore th an 4.5 m m of den s sh ould be above th is. On CT24 an d MRI22 th e n or- m al odon toid t ip is 0.8 m m (± 2.4) above th e lin e 4. Wacken h eim ’s clivus-can al lin e (“WCCL” in Fig. 12.1): th e odon toid sh ould be tan gen tial to or below th e lin e th at exten ds th e course of th e clivus (th e clivus baselin e). If th e clivus is con cave or convex, this baseline is draw n to con nect the basion to the base of the posterior clinoids on th e clivu s26 5. (Fisch gold’s) digastric lin e (“FDGL” in Fig. 12.7): join s th e digastric n otch es. Th e n orm al distan ce from th is lin e to th e m iddle of th e atlan to-occipital join t is 10 m m (decreased in BI).27 No par t of odon toid sh ould be above th is lin e. More accurate th an th e bim astoid lin e (FBML) 6. Fisch gold’s bim astoid lin e (“FBML” in Fig. 12.7): join s tips of m astoid processes. Th e odon toid tip averages 2 m m above this line (range: 3 m m below to 10 m m above) and this line should cross th e atlan to-occipital join t Condit ions associat ed w it h BI 1. congen ital con dition s (BI is th e m ost com m on congenital an om aly of th e cran iocer vical jun ct ion , it is often accom p an ied by oth er an om alies28 (p 148–9)) a) Dow n syn drom e b) Klippel-Feil syn drom e (p. 271) c) Ch iari m alform at ion (p. 277): in a series of 100 patien ts, 92 h ad BI29 d) syrin gom yelia 2. acquired conditions a) rh eum atoid arth rit is (in part due to in com peten ce of tran sverse ligam en t, see Basilar im pres- sion in rheum atoid arthrit is (p.1137) b) post-traum atic 3. con dition s w ith BI associated w ith soften in g of bon e in clude30: a) Paget’s disease

Plain Radiology and Contrast Agents 219 b) osteogen esis im perfecta: patien ts h ave blue discolored sclera an d early h earing loss an d due to a genetic defect th at causes defect ive Type 1 collagen . Bon es are w eak (”brit tle-bon e dis- ease”). Autosom al dom in an t in h eritan ce. Th ere are 4 com m on t ypes of OI an d som e un com - mon ones c) osteom alacia d) rickets e) hyperparathyroidism 12.4 Cont rast agent s in neuroradiology Also see In traoperative dyes (p. 1426) for visible dyes useful in th e operat in g room . 12.4.1 Iodinat ed cont rast agent s General precaut ions Water-soluble contrast agen ts have superseded non-water-soluble ones such as Pantopaque® (ethyl iodoph enylun decylate or ioph en dylate m eglum in e). Caution : iodin ated con trast (IV or in t ra-arterial) m ay delay excret ion of m etform in (Gluco- ph age®, Avan dam et®), an oral hypoglycem ic agen t used in diabetes t ype II, an d can be associated w ith lact ic acidosis an d ren al failure (part icularly in patien ts w ith CHF or th ose con sum ing alcoh ol). Th e m an ufact urer recom m en ds w ith h olding m etform in 48 h rs prior to an d follow in g con trast adm in istration (or lon ger if th ere is evidence of declin ing ren al fun ct ion follow in g use of con trast). Metform in sh ould also be h eld ≈ 48 h ours before any surger y, an d sh ould n ot be restarted post-op un til th e patien t h as fully recovered an d is eatin g an d drin kin g n orm ally. Maxim um dose of iodin e w ith n orm al ren al fun ct ion is ≈ 86 gm in a 24 h our period. Int rat hecal contrast agent s 12 Inadvertent intrathecal injection of unapproved cont rast agents Caution : serious react ion s can occur w ith in adverten t in trath ecal inject ion (e.g. for m yelography, cistern ography, ven triculography…) of iodin ated con trast m edia th at are n ot specifically in dicated for in t rath ecal use (in cludin g ion ic con trast agen ts as w ell as som e n on -ion ic agen ts (e.g. Optiray®, Ren o-60…)). Th is can cause un con trollable seizures, in tracerebral h em orrh age, cerebral edem a, com a, paralysis, arach n oidit is, m yoclon us (ton ic-clon ic m uscle spasm s), rh abdom yolysis w ith subse- quen t ren al failure, hyper th erm ia, an d respirator y com prom ise, w ith a sign ifican t fatalit y rate.31 Man agem en t suggestion s for in adverten t in trath ecal injection in clude: 1. im m ediately rem ove CSF + con trast if th e error is recogn ized w h en th e opport un it y is available (e.g. w ith draw fluid th rough m yelography n eedle) 2. elevate head of bed ≈ 45° (to keep contrast out of head) 3. if th ere is a question about w h at m ay h ave occurred (i.e. it is n ot certain if an in appropriate con - trast agen t w as used) sen d blood an d CSF w ith con trast for h igh -perform an ce liquid ch rom atog- raphy for iden tification of agen t32 4. an tih istam in es: e.g. diph en hydram in e (Ben adr yl®) 50 m g deep IM 5. respiration: supplem ental oxygen, and if needed, intubation 6. con trol HTN 7. IV hydrat ion 8. IV steroids 9. sedation if patient is agitated 10. treat fever w ith acetam in oph en an d if n eeded w ith a coolin g blan ket 11. ph arm acologic paralysis if n ecessar y to m an age m uscle activit y 12. an ticonvulsan t m edication : m ore th an on e agen t m ay be required (e.g. ph enytoin + ph en obarbi- tal + a ben zodiazepin e) 13. con sider un en h an ced brain CT scan : m ay h elp assess if con trast h as di used in t racran ially, but this requires placing patient flat and m ay not be advisable 14. in sert lum bar subarach noid drain w ith CSF drain age (e.g. 10 cc q h r) 15. m on itor: elect rolytes, an ticonvulsan t levels, creatin e kin ase (CK) 16. repeat EEGs to assess seizure act ivit y w h ile sedated/paralyzed Iohexol (Om nipaque®) Th e prim ar y approved agen t em ployed for in t rath ecal use today is ioh exol (Om n ipaque®).

220 Im aging and Diagnostics A n on -ion ic t riiodin ated com poun d. Con cen t ration is expressed as follow s: e.g. Om n ipaque 300 contain s th e equivalen t of 300 m g of organ ic iodin e per m l of m edia (300 m gI/m l). Used for m yelography, cistern ography as w ell as IV con trasted CT. Uses an d con cen tration s are sh ow n in Table 12.4. In t rat h ecal u se NB: on ly Om n ipaque 180, 210, 240 an d 300 are labeled for in trath ecal use. 140 an d 350 are not FDA approved for in trathecal use, h ow ever, som e n euroradiologists w ill use Om n ipaque 140 or diluted 180 e.g. for CT ven triculography (o -label usage). Con sider discon tin uing n eurolept ic drugs (in cludin g: ph en oth iazines, e.g. ch lorprom azin e, pro- ch lorperazin e, an d prom eth azin e) at least 48 h ours prior to procedure. Elevate HOB≥ 30° for th e first few h ours after th e procedure. Hydrate orally or IV. Use w ith caution in patien ts w ith seizure h istor y, severe cardiovascular disease, ch ron ic alcoh ol- ism or m ultiple sclerosis. Ioh exol un dergoes slow di usion from th e in t rath ecal space to th e system ic circulat ion an d is elim in ated by ren al excret ion w ith n o sign ifican t m etabolism or deiodin at ion . Maxim um dosage: a total dose of 3060 m g iodine should not be exceeded in an adult during a sin gle m yelogram (som e say up to 4500 m g is OK) (e.g. 15 cc of Om n ipaque 300 = 15 m l × 300 m gI/ m l= 4500 m g of iodine). Iopam idol (e.g. Isovue 300, Isovue 370®) Triiodin ated, n on -ion ic, w ater-soluble. Used for in t ravascular an d in t rath ecal radiograph ic con trast. Isovue 300 an d 370 con tain s 300 an d 270 m g iodin e/m l, respect ively. Table 12.4 Iohexol concentrations for adults Concent rat ion Volum e Pr o ce d u r e (m gI/m l) (m l) lumbar m yelography 180 10–17 via LP 240 7–12.5 1 2 thoracic myelography 240 6–12.5 via LP or cervical injection 300 6–10 cervical m yelography 240 6–12.5 via LP 300 6–10 cervical m yelography 180 7–10 via C1–2 puncture 240 6–12.5 300 4–10 com plete myelography 240 6–12.5 via LP 300 6–10 cerebral arteriographya 300 ≈ 6–12 ml/vessel IV contrast enhanced CT scan of the brain 240 120–250 ml IV drip 350 70–150 m l bolusb CT cisternography 300 12 via LP or C1–2 puncture 350 12 CT ventriculography via ventricular catheter 180c 2–3 plain film ventriculography via ventricular catheter 180 2–3 plain film “shunt-o-gram ” injected via shunt into ventricles 180 2–3 plain film “shunt-o-gram ” 300 10–12 10–12 injected via shunt distal to valve so as not to enter into ventricles (to 350 check distal shunt function) am ost centers use Optiray®, see text bfollow with 250 ml bolus of 0.45% NS to rehydrate patient c180 will be very dense on CT, and som e use 1–3 m l of 140 or diluted 180%(dilute approxim ately 2 parts contrast to 1 part preservative-free norm al saline)

Plain Radiology and Contrast Agents 221 Non-int rat hecal contrast agent s For in adverten t in trath ecal injection of con trast agen ts not in ten ded for in t rath ecal use, see above. Ioversol (Optiray®) Not for in t rathecal use (see above). Uses an d con cen tration s in clude: ● arteriography: Optiray 300 (ioversol 64%) or Optiray 320 (ioversol 68%). Total procedural dose sh ould n ot usually exceed 200 m l ● IV con trast en h an ced CT scan of brain : a) adult: 50–150 m l of Optiray 300, 320, or 100–250 m l of Optiray 240. Typically: 100 m l of Optiray 320 b) pediatrics: 1–3 m l/kg of Optiray 320 Ioprom ide (Ultravist®) Not for in trath ecal use (see above). Available in 150, 240, 300 & 370 m g iodin e/m l. Osm olalit y of Ult ravist 300 is 607. Cerebral an giography (300 m g/m l): m axim um dose is 150 m l per procedure. Con trast en h an ced CT (CECT) (300 m g/m l). Pedia tr ics (> 2 years age): t ypical dose in is 1–2 m l/ kg IV, m axim um dose is 3 m l/kg per procedure. Adult:t ypical dose is 50–200 m l, m axim um dose is 200 m l. Iodixanol (Visipaque®) Not for in t rathecal use (see above). Triiodin ated, n on -ion ic, isosmola r to blood. For in travascular use. FDA approved for CECT, som e an giograph ers use Visipaque 270 for cerebral an giography (sligh tly low er opacification , but also sligh tly low er iodin e dose). Available in 270 an d 320 m g iodine/m l. Iodinat ed cont rast w it h allergies or renally insu ciency 12 Allergy prep In dicated for patien ts w ith previous h istor y of react ion to IV iodin ated con trast m aterial. Min or pre- vious reaction s such as h ives an d itch in g m erit preparation w ith th is regim en w h en ever possible. Pat ien ts w ith an aphylact ic sh ock or severe edem a causin g com prom ise of th e airw ay sh ould prob- ably n ot receive IV iodin e even w ith th is prep, un less absolutely n ecessary. Caut ion : in spite of th is regim en , th e patien t m ay st ill h ave serious react ion (m odified33). Th is prep h as also been used for the rare gadolin ium allergy. 1. utilize n on -ion ic con trast m edium (e.g. ioh exol) w h en ever possible 2. have em ergency equipm ent available during study 3. m edications: a) steroid ( Table 8.1 for fur th er details of steroid dosing) ● predn ison e 50 m g PO: 20–24 h rs, 8–12 h rs & 2 h rs before st udy ● equivalen t dose of IV Solum edrol® (m ethylpredn isolon e): ≈ 25 m g b) diph en hydram in e (Ben adr yl®) 50 m g, EITHER IM 1 h r before, OR IV 5 m in before study c) option al: H2 an tagon ist, e.g. cim etidin e 300 m g PO or IV 1 h r before study Medicat ion s for an emergency scan w h en 24 h our prep is n ot possible: ● hydrocort ison e 100 m g IV th en scan w ith in 2 h ours Prep for renal insu ciency or patients with DM For pat ien ts w ith DM or m ild ren al in su cien cy (e.g. sligh t serum creatin in e elevation , > 1.2 m g/dl (U.S.) w h ich is > 100 m cm ol/L) 1 m g/dl of creatin in e (used in th e U.S.) = 88.4 m cm ol/L, to m itigate against iodin e con trast-in duced nephropathy: ● N-acet yl cystein e (Mucom yst; th e act ual e cacy of NAC h as n ot been proven , an d m ay be n o bet- ter th an hydration alon e): regim en s all accom pany hydration an d in clude: a) 800 m g PO q 8 h rs for 24 h ours before th e st udy,34 follow ed by 600 m g PO BID for 24 h ours after th e st udy b) 600 m g PO BID X 2 days before th e st udy, 600 m g PO BID for 24 h ours after c) 600-m g IV bolus before th e study, an d 600 m g PO BID for 48 h ours after35

