Duane E. Haines - Neuroanatomy An Atlas of Structures, Sections, and Systems

A The Cranial Nerves 43 Abducens nerve Facial nerve Vestibulocochlear Olivary eminence nerve Glossopharyngeal Postolivary sulcus nerve Preolivary sulcus Vagus nerve B Hypoglossal nerve Preolivary sulcus Pyramid Retroolivary sulcus Olive (inferior)(postolivary sulcus) Glossopharyngeal Glossopharyngeal nerve Restiform body nerve Tonsil of cerebellum Flocculus Fourth ventricle Pyramid Olive (inferior) Cerebellum Vagus nerve C Fourth ventricle Retroolivary sulcus Pyramid Olivary eminenceTonsil of cerebellum Postolivary sulcus Vagus nerve Cerebellum Tonsil of cerebellum D Vagus nerve Restiform body Fourth ventricle2-44 The glossopharyngeal (IX) and vagus (X) nerves (A) exit the cle is smaller. The ninth and tenth cranial nerves and the spinal portionlateral aspect of the medulla via the postolivary sulcus; the ninth nerve of the accessory nerve (XI) exit the skull via the jugular foramen.exits rostral to the row of rootlets comprising the tenth nerve (A).These nerves are generally in line with the exits of the facial and Glossopharyngeal neuralgia is a lancinating pain originating fromtrigeminal nerves; all of these are mixed nerves. The exit of the glos- the territories served by the ninth and tenth nerves at the base of thesopharyngeal nerve (A, B) is close to the pons–medulla junction and tongue and throat. Trigger events may include chewing and swallow-correlates with the corresponding shape (more rectangular) of the ing. Lesions of nerves passing through the jugular foramen (IX, X, XI)medulla. The vagus nerve exits at a slightly more caudal position (A, may result in loss of the gag reflex (motor limb via ninth nerve), andC, D); the shape of the medulla is more square and the fourth ventri- drooping of the ipsilateral shoulder accompanied by an inability to turn the head to the opposite side against resistance (eleventh nerve).

44 External Morphology of the Central Nervous System Facial nerve Vestibulocochlear A nerve Glossopharyngeal Abducens nerve nerve Olivary eminence Vagus nerve Postolivary sulcus Preolivary sulcus Hypoglossal nerve B Pyramid Preolivary sulcus Olivary eminence Hypoglossal nerve Restiform body Postolivary sulcus Tonsil of cerebellum Vagus nerve C Hypoglossal nerve MedullaTonsil of cerebellum Cerebellum2-45 The hypoglossal nerve (XII) (A) exits the inferolateral aspect teristic position of the hypoglossal nerve in the subarachnoid space andof the medulla via the preolivary sulcus. This cranial nerve exits in line its relation to the overall shape of the medulla. This shape is indicativewith the abducens nerve found at the pons–medulla junction and in line of a cranial nerve exiting at more mid-to-caudal medullary levels. In B,with the exits of the third and fourth nerves of the midbrain. The note its relationship to the preolivary sulcus and olivary eminence. Thetwelfth nerve exit is characteristically located laterally adjacent to the hypoglossal exits the base of the skull by traversing the hypoglossalpyramid, which contains corticospinal fibers. canal. A lesion of the hypoglossal nerve results in a deviation of the tongue to the ipsilateral side on attempted protrusion. In axial MRI (B, T2-weighted; C, T1-weighted), note the charac-

Precentral gyrus (PrCGy) The Insula 45 Superior frontal Central sulcus (CSul) gyrus Postcentral gyrus (PoCGy) Middle frontal gyrus (MFGy) Gyri longi (GyLon–long gyri of the insula) Gyri breves(GyBr–short gyri Transverse temporal gyrus (TrTemGy) of the insula) Temporal lobe (TLob) Central sulcus of the insula (CSulIn) Limen insulae (LimIn)PrCGy PoCGyMFGy CSul GyBr TrTemGy LimIn GyLon TLob CSulInPrCGy CSulMFGy PoCGyGyBr CSulInTLob GyLon 2-46 Lateral view of the left cerebral hemisphere with the cortex overlying the insula removed. Structures characteristic of the insular cortex, and immediately adjacent areas, are clearly seen in the two MRIs in the sagittal plane through lateral portions of the hemisphere (inversion recovery—upper; T1-weighted image—lower).