222 Im aging and Diagnostics ● hydration : 1 L of sterile w ater w ith 3 am ps of sodium bicarbon ate IV at 100 m l/h r, start 1 h our prior to th e study, an d con tin ue un til en tire L given 12.4.2 React ions t o int ravascular cont rast m edia General inform at ion See also t reatm en t of in adverten t in trath ecal inject ion of ion ic con trast agen ts (p.219) Beta blockers Beta blockers can in crease th e risk of con trast m edia react ion s, an d m ay m ask som e m an ifestation s of an an aphylactoid react ion . Th ey also m ake use of epin eph rin e in advisable sin ce th e alph a e ects of epin eph rin e w ill predom in ate (bron ch ospasm , vasocon st rict ion , in creased vagal ton e). If treat- m en t is required for hypoten sion after beta-blocker adm in istration , m ay t r y glucagon 2–3 m g IV bolus, follow ed by 5 m g IV drip over 1 h our (glucagon h as positive in otropic an d ch ron otropic e ect th at is n ot m ediated th rough adren ergic path ways). Idiosyncrat ic react ions and t reat m ent Hypotension with tachycardia (anaphylactoid reaction) 1. m ild: Tren delen burg position . IV fluids 2. if no respon se but rem ains m ild: epin eph rin e (use w ith caution in patien ts w ith coron ar y ar tery disease, lim ited cardiac reserve, hypertension, or unclipped cerebral aneurysm ) a) 0.3–0.5 m l of 1:1000 SQ (0.3–0.5 m g) q 15–20 m in s (peds: 0.01 m g/kg) b) or, ASEP recom m en dation s (especially for elderly or patien ts in sh ock): 10 m l of 1:100,000 IV over 5 to 10 m in (put 0.1 m l of 1:1000 in 10 m l of NS, or dilute 1 am p of 1:10,000 to 10 m l w ith NS) 3. m oderate to severe or w orsening (anaphylaxis): add: a) IV colloidal fluids, e.g. h etastarch (Hespan ®) 6%(colloids are required sin ce th ere is extrava- scular sh ift of fluids due to see page, th ese agen ts also carr y a sm all risk of allergic react ion ) 12 b) epinephrine (see above). May repeat × 1 c) O2 2–6 L/m in per NC. In tu bate if n ecessary d) EKG to R/O isch em ic ch anges 4. if sh ock develops: add dopam ine (p.128), start at 5 m cg/kg/m in Hypotension with bradycardia (vasovagal react ion) 1. m ild: a) Tren delen burg position b) IV fluids 2. if no respon se, add: a) atropin e 0.75 m g IV, m ay repeat up to 2–3 m g over 15 m in s PRN. Use w ith caution in patien ts w ith underlying heart disease b) EKG an d/or cardiac m on itor: especially if atropin e or dopam in e are used 3. if no respon se: add dopam ine (p.128), start at 5 m cg/kg/m in Ur t ica ria 1. m ild: self lim ited. No treatm en t necessar y 2. moderate: a) diph en hydram in e (Ben adr yl®) 50 m g PO or deep IM (avoid IV, can cause an aphylaxis itself) b) cim et idin e (Tagam et®) 300 m g PO or IV diluted to 20 m l an d given over 20 m in s. H2 receptors contribute to w heal and flare of reaction 3. severe: treat as above for m oderate react ion , an d add: a) epin eph rin e (see above) b) m ain tain IV lin e Facial or laryngeal angioedem a 1. epin ephrine: see above. May repeat up to 1 m g 2. if respirator y distress: O2 2–6 L/m in . In tu bate if n ecessary (orotrach eal m ay be ver y di cult due to sw ellin g of tongue, nasotracheal intubation or em ergency cricothyrotom y m ay be required)

Plain Radiology and Contrast Agents 223 3. diphenhydram ine: see above 12 4. cim etidin e: see above 5. if an gioedem a is accessible, add ice pack 6. m ain tain IV lin e 7. steroids are usually e ect ive on ly for chronic an gioedem a Br o n ch o sp a sm 1. m ild to m oderate: a) epin ephrin e: see above. May repeat up to 1 m l b) if respirator y distress: O2 2–6 L/m in . In tu bate if n ecessary c) m ain tain IV lin e d) in h alat ion al th erapy w ith a β-adren ergic agon ist, e.g. albuterol (Proven til®) if respirator y th erapy is available, oth erw ise, m etered dose in h aler e.g. pirbuterol (Maxair®) or m etaproter- enol (Metaprel®), 2 pu s 2. severe: treat as above for m oderate react ion , an d add: a) am in ophyllin e 250–500 m g in 10–20 cc NS slow IV over 15–30 m in s. Mon itor for hypoten sion an d arrhyth m ias b) intubate 3. prolonged: add th e follow in g (w ill n ot h ave im m ediate e ect ): a) hydrocort ison e 250 m g IV b) diphenhydram in e: see above c) cim etidine: see above Pulm onary edem a 1. O2 2–6 L/m in per NC. In tu bate if n ecessary 2. raise head and body 3. furosem ide (Lasix®) 40 m g IV 4. EKG 5. if hypoxia develops (m ay m an ifest as agitation or com bativen ess), add: a) m orph in e 8–15 m g IV. May cause respirator y depression , be prepared to in t ubate b) epin eph rin e: see above. CAUTION: use on ly if MI can be R/O as cause of th e pulm on ar y ede- m a. Pat ien ts w ith acute in t racran ial path ology m ay be at risk of n eurogen ic pulm on ar y edem a (p . 1 1 7 8 ) Se izu r e s If seizure is n ot self lim ited, start w ith lorazepam (Ativan ®) 2–4 m g IV for an adult . Take precaution s for status epilept icus (p.470) an d proceed to oth er drugs as in dicated (p.471). 12.5 Radiat ion safet y for neurosurgeons 12.5.1 General inform at ion Radiation exposure h as both a determ in ist ic com pon en t (exposure over a certain th reshold w ill cause a specific injur y) as w ell as a stoch ast ic com pon en t (any dose in creases th e cha nces of an adverse even t, an d th e h igh er th e cum ulative dose, th e h igh er th e ch an ces). 12.5.2 Unit s See referen ce.36 Absorbed dose: th e am oun t of en ergy absorbed per un it m ass. Expressed in Gray or rads. Gray (Gy): th e SI un it . 1 Gy = 100 cGy = 100 rads = an absorbed dose of 1 Joule/kg. Rad: 1 rad = an absorbed dose of 100 ergs/gram = 0.01 joule/kg = 0.01 Gy = 1 cGy. Th e biological e ect (dose equivalen t) of radiation : can be expressed in rem or Sieverts. Sievert (Sv): th e SI un it . Th e dose equivalen t in sieverts is equal to th e absorbed dose in grays m ultiplied by a “qualit y factor” (Q) w h ich di ers for di eren t sources of radiation , e.g. h igh -en ergy proton s h ave a Q of 10, x-rays h ave a Q of 1. 1 Sv=100 rem s. Roen tgen -equivalen t m an (rem ): th e absorbed dose in rads m ult iplied by Q. 1 rem is estim ated to cause ≈ 300 addit ion al cases of can cer per m illion person s (on e th ird of w h ich are fatal). 1 rem = 0.01 sie ve r t .

224 Im aging and Diagnostics 12.5.3 Typical radiat ion exposure Th e average an n ual exposure to radiation is 360 m rem (about 30 m rem are due to backgroun d cos- m ic radiation , ≈ 20% of th e total dose is due to radioact ive potassium -40 w h ich is in ever y cell). Exposure from a t ran scon tin en tal airlin e fligh t is ≈ 5 m rem . CXR: causes about 0.01–0.04 rem of exposure to th e ch est. Spin e x-ray w ith obliques: 5 rem . CAT scan (brain , n on con trast): m edian e ect ive dose to th e h ead = 0.2 rem , but th e ran ge varied 13 fold w ith in an d across in stitution s.37 Spin e CT: 5 rem . Cerebral arteriogram : ≈ 10–20 rem (in cludin g fluoroscopy).38 Cerebral em bolizat ion : 34 rem . Bon e scan : 4 rem . C-arm fluoroscopy39: exposure is sh ow n in Table 12.5. Doses durin g a m in im ally invasive TLIF40: Pat ien t exposure: m ean 60 m Gy to th e skin in th e AP plan e (ran ge: 8–250 m Gy), 79 m Gy in th e lateral plan e. Surgeon exposure: 76 m rem to dom in ant h an d, 27 m rem at th e w aist un der a lead apron , an d 32 m rem to an unprotected thyroid level detector. 12.5.4 Occupat ional exposure Th e U.S. Nuclear Regulator y Com m ission (NRC) m axim al recom m en ded an n ual occupation al dose lim its for radiation are sh ow n in Table 12.6.41 Th e 1990 recom m en dation s of th e In tern at ion al Com m ission on Radiological Protect ion (ICRP) w as to keep exposure ≤ 2 rem /year averaged over 5 ye a r s .4 2 ALARA: an acronym for “As Low As Reason ably Ach ievable” by w h ich th e NRC m ean s m akin g ever y reason able e ort to keep radiation dose as far below th e lim its as possible con sisten t w ith th e purp ose for w h ich th e licen sed act ivity is un dertaken .43 Steps to reduce occupat ion al radiation dose (to sta ) durin g surgery: 1. in crease th e distan ce from th e radiation source: radiation exposure is proportion al to th e inverse squa re of th e distan ce. Conven t ion al w isdom is to t r y to keep 6 feet aw ay. In a AANS 12 publication , 3 m (10 ft) w as recom m ended44 Lead apron s/sh ields m ay or m ay n ot w ork. Distan ce ALW AYS w orks45 (inverse square law – dou- ble th e distan ce an d get 1/4 th e radiation ). 2. sh ieldin g: sh ieldin g is less e ect ive at h igh er kV (used w ith larger patien ts). Por table lead “doors” are m ore e ective th an apron s. Wrap -aroun d 2-piece apron s are better th an fron t side apron s. W ith fron t apron s th e w earer m ust always face th e x-ray source, oth erw ise th e apron can act ually reflect som e radiation back on to th e w earer. Non -lead apron s m ay n ot provide th e rated protect ion at levels > 100 keV46 3. don’t overuse m agn ification : m ost fluoro system s in crease th e radiation em itted × ≈ 4 to com - pen sate for th e associated reduct ion in im age brigh t n ess 4. “boost” m ode can double th e radiation output. Use sh ould be kept to a m in im um 5. use live fluoro on ly w hen absolutely n ecessary 6. for lateral im aging, w h en possible stan d on th e “dow n stream ” (im age in ten sifier (Im I)) side of th e C-arm : scatter is th e m ost sign ifican t cause of exposure h ere an d is h igh er on th e source side47 (th is asym m et r y is n ot as sign ifican t for C-spin e48) 7. keep th e Im I as close to th e pat ien t as possible (reduces patien t & sta exposure an d im proves im age qualit y) 8. on AP im ages (w ith th e patien t pron e or supin e): position th e x-ray tube under th e table w ith th e Im I over th e patien t (low ers scatter exposure to sta )49 9. collima te th e beam as m uch as possible: reduces radiation to patien t an d to sta , an d results in less im age degradation 10. keep hands, arm s, etc. out of th e prim ar y beam at all tim es (consider using leaded gloves if h an ds n eed to be w ith in th e beam or n earby for an exten ded tim e) 11. m in im ize n um ber of im ages: plan your sh ot, avoid frequen t “ch ecks” or peeks 12. use im age guided n avigation w h en possible an d pract ical 13. leaded glasses are recom m en ded on ly for person n el w ith ver y h igh fluoro tim es: cataracts can be in duced by sin gle doses of 200 rads (ver y h igh ), cum ulat ive doses of 750 rads h ave n ot been associated w ith cataracts

Table 12.5 Radiation exposure with fluoroscopy39a Plain Radiology and Contrast Agents 225 Distance from beam Typical t eam m em ber Deep exposure Superficial e xp o su r e feet m et ers (m rem /m in) Direct beam p a t ie n t 4000 20 29 1 0.3 surgeon 6 10 0 ≤2 2 0.6 assistant 0b 0 b 3 0.9 scrub tech 5 1.5 anesthesiologist ain a m ock OR set up for maxim al scatter bafter 10 minutes of exposure Table 12.6 Annual occupational radiation dose limits Recom m ended MAXIMAL dose (rem /yr) Target organ 5 whole body 15 lens of eye 50 skin, hands, feet 15 other organs (including thyroid) Re fe r e n ce s th e prever tebral soft t issues on m ult idetector CT. 12 AJNR Am J Neuroradiol. 2009; 30:136–141 [1] Sp en ce KF, Decker S, Sell KW . Bu rstin g Atlan tal [12] DeBen h e K, Havel C. Utilit y of Prevertebral Soft Tis- Fracture Associated w ith Rupture of th e Tran sverse sue Measurem en ts in Iden t ifyin g Patients w ith Cer- Ligam en t . J Bon e Join t Su rg. 1970; 52A:543–549 vical Sp in e Inju r y. An n Em erg Med. 1994; 24:1119– 1124 [2] Field in g JW , Coch ran GB, Law sin g JF, III, Hoh l M. [13] Miles KA, Fin lay D. Is Prever tebral Soft Tissu e Sw el- Tears of th e t ransverse ligam en t of th e atlas. A clin - lin g a Usefu l Sign in In ju ry of th e Cer vical Spin e? ical an d biom ech an ical st ud y. J Bon e Join t Su rg Am . Injur y. 1988; 19:177–179 1974; 56:1683–1691 [14] Naid ich JB, Naid ich TP, Garfein C, et al. Th e W iden ed [3] Heller JG, Viroslav S, Hu dson T. Je erson fract ures: In terspinou s Distan ce: A Usefu l Sign of An terior th e role of m agn ification artifact in assessin g t ran s- Cer vical Dislocation . Rad iology. 1977; 123:113–116 verse ligam en t in tegrit y. J Spin al Disord. 1993; 6:392–396 [15] Bailey DK. Th e Norm al Cer vical Spin e in In fan ts an d Ch ildren . Rad iology. 1952; 59:712–719 [4] Hin ck VC, Hop kin s CE. Measurem en t of th e Atlan to- Den tal In terval in th e Ad u lt. Am J Roen tgen ol Radi- [16] Yogan an d an N, Pin tar FA, Lew SM, Rao RD, Ran gara- um Th er Nucl Med. 1960; 84:945–951 jan N. Quan titative An alyses of Pediatric Cer vical Spin e Ossification Patterns Usin g Com puted Tom og- [5] Meijers KAE, van Beu sekom GT, Lu yen d ijk W , et al. raph y. An n Adv Au tom ot Med . 2011; 55:159–168 Dislocation of th e Cer vical Spin e w ith Cord Com - pression in Rh eum atoid Arth rit is. J Bon e Join t Surg. [17] Fisch er FJ, Van dem ark RE. Sagittal cleft (butterfly) 1974; 56B:668–680 vertebra. J Bon e Join t Surg. 1945; 27:695–698 [6] Panjabi MM, Od a T, Crisco JJ, III, Oxlan d TR, Katz L, [18] Popp el MH, Jacobson HG, Du BK, Gottlieb C. Basilar Nolte LP. Exp erim en tal st u dy of atlas in ju ries. I. Bio- im p ression an d plat ybasia in Paget's d isease. Br J m echan ical an alysis of th eir m echan ism s an d frac- Radiol. 1953; 21:171–181 t u re p attern s. Spin e. 1991; 16:S460–S465 [19] Koen igsberg RA, Vakil N, Hon g TA, Htaik T, Faerber [7] Powers B, Miller MD, Kram er RS, et al. Trau m atic E, Maiorano T, Dua M, Faro S, Gon zales C. Evaluation Anterior Atlanto-Occipital Dislocation . Neurosur- of plat ybasia w ith MR im aging. AJNR Am J Neurora- ger y. 1979; 4:12–17 diol. 2005; 26:89–92 [8] Brockm eyer D. Dow n syn d rom e an d cran iover tebral [20] Goel A, Bh atjiw ale M, Desai K. Basilar in vagin ation : in stabilit y. Top ic review an d t reatm en t recom m en - a study based on 190 surgically treated patients. J dation s. Pediatr Neurosurg. 1999; 31:71–77 Neurosurg. 1998; 88:962–968 [9] Sch m id ek HH, Sw eet W H. Op erative Neu rosu rgical [21] McRae DL. Th e Significan ce of Abn orm alities of the Tech n iques. New York 1982 Cer vical Spin e. AJR. 1960; 70:23–46 [10] Epstein N, Epstein JA, Benjam in V, Ran soh o J. Trau- [22] Cron in CG, Loh an DG, Mh uirch eart igh JN, Meeh an m atic Myelopathy in Patien ts W ith Cer vical Spin al CP, Mu rp hy JM, Roch e C. MRI evalu ation an d m eas- Sten osis W ith out Fract ure or Dislocation : Methods of Diagn osis, Man agem en t , an d Progn osis. Spin e. urem en t of th e norm al od on toid p eg p osition . Clin 1980; 5:489–496 Rad iol. 2007; 62:897–903 [11] Rojas CA, Verm ess D, Ber tozzi JC, W h itlow J, Guidi C, Mar t in ez CR. Norm al thickn ess an d appearan ce of

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Im aging and Angiography 227 13 Im aging and Angiography 13.1 CATscan (AKA CTscan) 13.1.1 General inform at ion CAT scan s em ploy ion izin g radiation (x-rays) w ith th e atten dan t risks; see Radiation safety for n eu- rosurgeon s (p.223). Atten uation of th e x-ray beam on a CT scan is defin ed in Houn sfield un its. Th ese un its are n ot absolute, an d var y bet w een CT scan n er m odels. Som e sam ple values are sh ow n in Table 13.1. 13.1.2 Noncont rast vs. IV cont rast enhanced CTscan (CECT) Non con trast CT scan s are often em ployed in em ergency sit uat ion s (to quickly rule-out m ost acute abn orm alit ies), to evaluate bon e in great detail, or as a screen ing test . It excels in dem on stratin g acute blood (EDH, SDH, IPH, SAH), fract ures, foreign bodies, pn eum oceph alus an d hydroceph alus. It is w eak in dem on stratin g acute stroke (DW I MRI is preferred), an d often h as poor sign al qualit y in th e posterior fossa (due to bon e art ifact). IV en h an ced CT scan s are used prim arily for im aging n eoplasm s or vascular m alform ation s, espe- cially in patien ts w ith con train dication s to MRI. All CT con trast agen ts con tain iodin e. Typical IV dose of con trast: 60–65 m l of e.g. Isovue 300® (p.220) w h ich delivers 18–19.5 gram s of iodine. 13.1.3 CT angiography (CTA) Em ploys rapid inject ion of iodin ated con trast at 3–4 cc/sec, t ypically 65–75 m l of e.g. Isovue 300®. Optim al results in patien ts w h o can h old th eir breath for 30–40 secon ds (for spiral CT). Table 13.1 Hounsfield units for a sam ple CTscanner Definit ions Hounsfield unit s Com m ent d e fin it io n no attenuation (air) –1000 d e fin it io n 13 d e fin it io n water 0 acute SDH or EDH, fresh SAH dense bone + 1000 disc densit y is ≈ 2 × thecal sac Cranial CT brain (grey m atter) 30 to 40 brain (white m atter) 20 to 35 cerebral edema 10 to 14 CSF + 5 bone + 600 blood clota 75 to 80 fat –35 to –40 calcium 100 to 300 enhanced vessels 90–100 Spine CT 55–70 disc m aterial thecal sac 20–30 aHct < 23% will cause an acute SDH to be isodense with brain

228 Im aging and Diagnostics Various m eth ods m ay be used to determ in e tim in g of CT after inject ion : m ay be based on t im e to peak in aorta after a sm all test inject ion , or can be based em pirically on tim e, or give injection an d look for peak in th e region of in terest. Accuracy is dim in ish ed for vessels th at are perpen dicular to th e axial CT plan e. Also in th e vicin ity of den se clot, CTA h as trouble resolving th e adjacen t vessels. 13.1.4 CT perfusion (CTP) Requires use of iodin ated con trast. Areas of in terest are selected from an un en h an ced CT scan in th e 3 supraten torial vascular territories. Con trast is given at a stan dard rate (e.g. 40 m l IV at 5 m l/sec). Scan s th rough th e region s of in terest are repeated at in tervals, e.g. ever y 2 secon ds for 1 m in ute. Acetazolam ide (ACZ) (Diam ox®) ch allenge: after th e above, a bolus of 1000 m g of IV ACZ is given , an d scan s are repeated at in tervals for approxim ately 10 m in utes, w ith a fin al scan usually at 15 m in utes. Param eters th en calculated from th e im ages: cerebral blood volum e (CBV), CBF, m ean t t ran sit t im es (MTT), an d t im e to peak (TTP). In isch em ic st roke, MTT is alm ost alw ays in creased an d CBF is decreased. Abn orm alities th at can be dem on strated: 1. flow sign ifican t sten osis: decreased CBV & CBF, in creased MTT an d TTP 2. steal: after ACZ ch allen ge (see above), CBV & CBF decrease, often w ith in creases in th e corre- spon din g con tralateral territor y; MTT in creases In com parison to perfusion w eigh ted MRI (PW I) (p.232): 1. PW I acquires m ultiple slices of th e w h ole brain over an d over. CTP is lim ited to a given slice or several slices (usually 10–20 m m thick), and one has to ch oose w here to place th at slice 2. PW I h as m ore art ifact th an CTP 13.2 Magnet ic resonance im aging (MRI) 13.2.1 General inform at ion Defin ition s1 Abbreviation s: ● TR: tim e to repet it ion 13 ● TE: tim e to ech o ● TI: tim e to inversion ● T1: spin -lattice relaxat ion tim e (“tim e to m agn etize”) (regrow th ) ● T2: spin -spin relaxation tim e (“t im e to dem agn etize”) (decay) 13.2.2 T1 w eight ed im age (T1WI) Sh ort T1 → h igh sign al (brigh t). “An atom ic im age”, som ew hat resem bles CT. Sh orter acquisition t im e th an T2WI. Proton rich t issue (e.g. H2O) h as lon g T1. Table 13.2 Range of acquisition data short TE long TE (te < 50) (te > 80) short TR T1WI (TR< 1000) T2WI long TR proton density or spin densit y (TR> 2000) Table 13.3 T1WI, MRI intensit y change fat (including bone m arrow), whit e m at t er grey matter ca lciu m CSF, blood > 48 hrs old, m elanin bone (note: grey-bar illustrates direction of intensit y change and does not show actual grey on MRI)