46 External Morphology of the Central Nervous System Comparison of Cerebral versus Spinal MeningesCEREBRAL SPINALDura Dura• adherent to inner table of skull (no epidural space) • separated from vertebrae by epidural space• composed of two fused layers (periosteal and meningeal), • composed of one layer (spinal dura only; vertebrae which split to form sinuses have their own periosteum)Arachnoid (outer part of leptomeninges) Arachnoid (outer part of leptomeninges)• attached to dura in living condition (no subdural space) • attached to dura in living condition (no subdural space)• arachnoid villi (in superior sagittal sinus)• arachnoid trabeculae • no arachnoid villi• subarachnoid space with many cisterns • few or no arachnoid trabeculae but larger arachnoid septae • subarachnoid space with one cisternPia (inner part of leptomeninges) Pia (inner part of leptomeninges)• intimately adherent to surface of brain • intimately adherent to surface of cord• no pial specializations • specializations in the form of denticulate ligaments,• follows vessels as they pierce the cerebral cortex filum terminale, and linea splendens • follows vessels as they pierce the cordMeningitis, Meningeal, Hemorrhages, Meningioma A wide variety of disease processes and lesions may involve the commonly seen in younger patients, are usually detected immediatelymeninges; only a few examples are mentioned here. or within a few hours after the precipitating incident. Chronic subdural hematomas, usually seen in the elderly, are frequently of unknown ori- Bacterial infections of the meninges (bacterial meningitis) are gin; may take days or weeks to become symptomatic; and cause a pro-commonly called leptomeningitis because the causative organisms are gressive change in mental status of the patient. This lesion appearsusually found in the subarachnoid space and involve the pia and arach- “long and thin,” compared to an epidural hematoma, follows the sur-noid. The organism seen in about one-half of adult cases is Streptococcus face of the brain, and may extend for considerable distances (see Fig.pneumoniae, while in neonates and children up to about 1 year it is Es- 2-48 on p. 48 and Fig. 2-51 on p. 51). Treatment is surgical evacua-cherichia coli. The patient becomes acutely ill (i.e., confusion, fever, stiff tion (for larger or acute lesions) or close monitoring for small, asymp-neck, stupor), may have generalized or focal signs/symptoms, and, if tomatic, or chronic lesions.not treated rapidly, will likely die. Treatment is with appropriate an-tibiotics. Patients with viral meningitis may become ill over a period The most common cause of subarachnoid hemorrhage is trauma.of several days, experience headache, confusion, and fever, but, with In approximately 80% of patients with spontaneous (nontrau-supportive care, will recover after an acute phase of approximately 1–2 matic) subarachnoid hemorrhage, the precipitating event is ruptureweeks. These patients usually recover with no permanent deficits. of an intracranial aneurysm. Symptomatic bleeding from an arteriove- nous malformation occurs in approximately 5% of cases. Blood collects The most common cause of an epidural (extradural) hematoma in, and percolates through, the subarachnoid space and cisterns (seeis a skull fracture that results in a laceration of a major dural vessel, such Fig. 2-51 on page 51). Sometimes, the deficits seen (assuming the pa-as the middle meningeal artery. In approximately 15% of cases, bleed- tient is not in coma) may be a clue as to location, especially if cranialing may come from a venous sinus. The extravasated blood dissects the nerves are nearby. Onset is sudden; the patient complains of an excru-dura mater off the inner table of the skull; there is no preexisting (ex- ciating headache and may remain conscious, become lethargic and dis-tradural) space for the blood to enter. These lesions are frequently oriented, or may be comatose. Treatment of an aneurysm is to surgi-large, lens (lenticular) shaped, may appear loculated, and are “short cally occlude it (by clip or coil), if possible, and to protect against theand thick” compared to subdural hematomas (see Fig. 2-48 on page development of vasospasm. During surgery, some blood in the sub-48). The patient may lapse into a coma and, if the lesion is left un- arachnoid space and cisterns may be removed.treated, death may result. In some cases, the patient may initially beunconscious followed by a lucid interval (the patient is wide awake), Tumors of the meninges (meningiomas) are classified in differentthen subsequently deteriorate rapidly and die; this is called “talk and ways but they usually arise from arachnoid cap/stem cells (a smalldie.” Treatment of choice for large lesions is surgical removal of the number are dural in origin) around the villi or at places where vesselsclot and coagulation of the damaged vessel. or cranial nerves penetrate the dura-arachnoid. These tumors grow slowly (symptoms may develop almost imperceptibly over years), are Tearing of bridging veins (veins passing from the brain outward histologically benign, may result in hyperostosis of the overlying skull,through the arachnoid and dura), usually the result of trauma, is a com- and frequently contain calcifications. In decreasing order, menin-mon cause of subdural hematoma. This designation is somewhat a giomas are found in the following locations: parasagittal area ϩ falxmisnomer because the extravasated blood actually dissects through a (together 29%), convexity 15%, sella 13%, sphenoid ridge 12%, andspecialized, yet structurally weak, cell layer at the dura-arachnoid in- olfactory groove 10%. Treatment is primarily by surgical removal, al-terface; this is the dural border cell layer. There is no preexisting “sub- though some meningiomas are treated by radiotherapy.dural space” in the normal brain. Acute subdural hematomas, more

The Meninges, Cisterns, and Meningeal and Cisternal Hemorrhages 47 Skull Superior sagittal sinus Arachnoid villusCerebrum Lateral lacunae Dura materCerebellum Transverse Arachnoid mater sinus Arachnoid trabeculae Tentorium Pia mater cerebelli Falx cerebri Cistern Skull Dura mater Subarachnoid space Arachnoid mater Cerebral vessel and branch Pia mater Arachnoid trabeculae Vertebrae Spinal nerves Spinal vessel Dura mater Dura mater Intervertebral Conus medullaris ligament Cauda equina Epidural spaceLumbar cistern Filum terminale (interum) Vertebra Arachnoid mater Coccygeal ligament (filum terminale externum) Denticulate ligament Pia materCoccyx2-47 Semidiagrammatic representation of the central nervous sys- fourth ventricles. It circulates through the ventricular system (small ar-tem and its associated meninges. The details show the relationships of rows) and enters the subarachnoid space via the medial foramen of Ma-the meninges in the area of the superior sagittal sinus, on the lateral as- gendie and the two lateral foramen of Luschka. In the living situationpect of the cerebral hemisphere, and around the spinal cord. Cere- the arachnoid is attached to the inner surface of the dura. There is nobrospinal fluid is produced by the choroid plexi of lateral, third, and actual or potential subdural space.

48 External Morphology of the Central Nervous System ABCD Hemorrhage in brain2-48 Examples of epidural (extradural) hemorrhages (A, B) and of where the blood is replaced by fluid, and the subacute phase by theacute (C) and subacute (D) subdural hematoma. Note the lenticular middle arrow where fresher blood has entered the lesion. Note the ex-shape of the epidural lesions (A, B), their loculated appearance, and tent of this lesion on the surface of the cortex and its narrowness com-their location external to the substance of the brain. In contrast, the pared to epidural lesions. The patient in D also has small hemorrhagesacute subdural lesion (C) is quite thin and extends over a longer dis- into the substance of the brain, the larger of these in the region of thetance on the cortex. genu of the internal capsule. Images A–D are CT. For additional com- ments on epidural and subdural hemorrhages see page 46. In D, the subdural hematoma has both chronic and subacute phases.The chronic phase is indicated by the upper two and lower two arrows

The Meninges, Cisterns, and Meningeal and Cisternal Hemorrhages 49AB C Blood in third ventricleBlood in frontal lobe Temporal horn Blood in cerebral aqueduct2-49 Examples of hemorrhages into the substance of the brain that, Blood in the substance of the brain and in the ventricular system mayin some cases, have also resulted in blood in the ventricular system. also result from trauma (C). In this example (C), blood is seen in theThe large hemorrhages into the hemisphere (A, B) have resulted in en- frontal lobe and in the third ventricle and cerebral aqueduct. The en-largement of the ventricles, a midline shift, and, in the case of A, a larged temporal horns (C) of the lateral ventricles are consistent withsmall amount of blood in the posterior horn of the lateral ventricle. In the interruption of CSF flow through the cerebral aqueduct (noncom-these examples, the lesion is most likely a result of hemorrhage from municating hydrocephalus). Images A–C are CT.lenticulostriate branches of the M1 segment.