Im aging and Angiography 229 Clues to recogn izin g T1W I: CSF is black, subcutan eous fat is w h ite, TR an d TE are sh ort (h un dreds an d double digits, respectively). Th e on ly objects th at appear w h ite on T1W I are: fat, m elan in , On yx® (p.1589), an d subacute blood (> 48 h rs old). W h ite m atter is h igh er sign al th an grey m atter (m yelin h as a h igh fat con ten t). Most path ology is low sign al on T1W I. 13.2.3 T2 w eight ed im age (T2WI) Lon g T2 → h igh sign al (brigh t). “Path ological im age.” Most path ology sh ow s up as h igh sign al, in clud- ing surrounding edem a. Clues to recogn izin g T2WI: CSF is w h ite, TR & TE are lon g (th ousan ds an d h un dreds, respect ively). 13.2.4 Spin densit y im age AKA balan ced im age, AKA proton den sit y im age. Part w ay bet w een T1W I an d T2W I. CSF = grey, approxim ately isoden se w ith brain . Becom in g less com m on ly used. 13.2.5 FLAIR 13 Acronym : FLuid-Atten uated Inversion Recover y. Long TR an d TE. Resem bles a T2W I except th e CSF is n ulled out (appears dark). Th e grey/w hite in ten sit y pattern is reversed from T1W I an d is m ore prom in ent. Most abn orm alities including MS plaques, other w hite m atter lesions, tum ors, edem a, en ceph alom alacia, gliosis an d acute in farcts appear brigh t. Periven tricular lesion s such as MS plaques becom e m ore con spicuous. Also good for dem on stratin g abn orm alit ies in CSF. Di eren tial diagn osis of in creased sign al in subarachn oid spaces on FLAIR: 1. subarach noid h em orrh age (SAH): th e best sequen ce for detect in g acute SAH on MRI 2. m eningitis: occurs in som e cases 3. m eningeal carcinom atosis 4. superior sagittal sinus throm bosis 5. stroke 6. adjacen t tum or: ? if related to h igh er protein 7. previous adm inistration of gadolin ium 8. h igh levels of FIO2 especially at levels n earin g 100%as m ay be used in patien ts gett in g MRI un der gen eral an esth esia.2 Sh ow s up in basal cistern s an d in sulci over th e convexity, but n ot in ven tricles 13.2.6 Echo t rain (AKA fast spin echo (FSE)) t r is h eld con stan t, te is progressively in creased utilizing m ultiple ech oes (8–16) rath er th an on e. Im age approach es T2W I but w ith substan t ially reduced acquisition t im e (fat is brigh ter on FSE, w h ich m ay be rect ified by fat suppression tech n iques). 13.2.7 Gradient echo AKA T2* (called T2-star), an d som e m an ufact urers h ave t radem arked n am es for th is, e.g. “GRASS” (a GE t radem arked acronym for Gradien t Recalled Acquisition in a Steady State) or FISP. A “fast” T2W I utilizing a par t ial flip an gle. CSF an d flow in g vessels appear w h ite. Bon e, calcium an d h eavy m etals are da rk. Typical acquisition data: TR = 22, TE = 11, an gle 8°. Used e.g. in cer vical spin e to produce a “m yelograph ic” im age, im proves MRI’s abilit y to delin eate bony spurs. Also sh ow s sm all old cerebral h em orrh ages (seen in 60% of patien ts presen t ing w ith h em orrh agic in farct ion , an d in 18% w ith isch em ic in farcts3); th ese pat ien ts m ay be at in creased risk of h em orrh age from an ticoagulation . Gra dient-echo T2WI MRI is th e 3–4 × m ore sen sitive test th an FLAIR for dem on stratin g in t raparen - chym al blood (w h ich appears da rk) due to h igh sen sitivit y to param agn etic ar tifact. It is n ot as sen si- t ive as th e m ore recen tly in t roduced SW I. Table 13.4 T1WI, MRI intensity change brain edem a/wat er CSF grey m at t er white bone, fat matter (note: grey-bar illustrates direction of intensit y change and does not show actual grey level on MRI)

230 Im aging and Diagnostics 13.2.8 “STIR” im age Acronym for “Sh ort Tau Inversion Recover y.” Sum m ates T1 & T2 sign als. Causes fat to drop out – som etim es also called fat suppression or “fat sat” (for fat saturation ), allow s gadolin ium en h an ce- m en t to sh ow up better in areas of fat. Useful prim arily in spin e an d orbit. Ver y good for sh ow in g bon e edem a (can h elp in dat in g spin e fract ures). Th e dorsal root ganglion m ay en h an ce on fat sup - pression im ages. 13.2.9 Cont raindicat ions t o MRI General inform at ion An exten sive referen ce4 details safety issues. Web sites for MRI safety in clude: ww w.MRIsa fety.com an d www.IMRSER.org . Som e issues th at com e up frequen tly in n eurosurgical patien ts follow s. Pregnancy and MRI Durin g th e first trim ester, MRI can cause reabsorpt ion of products of con ception (m iscarriage). Th ere are n o st udies to determ in e th e lon g term e ect s of MRI on a fetus after th e first trim ester (th e low risk of MRI in th is situation is probably preferable to th e kn ow n dan gers of ion izin g radiation of x- rays (in cludin g CT)5). Gadolin ium con trast is con train dicated durin g all of pregn an cy, an d is n ot approved for use in age < 2 years. Breast-feeding m ust be in terrupted for 2 days after adm in istration of gadolin ium to th e m other. Com m on contraindicat ions t o MRI 1. cardiac pacem akers/defibrillator, im plan ted n eurostim ulators, coch lear im plan ts, in fusion pum ps: m ay cause tem porar y or perm an en t m alfun ction 2. ferrom agn et ic an eur ysm clips (see below ): som e cen ters exclude all patien ts w ith any t ype of aneurysm clip 3. m etallic im plan ts or foreign bodies w ith large com pon en t of iron or cobalt (m ay m ove in field, or may heat up) 4. Sw an n -Gan z cath eter (pulm on ar y arter y cath eter) 5. m etallic fragm en ts w ith in th e eye 6. placem en t of a vascular sten t, coil or filter w ith in th e past 6 w eeks 1 3 7. sh rapn el: BB’s (som e bullets are OK) 8. rela tive con train dication s: a) claustroph obic pat ien ts: m ay be able to sedate adequately to perform study b) crit ically ill patien ts: abilit y to m on itor an d access to pat ien t are im paired. Specially design ed n on -m agn etic ven t ilator m ay be required. Can n ot use m ost bran ds of elect ron ic IV pum ps/ r e gu lat o r s c) obese patien ts: m ay n ot physically fit in to m any closed bore MRI scan n ers. Open bore scan - ners m ay circum ven t th is but m any utilize low er field stren gth m agnets an d generally pro- duce in ferior qualit y im ages in large patien ts d) n on -MRI com patible m etal im plan ts in th e region of in terest (or previous surgery w ith h igh speed drills w h ich m ay leave m etal filin gs): m ay produce suscept ibilit y art ifact w h ich can dis- tort the im age in that area e) program m able sh un t valve (p. 418): m ost w ill tolerate up to a 3 T MRI w ith out perm an en t dam age, h ow ever, th e pressure sett in g m ay be altered an d th erefore sh ould be rech ecked after h avin g an MRI for any reason Aneurysm clips and MRI MRI con cern s in patien ts w ith a cerebral an eur ysm clip: of the 1. th e dan ger of th e MRI m agn etic field causin g th e an eur ysm clip to be pulled or torqued o aneurysm or to tear the neck 2. th e art ifact produced by th e m etal of th e clip in th e m agn et ic field 3. h eat gen erated in th e region of th e clip: n ot clin ically sign ifican t Th e m ore ferrom agnetic th e clip, th e larger th e force exerted on it by th e m agn etic field an d th e greater the im age distortion near the clip. Stain less steel (SS) is classified as m ar tensitic (ferrom agn etic) or austen it ic (n on -ferrom agn etic). Cobalt-based superalloys are n on -ferrom agn et ic an d in clude Elgiloy (Sugita clips), Phyn ox (Yasargil),

Im aging and Angiography 231 Table 13.5 Magnetic rem anence of aneurysm clips6 Magnet ic rem anence (no Clip Type of st eel unit s) MRI com patible: no martensitic SS 100 Drake DR 12 17–7PH 44 Heifet z martensitic SS 74 Mayfield EN-58J 64 Scoville MRI com patible: yes Elgiloy 0 Olivecrona gold plated 0 Su g it a Vari-Angle 1 Sugita with loop 316 0 McFadden Phynox 0 Yasargil 0 Yasargil 1 Yasargil (old) 0 silver clip an d Vari-An gle (McFadden ). Essen tially all m odern an eur ysm clips are MRI com patible, but pat ien ts 13 clipped before th e 1990s m ay h ave ferrom agn etic clips. Table 13.5 sh ow s th e m agn et ic rem an en ce of various clips w h ich is related to th eir ferrom ag- n etic propert ies. If in doubt at th e tim e of an eur ysm surger y, apply th e follow in g sim ple test: n on - ferrom agn et ic clips can n ot be lifted or dragged w ith a sm all m agn et. 13.2.10 Hem orrhage on MRI Because its sign al ch aracteristics ch ange w ith tim e (an d locat ion ), blood is on e of th e m ost com plex en tit ies to in terpret on MRI. A m n em on ic for th e ch anges in appearan ce of blood on MRI w ith t im e is sh ow n in Table 13.6. See also in t racerebral h em orrh age (p. 1330). Blood, h em osiderin an d calci- um are dark on GRASS im ages. FLAIR (p. 229) is th e best sequen ce for detect in g SAH on MRI (p.229). 13.2.11 MRI cont rast Curren t agen ts are m ostly based on gadolin ium (a rare earth m etal w h ich is param agn etic in solu- t ion s) in clude: gadopen tatate dim eglum in e (Magnevist®), gadodiam ide (Om n iscan ®), gadoverseta- m ide (OptiMARK®), gadoben ate dim eglum in e (MultiHan ce®) an d gadoteridol (ProHan ce®). Adverse react ion s: 1. an aphylact ic react ion s: rare (prevalen ce: 0.03–0.1%) 2. n eph rotoxicit y: in ciden ce is low er th an w ith iodin ated agen ts used w ith an giogram s or CT an d x- ray contrast 3. n eph rogen ic system ic fibrosis (NSF): a rare, but serious illn ess ch aracterized by fibrosis of skin , join ts an d oth er organ s, w h ich is associated w ith cer tain gadolin ium con tain in g agen ts given to patien ts w ith severe ren al failure (m ost w ere on dialysis). Gadolin ium is n ow relatively con tra- in dicated w ith a GFR of 30–60 m l/m in , an d is con train dicated w ith GFR < 30.7 Safest agen ts: Dot- arem , Gadovist an d ProHan ce.8 Con trast agen ts w ith a lin ear st ructure appear to be associated w ith a h igh er risk of NSF an d in clude: Om n iscan , Mult ih an ce, Magn evist an d OptiMARK. In patien ts w ith en d-stage ren al disease, th e risk is ≈ 2.4%per gadolin ium study9 4. gadolin ium allergy: use th e sam e allergy prep as for iodin e allergy (p. 221) 5. as of th e t im e of publication of th is book, th e FDA is investigat in g th e risk of accum ulation of gadolin ium in brain t issue after repeated MRI scan s using gadolin ium based con trast agen ts (GBCAs).10 In th e m ean tim e, th e FDA is recom m en din g th at h ealth -care profession als con sider