50 External Morphology of the Central Nervous System Paracallosal cistern Quadrigeminal cistern A B Lamina terminalis cistern Fourth ventricle Chiasmatic cistern C Interpeduncular cistern D Prepontine cistern Premedullary cistern Cisterna magna B Lamina terminalis cistern Optic tract Sylvian cistern Interpeduncular cistern Crural cistern Ambient cistern Midbrain Inferior colliculus Quadrigeminal cistern Prepontine cistern Basilar artery C Basilar pons Fourth ventricle Trigeminal nerve Premedullary cistern Superior cerebellopontine Inferior cerebellopontine cistern cistern D Medulla Cisterna magna2-50 A median sagittal MRI (A, T2-weighted) of the brain show- contain arteries and veins, roots of cranial nerves, and, of course, cere- brospinal fluid. Consequently, the subarachnoid space and cisterns areing the positions of the major cisterns associated with midline struc- continuous one with the other. In addition, the subarachnoid spacetures. Axial views of the midbrain (B, T1-weighted), pons (C, around the brain is continuous with that around the spinal cord. Com-T2-weighted), and medulla (D, T2-weighted) represent the corre- pare these cisterns with blood-filled parts of the subarachnoid space andsponding planes indicated in the sagittal view (A). cisterns in Figure 2-51 on the facing page. Cisterns are the enlarged portions of the subarachnoid space that

The Meninges, Cisterns, and Meningeal and Cisternal Hemorrhages 51 A BLamina terminalis Subdural cistern hemorrhageSupraoptic recess Sylvian Interpeduncular cistern cistern Crural cistern Temporal horn Blood on insular cortex Midbrain Quadrigeminal Ambient cistern cistern C DLamina terminalis Third cistern ventricle Sylvian Blood on cistern insula Crural Interpeduncular cistern cistern Cerebellum Ambient cisternBlood on tentorium cerebelli Rostral part of fourth ventricle2-51 Blood in the subarachnoid space and cisterns. In these CT ex- blood on the cortex of the insula. In C, the blood is located around theamples, blood occupies the subarachnoid space and cisterns, outlining midbrain (crural and ambient cisterns), extends into the Sylvian cis-these areas in white. Consequently, the shape of the cisterns is indi- tern, and into the cistern of the lamina terminalis. The sharp interfacecated by the configuration of the white area, the white area represent- between the lamina terminalis cistern (containing blood) and the thirding blood. ventricle (devoid of blood) represents the position of the lamina ter- minalis. In D, blood is located in cisterns around the pons but avoids Around the base of the brain (A), it is easy to identify the cisterns the rostral part of the fourth ventricle. Compare these images with therelated to the midbrain, the supraoptic recess which is devoid of blood, locations of some of the comparable cisterns as seen in Figure 2-50 onand blood extending laterally into the Sylvian cistern. In some cases the facing page. Images A–D are CT.(B), subdural hemorrhage may penetrate the arachnoid membrane andresult in blood infiltrating between gyri, such as this example with

52 External Morphology of the Central Nervous System Massa intermedia Body of lateral Pineal recess Third ventricle ventricle Suprapineal recessAnterior horn of lateral ventricle Posterior commissure PinealInterventricular Atrium of lateral ventricle foramen (and glomus choroideum)Anterior commissure Posterior horn of lateral ventricle Lamina terminalis Tectum Infundibular recess Cerebral aqueduct Supraoptic recess Fourth ventricle Optic chiasm Lateral recess of fourth ventricle Infundibulum Mammillary body Foramen of Amygdaloid nuclear complex Luschka Inferior horn of lateral ventricle Dorsal cerebellomedullary cistern (cisterna magna) Bordering Structures Ventricular Space Genu of corpus callosum Anterior horn of lateral ventricleHead of caudate nucleus Septum pellucidum Body of lateral ventricle (ventral to body of corpus callosum) Body of caudate nucleus Third ventricle Fornix Suprapineal recessAmygdaloid nuclear complex Inferior horn of Tail of caudate nucleus lateral ventricleHippocampal formation Cerebral aqueduct Splenium of corpus callosumOptic radiations Atrium of lateral ventricle Tapetum (contains glomus choroideum) Lateral recess of fourth ventricle Fourth ventricle Posterior horn of lateral ventricle2-52 Lateral (above) and dorsal (below) views of the ventricles and colors are continued in Figure 2-53 on the facing page. Note the rela-the choroid plexus. The dashed lines show the approximate positions tionships between the choroid plexus and various parts of the ventric-of some of the important structures that border on the ventricular ular system. The large expanded portion of the choroid plexus foundspace. The choroid plexus is shown in red and structures bordering on in the area of the atrium is the glomus (glomus choroideum). See Fig-the various portions of the ventricular spaces are color-coded; these ure 8-12 on p. 251 for details of blood supply to the choroid plexus.