232 Im aging and Diagnostics Table 13.6 Variation of brain MRI signal characteristics of intraparenchym al blood over time Ph a se Approxim at e t im e aft er onset T1 MRI T2 MRI Mnem onica Hyp e ra cu t e 0-6 hrsb I B I be Acu t e 6-72 hrs I D iddy Early subacute 3-7 d B D biddy Late subacute 7-14 d B B baby Chronic > 2 weeks D D doodoo a Mnem onic: B (bright or hyperintense com pared to brain), D (dark or hypointense), I (isointense) b Som e authors consider up to about 24 hrs as hyperacute lim itin g th e use of GBCAs to sit uation s w h ere th e addit ion al in form ation provided by th e con - trast is absolutely necessary 6. see also issues related to pregnancy (p.230) 13.2.12 Magnet ic resonance angiography (MRA) Th ere are 2 w ays to obtain an MRA ● Gadolin ium en h an ced: usually for extracran ial vessels (e.g. carotids) ● Non con trast im ages usin g flow related en h an cem en t tech n iques (m ost com m on : 2D tim e of fligh t (2D TOF)). Usually for in tracran ial vessels. Anyth in g th at appears brigh t on T1W I w ill also sh ow up on MRA, but doesn’t n ecessarily represent blood flow. Th is in cludes fat an d fat-laden m acroph ages in an area of old stroke. Usin g fat-sat T1W I can m itigate th is. Has som e utilit y in screen ing for an eur ysm s (p. 1161), an d for an giograph ically occult vascular m alform at ion s (p.1246). High -flow AVMs are h ard to resolve because arterialized vein s can appear sim ilar to arteries. 13.2.13 Di usion-w eight ed im aging (DWI) and perfusion-im aging (PW I) 13 Di usion-w eighted im aging Prim ar y uses: early detect ion of isch em ia (stroke) an d di eren tiatin g act ive MS plaques from old on es. DW I is sen sitive to ran dom Brow n ian m otion of w ater m olecules. Tw o im ages are gen erated, an apparen t di usion coe cien t (ADC) m ap (based on a n um ber of variables (tim e, slice orien tation…)), an d a t race im age (th e actual DW I).11 Freely di using w ater (e. g. in CSF) appears dark on DWI. Th e DWI is based on a T2W I, an d anyth in g th at is brigh t on T2W I can also be brigh t on DWI (so- called “sh in e-th rough”). Sin ce brigh t areas on DW I can represen t eith er restricted d usion or T2 “sh in e-th rough .” ch eck th e ADC m ap: if th e area is black on th e ADC m ap, th en th is likely repre- sen ts t rue restricted di usion (recen t in farct is th e m ost com m on etiology). In traparen chym al areas of brigh t sign al on DW I th at are n ot brigh t on th e ADC m ap are abn or- m al and represent regions of restricted di usion such as acute stroke. Di eren tial diagn osis of areas of in creased sign al (brigh t) on DW I: 1. isch em ic brain : a cute st roke an d areas w ith hypoperfusion (pen um bra). W h ile restricted di u- sion usually in dicates irreversible cell injury (death ), it can som et im es indicate t issue th at is just n ear cell death (pen um bra). Acute brain isch em ia can ligh t up w ith in m inutes.12,11 Th e DW I abn orm alit y w ill persist for ≈ 1 m on th . Th e ADC m ap usually n orm alizes after ≈ 1 w eek 2. cerebral abscess (p. 323): DW I = brigh t , ADC = dark 3. a ct ive MS plaque (old plaques w ill n ot be brigh t) 4. som e t um ors: m ost t um ors are dark on DWI, but h igh ly cellular t um ors m ay h ave decreased dif- fusion (brigh t on DWI) (e.g. epiderm oids, som e m en in giom as…) Oth er possible uses of DWI: TIAs: som e, but n ot all,13 are associated w ith DWI abn orm alit ies. How ever, factors oth er th an focal isch em ia (e.g. global isch em ia, hypoglycem ia, status epilepticus…) can produce ADC declin e an d th e DWI im ages m ust th erefore be in terpreted in relation to th e clin ical sett in g.11 DWI m ay also be able to distin guish cytotoxic from vasogen ic edem a (p. 90).14,15

Im aging and Angiography 233 Perfusion-w eight ed MRI Provides in form at ion related to th e perfusion status of th e m icrocirculation . PW I is th e m ost sen sit- vie study for isch em ia of th e brain (m ore sen sitive th an DW I an d FLAIR w h ich prim ar ily sh ow infa rcted t issue). Th ere are several m eth ods curren tly in use; th e bolus-con trast approach is th e m ost w idely em ployed.11 Ultrafast gradien t im agin g is used to follow th e gradual reduct ion to n orm al fol- low in g adm in istration of con trast (usually gadolin ium ). A sign al w ash -out cur ve is derived an d is com pared to con trast in an arter y. In pract ical term s, PW I is n ot w idely used because of tech n ical ch allenges. Tim e-to-peak an d m ean -tran sit-tim e are 2 com m on param eters th at are displayed (h igh - er sign al = lon ger tim es beyon d n orm al). DWI and PWI m ism at ch DW I an d PW I m ay be com bined to locate areas of di usion -perfusion m ism atch (deficit on PW I th at exceeds th e zon e of di usion deficit on DW I), th us iden tifyin g salvageable brain tissue at risk of in farction – “pen um bra” (p. 1202) – e.g. to screen for poten tial can didates for th rom bolyt ic th erapy.16 13.2.14 Magnet ic resonance spect roscopy (MRS) General inform at ion Th is sect ion specifically covers proton (H +) MRS w h ich can be perform ed on alm ost any MRI scan n er (especially un its ≥ 1.5 T) w ith th e appropriate soft w are. Spect roscopy of oth er n uclei (e.g. ph osph o- rous) can be evaluated on ly w ith specialized equipm en t . Single voxel MRS General inform ation A sm all area is selected on th e “scout” MRI an d th e spectroscopic peaks for th at region are displayed in reson an ce as a fun ct ion of par ts-per-m illion (ppm ). Sin ce on ly sm all region s are selected, m ay be subject to “sam plin g” error. Clin ically im portan t ch aracteristic peaks are delin eated in Table 13.7. Table 13.7 Im portant peaks on proton MRS 13 Moiet y Re so n a n ce Descript ion (ppm ) lipid 0.5–1.5 slightly overlaps lactate peak at TE ≈ 35 la ct a t e 1.3 a couplet peak. Not present in norm al brain. End product of anaerobic glycolysis, a m arker of hypoxia. Present in: N-acetyl aspartate 2 ischem ia, infection, demyelinating disease, inborn errors (NAA) of m etabolism… At higher TE (e.g. TE= 144), the peak inverts which can help distinguish it from the lipid peak cre at in e 3a (Cr) 3.2 a neuronal marker. Norm ally the tallest peak (higher than Cr or Cho). choline ↓ in ≈ all focal and regional brain abnormalities (tum or, (Cho) MS, epilepsy, Alzheim er’s disease, abscess, brain injury…) useful primarily as a reference for choline. Higher in grey matter than white matter marker of mem brane synthesis. ↑ in neoplasms and som e rare conditions of increased cell growth & in the developing brain. Stroke is low in choline aCr has another less im portant peak

234 Im aging and Diagnostics NAA Re s o n a n c e choline 80 choline Cr Cr NAA la cta te 60 lipid 40 20 0 -20 -40 PPM PPM 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Fig. 13.1 Proton MRS of (A) norm al brain, and (B) high grade glioma Illustrative pat terns Norm al brain : See Fig. 13.1. Tum or: See Fig. 13.1. ↓ NAA, ↑ lact ate, ↑ lipid, ↑ ch olin e (ru le of th um b: w ith gliom as, th e h igh er th e ch olin e, th e h igh er th e grade up to grade 3, th ereafter n ecrosis reduces relative ch olin e levels and the lipid peak m ay be utilized). St roke:↑ lact ate peak predom in ates. Ch olin e is ch aracteristically low. Abscess17: Reduced NAA, Cr & ch olin e peaks, an d “atypical peaks” (succin ate, acetate…) from bac- terial syn th esis is path ogn om on ic for abscess (n ot alw ays present). Lactate m ay be elevated. Mu lt ip le scler osis: Blan d pattern . NAA sligh tly reduced. Lactate an d lipid sligh tly elevated. Ch ol- ine not elevated. Possible uses of MRS 1. di eren tiatin g abscess from n eoplasm 2. post-op enhancem ent vs. recurrence of tum or 1 3 3. distinguish in g tum or from MS plaques: occasion ally can n ot be di eren tiated 4. in AIDS: m ay be able to h elp di eren tiate toxo from lym ph om a from PML (PML: ↓ NAA, n o sig- nificant increase in cholin e, lactate or lipid) 5. th e prom ise of di eren tiatin g t um or in filtration from edem a h as n ot m aterialized 6. som e ut ilit y in dist in guish in g tum or from radiation n ecrosis (p. 1560) 7. large in ositol peak m ay dist in guish h em angiopericytom a from m en ingiom a18) Mult i-voxel MRS Color coded scan w ith selected overlay for NAA, ch olin e… on e at a t im e. May reduce risk of sam plin g error. 13.2.15 Di usion t ensor im aging (DTI) MRI and w hit e m at t er t ract s AKA di usion ten sor tractography (DTT) MRI. An MRI tech n ique th at dem on strates white ma tter t ra cts by exploit in g th e di eren ce in di usion parallel to th e n er ve axon s th at com prise w h ite m atter t racts from di usion perpen dicular to th eir course. Available on ly w ith specialized soft w are for specific MRI scan n ers. Con train dication s are sam e as for MRI in gen eral (p. 230). Probably m ost useful to perm it plan n ing surgical approach es th at m in im ize disruption of critical w h ite m atter t racts durin g in traparen chym al brain surger y for deep lesion s, especially w h en a lesion (e.g. tum or, AVM, cerebral h em orrh age…) m ay displace th ese t racts from th eir expected position . Th e m ajor division s of w h ite m atter t ract s dem on strable by DTT MRI are ( Fig. 13.2): ● Projection fibers: ten d to be orien ted rostro-caudally ○ Corticospin al tract coalesces as coron a radiata fun n els in to in tern al capsule an d form s pyram i- dal tract

Im aging and Angiography 235 Short U Fib ers Superior Longitudinal Fasciculus CinguluCmorpus Callosum AC PC Uncinate Inferior Longitudinal Fasciculus sulucics F a Fig. 13.2 White m atter tracts (color conventions for DTI are not used in this anatom ic diagram) ● Com m isural fibers: m edio-laterally orien ted, con n ecting th e cerebral h em isph eres 13 ○ Corpus callosum ○ An terior com m isure ○ Posterior com m isure ● Association fibers: con n ect region s w ith in th e sam e h em isph ere ○ U-fibers: con n ect adjacen t gyri ○ Lon g association fibers: con n ect m ore distan t areas – Optic radiation s: con n ect lateral gen iculate bodies to visual cortex. Pass lateral to th e body of the lateral ventricles. – Un cin ate fasciculus: con n ects th e an terior tem poral lobe to th e in ferior fron tal gyrus. Dam age can cause language deficits. – Superior lon git udin al fasciculus (SLF): con n ects region s of fron tal lobe to tem poral an d occi- pital lobes. Injur y can cause lan guage deficits. – Arcuate fasciculus: part of SLF. Classic n euroan atom y teach ing: con n ects th e superior an d m iddle fron tal gyri (Broca’s area (m otor speech )) to th e superior tem poral gyrus (Wern icke’s area (lan guage com preh en sion )). DTI h as suggested broader con n ection s, in cludin g prem otor cortex. Injur y causes con duction aph asia – In ferior lon gitudin al fasciculus (ILF): con n ects tem poral an d occipital lobes at th e level of th e optic radiation . Injur y can cause deficits in object recogn ition , visual agn osias, prosopagn osia (face blin dn ess) – Cin gulum : project from cin gulate gyrus to th e en torh in al cortex as part of th e lim bic system Th e conven tion for color coding tracts on DTI im ages19: ● Blue: superior-in ferior t ract s ● Red: m ediolateral (h orizon tal) t ract s ● Green : an terior-posterior t racts Ow in g to a n um ber of tech n ical con sideration s, DTI is som ew hat m ore operator- depen den t th an conven tion al MRI. For surgical plan n in g, th e goal is to keep th e surgical t rajector y rough ly parallel (at < 30°angle) to the long axis of th e w hite m atter tract that one is tr ying to preser ve (unproven hypothesis20). Surgical “corridors” h ave been described takin g in to con sideration preser vation of w h ite m atter t r a ct s: ● An terior corridor: parallel to association fibers, betw een th e SLF an d th e cin gulum ● Posterior corridor: en ters at th e parieto-occipital sulcus, passes adjacen t to th e opt ic radiation s ● Lateral corridor

236 Im aging and Diagnostics 13.3 Angiography See En dovascular Neurosurgery sect ion (p. 1575). 13.4 Myelography Con train dication s: 1. anticoagulation 2. allergy to iodin ated con trast: requires iodin e allergy prep (p. 221). NB: risk of adverse reaction still persists 3. in fect ion at th e desired pun ct ure site 4. exten sive m idlin e lum bar spinal fusion m ay preclude needle access to the subarachnoid space Lu m bar m yelogr am Usin g ioh exol (Om n ipaque® 140 or 180) as sh ow n in Table 12.4. Cer vical m yelogram w it h w ater solu ble con t r ast via LP Use ioh exol (Om n ipaque® 300 or 240) as sh ow n in Table 12.4. In ser t spin al n eedle in to lum bar subarach noid space, t ilt th e h ead of th e m yelogram table dow n w ith th e pat ien t’s n eck exten ded an d th en inject dye. If a com plete cer vical block is seen , h ave patien t flex n eck. If th e block can n ot be t raversed, patien t m ay n eed C1–2 pun ct ure or MRI (first obtain a CT w h ich m ay sh ow dye above th e block th at can n ot be appreciated on m yelography alon e). Post m yelogra p h ic CT In creases sen sitivit y an d specificit y of m yelography (p.1031). In cases of com plete block on m ye- logram , CT w ill often sh ow dye distal to th e apparen t site of th e block. 13.5 Radionuclide scanning 13.5.1 Three phase bone scan Techn etium -99 (99m Tc) pertech n etate is a radioisotope th at m ay be attach ed to various substrates for use in bon e scan n ing. It m ay be used to label polyph osph ate (rarely used today), diph osph on ate21 (MDP), or ph osph orous (HDP) (th e m ost w idely agen t used curren tly). Accum ulates in areas of osteoblastic activity. W ith tech n etium 99m -HDP, im ages are obtain ed im m ediately after inject ion (flow ph ase), at 1 3 15 m in (blood poolin g) an d in 4 h ours (bon e im aging). Cellulitis sh ow s up as in creased activity in th e first 2 ph ases, an d th ere is litt le or di use in creased act ivit y in th e 3rd. Osteom yelitis causes increased uptake in all 3 phases. Used in evaluation of acute osteom yelitis w ith sen sitivit y an d specificit y of ≈ 95%each , an d is usu- ally positive w ith in 2–3 days. False positives can occur in con dition s involving in creased bon e t urn - over, e.g. fract ure, septic arth rit is, tum ors. False n egative can occur in cases w ith associated bon e in farction . Applicat ion s for bon e scan s in clude: 1. in fect ion a) osteomyelitis of the spine – vertebral osteomyelitis (p.355) – or skull b) discitis (p.356) 2. tumor a) spine m etastases (p.818) b) prim ar y bon e tum ors of th e spin e (p. 792) c) skull tum ors (p.775) 3. diseases involving abnorm al bone m etabolism a) Paget’s disease: of th e skull or spin e (p.1120) b) hyperostosis fron talis in tern a (p. 780) 4. craniosyn ostosis (p.252) 5. fract ures: spin e or sku ll 6. “low back problem s” (p. 1032): to h elp iden tify som e of th e above con dit ion s 13.5.2 Gallium scan Nuclear m edicin e scan w ith 67Ga citrate w h ich accum ulates in areas of in flam m ation an d som e m align an cies. Ut ilit y in n eurosurger y for: sarcoidosis (p.189), ch ron ic vertebral osteom yelitis; see alsocom parison to bone scan (p.355).

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238 Im aging and Diagnostics 14 Elect rodiagnost ics 14.1 Elect roencephalogram (EEG) 14.1.1 General inform at ion Th e prim ar y use of EEG is in th e diagn osis an d m an agem en t of seizure disorders. Non -convulsive use of EEG is essen tially lim ited to m on itoring for burst suppression (see below ) (e.g. in duced barbi- t urate com a) or for di eren tial diagn osis of di use en ceph alopathy, in cludin g: 1. di eren tiatin g psych ogen ic un respon siven ess from organ ic: a n orm al EEG in dicates eith er psy- ch iatric un respon siven ess or locked-in syn drom e 2. n on -convulsive status epilepticus (seizures): absen ce or com plex part ial status 3. subclin ical focal abn orm alit ies: e.g. PLEDs (see below ), focal slow in g… 4. specific pattern s diagn ostic for certain path ologies: e.g.: a) periodic lateralizin g epileptiform disch arges (PLEDs): m ay occur w ith any acute focal cerebral in sult (e.g. h erpes sim plex en ceph alitis (HSE), abscess, t um or, em bolic in farct): seen in 85%of cases of HSE (on set 2–5 d after presen tation ), if bilateral is ≈ diagn ostic of HSE b) subacute sclerosing pan en ceph alitis (SSPE) (path ogn om on ic pattern ): periodic h igh voltage w ith 4–15 secs separation w ith accom panying body jerks, n o ch ange w ith pain ful st im ulat ion (di eren tial diagn osis in cludes PCP overdose) c) Creutzfeldt-Jakob disease (p.367): m yoclonic jerks. EEG → bilateral sh arp w ave 1.5–2 per sec- on d (early → slow in g; later→ triph asic). May resem ble PLEDs, but are react ive to pain ful sti- m ulat ion (m ost PLEDs are n ot) d) t riph asic w aves: n ot really specific. May be seen in h epatic en ceph alopathy, post-an oxia, an d hypon atrem ia 5. object ive m easure of severit y of en ceph alopathy: usually used for an oxic en ceph alopathy (e.g. periodic spikes w ith seizures in dicates < 5%ch an ce of n orm al n eurologic outcom e, w ith h igh m ortalit y). Alph a com a, burst suppression , an d elect rocerebral silen ce are all poor p r o gn o st ica t o r s 6. di eren tiatin g hydran en ceph aly (p. 288) from severe hydroceph alus 7. as a clinical confirm atory test in the determ ination of brain death (p.310) 14.1.2 Com m on EEG rhyt hm s. Com m on EEG rhyth m s are sh ow n in Table 14.1. 14 14.1.3 Burst suppression Isoelectric in tervals in terrupted by bursts of 8–12 Hz electrical act ivit y th at dim in ish to 1–4 Hz prior to electrical silen ce.1 Often used as an en dpoin t for t it ratin g n europrotect ive drugs such as barbitu- rates, propofol… 14.2 Evoked pot ent ials 14.2.1 General inform at ion Evoked poten tials are averaged EEG w aveform s recorded follow in g repetitive stim ulat ion . Th e proc- ess of averaging n ulls-out EEG act ivity th at is n ot tim e -locked to th e st im ulus. Resultan t w aveform s con tain peaks th at are n am ed N (n egative – upw ard deflection ) or P (positive – dow nw ard deflec- t ion ) follow ed by th e laten cy in m illisecon ds to th e on set of th e peak. Table 14.1 Com mon EEG rhythms Sym bol Fr e q u e n cy Rh yt h m Δ 0–3 Hz d e lt a θ 4–7 Hz theta α 8–13 Hz a lp h a β > 13 Hz beta

Electrodiagnostics 239 14.2.2 Sensory evoked pot ent ials (SEP) General inform at ion May use elect rical st im ulat ion of periph eral n er ves (som atosen sor y or (SSEP)), auditor y clicks th rough earph on es (auditor y or AEP, AKA BAER (brain stem auditor y evoked respon se)) or flash in g ligh ts th rough goggles (visual EP or VEP). Evoked poten tials are m ost com m on ly used by n eurosurgeon s for in traoperative m on itoring pur- poses. SSEP (especially from m edian n er ve st im ulation ) also h as progn ostic sign ifican ce in cer vical spon dylotic m yelopathy2 alth ough use for th is purp ose is lim ited. Typical w aveform s Ab b re via t io n s Abbreviation s used below : BAER = brain stem auditor y evoked respon se; UE/LE SSEP = upper/low er extrem it y som atosen sor y evoked poten tial; PR VER = pat tern reversal visual evoked respon se w h ich requires patien t cooperat ion an d visual atten t ion as opposed to flash VER w h ich m ay even be don e th rough closed eyelids. See also referen ces.3,4 14.2.3 Int ra-operat ive evoked pot ent ials General inform at ion EPs m ay be used for intra-operative m onitoring (e.g. m onitoring hearing during resection of vestibular schw ann om as, or m onitoring SSEPs during som e spine surgery), however, their delayed nature often m akes them of lim ited usefulness in avoiding acute intra-operative injury. A 10%increased latency of Table 14.2 Typical stim ulus values for intra-op evoked potentials Com m ent Test St im ulus Freq (Hz) Durat ion Magnit ude (m cS) BAER 23.5 150 85–100 dB rarefaction usually better than com- pression UE SSEP 4.7 300–700 up to 50 mA supram axim al stimulus (sensory (median nerve at wrist) threshold + motor threshold) 14 LE SSEP 4.7 300–700 up to 100 m A supram aximal stimulus (posterior tibial at ankle) PR VER 1.97 16 × 16 checks, 1.6 cm each, at 1 m eter (subtends 55\" arc visual angle) Table 14.3 Input characteristics for acquiring evoked potentials Elect rode derivat ions Test Analysis M1a-CZZ, M2*-CZ, ground = FZ Input filt er Sensit ive Durat ion Re p s FZ-Erb’s point, CV7-FPZ, C3-FPZ, C3’-NC (Hz) (m cV) (m S) (non-cephalic, e.g. shoulder) popliteal fossa (front to back), CZ-FPZ, BAER 150–3000 25 15 1500 back (L5-T12) (difficult in obese or elderly), CI-CC (optional: som atosen- UE SSEP 30–3000 50 55–60 600 sory ipsilateral to contralateral) O1-A1, OZ-A1, O2-A1, OZ-CZ LE SSEP 30–3000 50 60 600 PR VER 5–100 50 500 100 aM= mastoid (“i” is ipsilateral to stim ulus, and “c” is contralateral)