The Ventricles and Ventricular Hemorrhage 53A Corpus callosum Caudate nucleus (body) B Corpus callosum (body) Caudate nucleus (body) Anterior horn of Stria terminalis Corpus callosum (body) lateral ventricle Septum Body of lateral ventricle Septum pellucidum C Choroid plexus (CP) pellucidum Fornix (F) Fornix CP Caudate nucleus Body of lateral Third ventricle (head) ventricle Dorsal thalamus Corpus callosum F Interventricular Massa intermedia (rostrum) foramen Mammillary body Anterior Hypothalamus commissure Caudate nucleus Gyrus rectus Third ventricle Fornix Hypothalamus Dorsal thalamus Third ventricle Optic chiasm Amygdaloid nuclear complex A BC D E D Optic tract F Inferior horn of G lateral ventricle Body of lateral E ventricle Optic radiations Optic radiations Corpus callosum G Tapetum F Tapetum Pulvinar Pineal Cerebral aqueduct Inferior horn of lateral ventricle Corpus callosum Hippocampal formation (splenium) Caudate nucleus (tail) Calcarine Atrium of lateral sulcus ventricle Calcar avis Hippocampal formation Posterior horn of lateral ventricle2-53 Lateral view of the ventricular system and corresponding and the majority of structures labeled have some direct relevance to thesemidiagrammatic cross-sectional representations from rostral (A) to ventricular space at that particular level. The color-coding correspondscaudal (G) identifying specific structures that border on the ventricu- to that shown in Figure 2-52 on the facing page.lar space. In the cross-sections, the ventricle is outlined by a heavy line,

54 External Morphology of the Central Nervous System B A Anterior horn of Anterior horn lateral ventricle Third Atrium of ventricle lateral ventriclePosterior horn of lateral ventricle C Basilar pons Fourth ventricle Temporal horn of lateral ventricleTegmentum of pons Cerebellum DFourth ventricle Pons-medulla junction Cerebellum Lateral recess of fourth ventricle2-54 Examples of hemorrhage occupying portions of the ventric- third ventricle (B). Blood also clearly outlines central portions of theular system (ventricular hemorrhage). In these CT images, blood ap- fourth ventricle (C) and caudal portions of the fourth ventricle (D), in-pears white within the ventricles. Consequently, the shape of the ven- cluding an extension of blood into the left lateral recess of the fourthtricular system is outlined by the white area, and the specific portion ventricle. In addition to these images, Figure 2-49 on page 49 showsof the ventricular system is correspondingly labeled. blood in the cerebral aqueduct and in the most inferior portions of the third ventricle. Images A–D are CT. Note blood in the anterior horn, atrium, and posterior horn of thelateral ventricles (A, B), and blood clearly outlining the shape of the

CHAPTER 3 Dissections of theCentral Nervous System

56 Dissections of the Central Nervous System Central sulcus Gyri: Superior parietal lobule Precentral Supramarginal gyrus Postcentral Long insular gyriShort insular gyri Central sulcus of insula Gyri: Transverse temporal Superior temporal Superior temporal sulcus3-1 Lateral view of the right cerebral hemisphere with the inferior removed to show the insular cortex, transverse temporal gyri, and re-and parts of the middle frontal gyri and precentral and postcentral gyri lated structures.Superior longitudinal fasciculus Uncinate fasciculus External capsule3-2 Dissection of the lateral aspect of the right cerebral hemisphere subcortical white matter. This dissection is deep to that shown in Fig-showing the locations and relationships of some of the main bundles of ure 3-1 (above) and superficial to that shown in Figure 3-3 on page 57.

Corona radiata Lateral, Medial, and Ventral Aspects 57Lenticular Superior nucleus longitudinal fasciculus Uncinate fasciculus Occiptofrontal fasciculus3-3 Dissection of the lateral aspect of the right cerebral hemisphere lus. The lenticular nucleus is shown in situ, lateral to the internal cap-showing the relationship between fibers radiating from the internal sule. This is a deeper dissection of the specimen shown in Figure 3-2capsule (corona radiata) and those of the superior longitudinal fascicu- on page 56.Internal capsule (IC): Posterior limb Genu Anterior limb Optic radiations Retrolenticular limb of IC3-4 Dissection of the lateral aspect of the right cerebral hemisphere This is a deeper dissection of the