240 Im aging and Diagnostics a m ajor EP peak, or a drop in am plitude of ≥ 50%is significan t and should cause the surgeon to assess all variables (retractors, instrum ents, blood pressure…). Intra-operative SSEPs m ay also be used to localize prim ary sensory cortex in anesth etized patients (as opposed to using brain m apping techni- ques in awake patients) by looking for phase reversal potentialsacross the central sulcus.5,6 Brainst em audit ory evoked responses (BAER) AKA auditory brainstem response (ABR), AKA auditory evoked poten tial (AEP). Auditory clicks are delivered to the patient by earphones. Peaks Table 14.4). Once used for assistance in diagnosing ves- tibular schwann om as, their use for intraoperative m onitoring is lim ited and has been largely replaced by direct eighth cranial n erve m onitoring w hich provides m ore rapid inform ation for th e surgeon . SSEP m onit oring during spine surgery Paralytics act ually im prove SSEP recordings by reducin g m uscle art ifact, but w ill abolish th e visible t w itch th at con firm s th at th e st im ulus is bein g received. Typical stim ulus sites: m edian , uln ar, an d t ibial n er ves. Im pulses ascen d in th e ipsila tera l posterior colum n . UE SSEPs travel prim arily in th e dorsal colum n s, but LE SSEPs are carried m ostly in th e dor- solateral fasciculus (p. 72) w h ich is supplied by th e a nter ior spin al artery. Th us, UE an d LE SSEPs are m ore sen sitive to direct m ech an ical e ect s prim arily on th e posterior spin al cord (sen sor y) an d m ay rem ain un ch anged w ith som e injuries to th e an terior cord (m otor), h ow ever, LE SSEPs can detect isch em ic e ect s on th e an terior cord by vir t ue of involvem en t of th e an terior spin al artery. In a person al series of 809 pat ien ts,7 17 h ad SSEP degradation , 14 of th ese (82%) respon ded to in t ra-op in ter ven tion s (see below ), an d in 13 of th ese 14 (93%) th ere w ere n o n ew deficits. In th e 3 th at did n ot respon d, 2 h ad sign ifican t n ew n eurologic deficits. Table 14.4 Evoked potential waveform s (note: values may di er from lab to lab) Test Figure Possible generators BAER CM P3 P4 P5 CM cochlear m icrophonic P1 P2 P11distal VIII nerve, P7 P2 2proxim al VIII or cochlear nucleus, Mi-CZ P3 3lower pons (? superior olivary com plex), P44mid-upper pons, 0.25 uV P6 P55upper pons or inferior colliculus 10 mS 14 UE SSEP P22 N99(on FZ-EPP where EP is Erb’s point) AKA EP: LE SSEP entry of volley into distal brachial plexus, PR VER C3'-FPz N19 P22 early N1111(on CV7-FPZ): root entry zone (cervical Cv7-FPz N13/ P13 region), N1313cervicom edullary junction (recorded from N11 2 uV C2), EP N1919prim ary sensory cortex, P2222(early) m otor cortex, Fz-Ep P2222(late) IPSP “reaction” to N1818 10 mS P222(on L5-T12): lum bo-sacral plexus, P404(on CZ-FPZ): sensory cortex (analogous to N18 Cv7-FPz N25 N27 0.25 uV in UE SSEP, reversed in polarity for ? reason), Cz-FPz P40 N50 N272(on CV7-FPZ): ? dorsal colum n nucleus L5-T12 N3030 N30 P22 P100 striate & pre-striate occipital cortex, with contributions from thalamocortical volleys 50 mS P100 Oz-Cz 5 uV 500 mS

Electrodiagnostics 241 Table 14.5 Norm al values for evoked potentialsa (note: values m ay di er from lab to lab) Te st Param eters m eas- – – Norm al values – – Com m ent ured Me a n + 2.5 std dev BAER I-V peak latency 4.01 mS 4.63 mS I-III peak latency 2.15 mS 2.66 mS prolongation suggests lesion bet ween pons & colliculus, often vestibular sch wan no m a V absolute latency 5.7 m S 6.27 mS III-V peak latency prolongation suggests lesion bet ween lower pons & m idbrain, may be seen in M.S. UE SSEP N99-N1818 peak 9.38 mS 11.35 mS la t e n c y LE SSEP P2222-P4040 peak 15.62 mS 20.82 mS la t e n c y P4040 absolute 37.20 mS 44.16 mS la t e n c y PR VER P10010 absolute + 3 S.D. la t e n c y P100 inter-eye differ- 8–10 mS Inter-eye difference is more sensitive ence with full field stimulation. Monocular defect suggests conduction defect in that optic nerve anterior to chiasm (e.g. M.S., glaucoma, com pression retinal degeneration). Bilateral defect does not localize. anormal values in boldface are critical values used as cutoff for abnorm al results Transcranial m ot or evoked pot ent ials (TCMEPs) 14 An est h et ic requ ir em en t s: In addition to EP an esth etic requirem en ts, n eurom uscular blockade m ust be m inim ized to perm it ≥ 2 out of 4 t w itches. AKA m otor evoked poten tials (MEP): tran scran ial elect rical or m agn etic st im ulation of m otor cor- tex an d descen din g m otor axon s w ith recordin g of m otor poten tials from distal spinal cord or m uscle groups. Usin g direct elect rical st im ulation is lim ited in aw ake patien ts by local pain . Due to th e large poten tials, th e acquisition t im e is sh orter an d feedback to th e surgeon is alm ost im m ediate. How - ever, due to patien t m ovem en t from th e m uscle con tract ion s, con tin uous recording is usually n ot possible (except w ith m on itoring th e respon se over th e spin al cord). Useful for surger y involving th e spinal cord (cervical or th oracic), n o ut ilit y for lum bar spin e surgery.Seizures occur rarely, usually in patien ts w ith in creased seizure risk an d w ith h igh -rate stim ulat ion frequen cy. Con train dication s to MEP: 1. history of epilepsy/seizures 2. past surgical skull defects 3. m etal in head or neck 4. use special care w ith im plan ted elect ron ic devices Descending evoked pot entials (DEP) (Form erly referred to by th e m isleading term “n eurogen ic m otor evoked poten tials”). Rost ral stim u- lation of th e spin al cord w ith recording of a caudal n eurogen ic respon se from th e spinal cord or periph eral n er ve, or a m yogen ic respon se from a distal m uscle. DEPs can be m ediated prim arily by sen sor y n er ves an d th erefore do n ot represen t t rue m otor poten tials. How ever, sh ow n to be sen si- t ive to spinal cord ch anges an d m ay be useful w h en TCMEPs can n ot be obtain ed.

242 Im aging and Diagnostics 14.2.4 Elect rophysiologic m onit oring crit eria t o t rigger not ificat ion of surgeon Any of th e follow in g: 1. SSEP: a) 50%decrease in peak sign al am plitu de from baselin e b) increase in peak laten cy > 10% c) com plete loss of a w aveform 2. TCMEP: sustain ed 50%decrease in sign al am plitude 3. DEP: decrease in sign al of > 60% Int ervent ions for loss or degradat ion of m onit oring signal during spine surgery W h en com pression is th e culprit , th e progn osis m ay be good. Vascular injuries gen erally do n ot fare as w ell. Option s/suggest ion s in clude (adapted/excerpted from th e “Vitale ch eklist”8): 1. verify th at th e ch ange is real (check con n ection s, equipm en t…) 2. place OR on alert status a) an n oun ce in traoperative pause an d stop th e case b) elim in ate possible dist ract ion s (m usic, un n ecessar y conversation s…) c) “m uster th e t roops”: th e attendin g an esth esiologist, sen ior n eurologist or n europhysiologist an d experien ced n urse are called to th e room . Con sult a surgical colleague if n ecessar y 3. anesthetic/m etabolic considerations a) optim ize m ean arterial pressure (MAP usually > 85 m m Hg preferred) b) ch eck h em atocrit for an em ia (could con tribute to cord isch em ia) c) optim ize blood pH (ru le out acidem ia) an d pCO2 d) norm alize patient body tem perature e) ch eck an esth et ic tech n ical factors: assess exten t of paralytics f) discuss possibilit y of “Stagn ara w ake up test” (see below ) w ith atten din g an esthesiologist an d scrub nurse 4. technical/neurophysiologic considerations a) rule-out 60 Hz. in terferen ce from oth er equipm en t (OR table, C-arm , m icroscope… anyth in g w ith a plug) b) verify that stim ulating electrodes recording leads are m aking good contact 14.3 NCS/EMG 14 14.3.1 General inform at ion Elect rodiagn ostic studies of periph eral n er ves con sist of t w o parts: 1. con duction m easurem en ts: t ypically referred to as “NCV” (n er ve con duction velocit y) but tech n i- cally sh ould be called NCS (n er ve con duction st udies) sin ce am plitu de, laten cy an d duration of m otor & sensory nerves are also evaluated 2. elect rom yogram (EMG) AKA “n eedle exam ” (see below ) 14.3.2 Elect rom yography General inform at ion Th ere are 3 ph ases of an EMG exam : Phase 1 – in sertional activity: the elect ric response of the m uscle to m echanical irritation caused by sm all m ovem ents of th e needle Phase 2 – spontan eous activity: in m uscle at rest 1. norm al: silen t w ith stationary needle once insertional activit y h as subsided 2. spon tan eous act ivity: in depen den tly produced electrical act ivity. Usually abn orm al (alth ough som etim es seen in norm al volunteers). a) after den er vation (secon dar y to a n er ve injur y) or m uscle injur y: ● positive sh arp w aves (PSW ) ● fibrillation poten tials (AKA fibrillat ion s or fibs): act ion poten tials arisin g from single m uscle fibers. Detect able on EMG; n ot visible to th e n aked eye, c.f. fasciculat ion s (p. 505). Earliest on set 7–10 days after den er vation , som etim es n ot for 3–4 w eeks. If th e n er ve recovers, it

Electrodiagnostics 243 m ay rein n ervate th e m uscle, but w ith larger m otor un its resultin g in lon ger duration an d decreased num bers b) m yoton ic disch arges (“dive bom ber” soun d on speaker m on itor) c) com plex repetit ive disch arge (CRD): eph aptic con duction of groups of adjacen t m uscle fibers. Occurs in n europath ic or m yopath ic disorders d) fasciculation poten tials: n on specific, but t ypically associated w ith m otor n euron disease (ALS) (p . 1 8 3 ) e) other less com m on spon tan eous act ivity in cludes: m yokym ic, n eurom yton ic an d cram p disch arges Phase 3 – volitional activit y: evaluated w ith m inim al volitional e ort and m axim al e ort 1. m otor un it action poten tial (MUAP) an alysis: in cludes evaluation of m otor un it am plitu de, dura- tion , polyph asia an d stabilit y. Gen erally in crease am plitude an d duration suggest a disorder of th e LMN, an d reduct ion of am plitude an d duration suggests a prim ar y m yopath ic disorder 2. w ith m in im al volition al e ort . Tw o possible abn orm al fin din gs a) reduced recruit m en t (or fast firing) is always in dicative of a n europath ic process b) early or in creased recruit m en t: in dicat ive of a m yopath ic process 3. w ith m axim al e ort Definit ions 14 SNAP: sen sor y n er ve act ion poten tial. Key con cept: sin ce th e ganglion of th e sen sor y n er ves lies w ith in th e n eural foram en , pregan glion ic lesion s (injur y to th e n er ve root proxima l to th e n eural foram en , e.g. root com pression by h ern iated disc or root avulsion ) does n ot a ect th e cell body, an d th erefore th e distal SNAP is un a ected.9 Postganglion ic lesion s (distal to th e n eural foram en , e.g. periph eral n er ve injur y) reduces SNAP am plitu des an d/or slow s th e sen sor y con duction velocit y. F-wave: st im ulation of a n er ve causes orth odrom ic an d an tidrom ic con duct ion . Som e an terior h orn cells th at are stim ulated an tidrom ically w ill fire orth odrom ically producin g th e F-wave. F-w ave laten cy m ay be prolonged in m ultilevel radiculopathy (n ot sen sitive). Most h elpfu l in evaluatin g proxim al root slow in g, e.g. GBS (p. 184). H-reflex: pract ical ≈ on ly in S1 n er ve root, sim ilar in form ation to th e an kle jerk. St im ulation of Ia a erent fibers passes through a m onosynaptic connection causing an orth odrom ic alpha-m otor action potential that can be m easured in the triceps surae. Volition al act ivity: th e m otor un it action poten tial (MUAP) can be assessed on ly w ith volun tar y m uscle con tract ion by th e patien t. Com pon en ts of th e MUAP m easured in clude: am plitu de, rise t im e, duration , an d n um ber of ph ases (crossin gs of th e baselin e). Polyph asic poten tials: MUAPs w ith > 4 ph ases. Norm ally com prise < 15% of MUAPs. Follow in g a n er ve injur y, abn orm ally in creased polyphasic poten tials can be seen 6–8 w eeks after rein n er vation begin s, gradually in crease over several m on th s, an d th en begin to w an e (as firin g becom es m ore syn ch r on ou s). Myoton ia: th ere are a n um ber of m yoton ic con dition s, in cluding m yoton ic dyst rophy in w h ich th ere is sustain ed con tract ion of th e m uscle. Classic EMG fin din g: “dive bom ber” soun d due to m yo- tonic discharges. EMG for radiculopat hy EMG pearls for the neurosurgeon Gen eral prin ciples: ● EMG – if a reliable m otor exam can be don e, th e EMG w ill n ot likely add any in form ation . A n orm al m otor exam w ill usually be associated w ith a n orm al EMG ● EMG is n ot extrem ely sen sitive for radiculopathy (e.g. irritative radiculopathy m igh t n ot be picked up), th is is m ore likely in th e cer vical region th an lum bar. How ever, w h en abn orm al, EMG is ver y sp e cific ● EMG is best reser ved for cases w ith docum en ted w eakn ess w h ere addition al localizing/progn ostic in form ation is n eeded, or w h en th e pat ien t’s st ren gth can n ot be reliably assessed (in abilit y to cooperate, fun ct ion al overlay…) ● Tim in g ○ It takes about 3 w eeks after on set of radiculopathy for th e EMG to reliably sh ow any fin din gs ○ “Acute ch anges” begin at about 3 w eeks an d can last up to about 6 m on th s ○ Ch ron ic ch anges can be seen startin g at about 6 m on th s, an d m ay persist in defin itely

244 Im aging and Diagnostics Cer vical EMG: ● EMG is m ost h elpfu l for n er ve roots C5-T1. Th ere are n o good m uscles to reliably test C3-4, an d com pression here m ay cause findings in lower nerve roots Lum bar EMG: ● If lum bar MRI is n orm al in a pat ien t w ith eviden ce of m otor w eakn ess (e.g. foot drop), do an EMG to look for periph eral n europathy (again , a good m otor exam can give th e sam e in fo). If th e EMG is n egative for periph eral n europathy (e.g. peron eal n er ve palsy) th en do an MRI (or CT) of abdom en an d pelvis to look for pelvic floor t um or Fin d in g s In clude spon tan eous act ivity (fibs & PSW s, see above). Th e earliest possible fin din g (w ith in 2–3 d) is reduced recruitm en t w ith volition al act ivity, but th is occurs on ly w ith sign ifican t com pression of m otor fibers. EMG is useful if th ere is a con cern about possible overlappin g periph eral n europathy (e.g. carpal t un n el syn drom e vs. C6 radiculopathy). EMG criteria for radiculopathy 1. fibrillations and/or positive sharp w aves in at least 2 m uscles innervated by a single ner ve root in question, but by 2 di erent peripheral nerves 2. abn orm al paraspin als: th is supports th e diagn osis, but is n ot required sin ce paraspin als w ill be norm al in ≈ 50% Lum bar radiculopathy from h ern iated disc W ith radiculopathy, SNAP is usually n orm al (see above). Paraspin al m uscle fibrillation s m ay occur. Accuracy in predicting level of involvem en t10 is ≈ 84%. Foot drop: th e sh ort h ead of th e biceps fem oris in th e LE is th e first m uscle in n er vated by th e peron eal division of th e sciatic n er ve at or just above th e popliteal fossa just after th e n er ve splits o from th e sciatic n er ve. In cases e.g. of foot drop it is a good m uscle to test to determ in e if th ere is a peron eal n europathy vs. a m ore proxim al lesion (i.e. above th e popliteal fossa). Fin din gs w ith h ealin g radiculopathy (e.g. follow in g discectomy or spon tan eous h ealing): ● m otor poten tials return first (if n er ve injur y w ere “com plete”, it w ould take a m on th to return ) ● if lost, sen sory potentials return last or m ay not return ● follow in g lam in ectom y, paraspin al poten tials m ay n o lon ger be useful for EMG because cutt in g th e m uscles during surger y alters th eir elect rical sign als result in g in e ect ive den er vation due to m uscle injur y. Fibs an d PSW s decrease in am plit ude over t im e but m ay rem ain present 14 indefinitely EMG in plexopathy Reduct ion of SNAP w ith no pa ra spina l m uscle fibrillation s (th e dorsal ram i exit proxim ally to in n er- vate th e paraspin als, an d are involved ≈ only w ith root lesion s). EMG in nerve root avulsion Produces m uscles w eakn ess an d sen sor y loss w ith n orm al SNAP sin ce th e lesion is proxim al to th e dorsal root gan glion (w h ere th e cell bodies for th e sen sor y n er ves are located). Re fe r e n ce s [4] Ch iap pa KH. Evoked Poten t ials in Clin ical Med icin e (Secon d of Tw o Parts). N En gl J Med . 1982; [1] Don n egan JH, Blit t CD. In : Th e Elect roen cep h alo- 306:1205–1211 gram . Mon itoring in Anesth esia an d Crit ical Care Med icin e. New York: Ch urch ill Livin gston e; [5] Gregori EM, Goldrin g S. Localization of Fu n ct ion in 1985:323–343 th e Excision of Lesion s from th e Sen sorim otor Re- gion. J Neurosurg. 1984; 61:1047–1054 [2] Holly LT, Matz PG, An d erson PA, Gro MW , Hear y RF, Kaiser MG, Mum m anen i PV, Ryken TC, Ch oudh ri [6] Woolsey CN, Erickson TC, Gibson W E. Localization TF, Vresilovic EJ, Resn ick DK. Clin ical progn ostic in Som atic Sen sor y an d Motor Areas of Hum an Cer- in dicators of surgical outcom e in cer vical spon dy- ebral Cortex as Determ in ed by Direct Recording of lotic m yelopathy. J Neurosurg: Spine. 2009; Evoked Poten t ials an d Elect rical Stim ulat ion . J Neu - 11:112–118 rosurg. 1979; 51:476–506 [3] Ch iap p a KH. Evoked Poten t ials in Clin ical Medicin e [7] Roh M, W ilson -Hold en T, Padberg A. Th e u tilit y of (First of Tw o Parts). N Engl J Med. 1982; 306:1140– SSEP m on itorin g durin g cervical spin e surgery: 1150 How often does it prom pt in tervention an d a ect outcom e. 2002

Electrodiagnostics 245 [8] Vitale MG, Skaggs DL, Pace GI, Wrigh t ML, Matsu - [9] Benecke R, Conrad B. Th e distal sen sor y n er ve m oto H, An derson RCE, Brockm eyer DL, Dorm an s JP, act ion p oten t ial as a diagn ostic tool for th e di eren - Em an s JB, Erickson MA, Flyn n JM, Glotzbecker MP, t iation of lesion s in dorsal roots an d perip h eral Ibrah im KN, Lew is SJ, Luh m an n SJ, Men diratta A, Rich ards BS, III, San ders JO, Sh ah SA, Sm ith JT, Song n er ves. J Neurol. 1980; 223:231–239 KM, Spon seller PD, Sucato DJ, Roye DP, Len ke LG. [10] Youn g A, Gett y J, Jackson A, et al. Variat ions in th e Best Pract ices in In traoperative Neu rom on itorin g in Pattern of Mu scle In n ervation by th e L5 an d S1 Spine Deform it y Surgery: Developm en t of an In t ra- Nerve Roots. Sp in e. 1983; 8:616–624 operative Ch ecklist to Op tim ize Respon se. Sp in e Deform it y. 2014; 2:333–339 14



Part IV 15 Prim ary 248 In t ra cra n ia l 265 Developm ent al Anom alies Anom alies 277 16 Prim ary Spinal Anom alies 17 Prim ary Cr a n io sp in a l Anom alies IV

248 Developm ental Anom alies 15 Prim ary Int racranial Anom alies 15.1 Arachnoid cyst s, int racranial 15.1.1 General inform at ion Key concept s ● a congenital abnormality, m ost common in middle fossa, cerebellopontine angle (CPA), suprasellar region, and posterior fossa ● most are asym ptomatic (i.e. an incidental finding) except in the suprasellar region ● im aging often shows rem odeling of bone; imaging characteristics exactly mimic CSF on CT or MRI in m ost cases ● recomm endation for incidentally discovered arachnoid cyst in adults: a single follow-up imaging study in 6–8 months is usually adequate to rule-out any increase in size. Subsequent studies only if concerning symptoms develop AKA leptom en in geal cysts, dist in ct from postt raum atic leptom en in geal cysts (AKA grow in g skull fract ures) (p. 915), an d un related to in fect ion . Arach n oid cysts (AC) are congen ital lesion s th at arise during developm en t from splitt in g of arach noid m em bran e (th us th ey are tech n ically in t ra-arach- n oid cysts) an d con tain fluid th at is usually iden tical to CSF. Th ey do n ot com m un icate w ith th e ven - t ricles or subarach n oid space. May be un loculated or m ay h ave septat ion s. Typically lin ed w ith m en in goth elial cells positive for epith elial m em bran e an tigen (EMA) an d n egative for carcin oem - br yonic an tigen (CEA). AC m ay also occur in th e spin al can al. “Tem poral lobe agen esis syn drom e” is a label th at h ad been used to describe th e fin din gs w ith m iddle cran ial fossa ACs. Th is term is n ow obsolete sin ce brain volum es on each side are act ually th e sam e,1 bon e expan sion an d sh ift of brain m atter accoun t for th e paren chym a th at appears to be replaced by th e AC. Tw o t ypes of h istological fin din gs2: 1. “sim ple arach n oid cysts”: arachn oid lin in g w ith cells th at appear to be capable of active CSF secretion . Middle fossa cysts seem to be exclusively of th is t ype 2. cysts w ith m ore com plex lin in g w h ich m ay also con tain n euroglia, epen dym a, an d oth er tissue types 15.1.2 Epidem iology of int racranial arachnoid cyst s 1 5 In ciden ce: 5 per 1000 in autopsy series. Com prise ≈ 1%of in tracran ial m asses. Male:fem ale ratio is 4:1. More com m on on th e left side. Bilateral arach n oid cysts m ay occur in Hurler syn drom e (a m ucopolysacch aridosis). 15.1.3 Dist ribut ion Alm ost all occur in relation to an arach n oid cistern (exception : in trasellar, th e on ly on e th at is extra- dural, Table 15.1). Epiderm oid cysts in th e cerebellopon tin e an gle (CPA) m ay m im ic an arach n oid cyst, but are h igh sign al on DWI MRI. See also di eren tial diagn osis of m idlin e posterior fossa arach noid cysts (p.256). 15.1.4 Present at ion Most ACs are asym ptom at ic. Th ose th at becom e sym ptom atic usually do so in early ch ildh ood.4 Th e presen tation varies w ith location of th e cyst, an d often tim es appear m ild con siderin g th e large size of some. Typical presen tation s are sh ow n in Table 15.2 4 an d in clude: 1. sym ptom s of in t racran ial hyper ten sion (elevated ICP): H/A, N/V, leth argy 2. seizures 3. sudden deterioration: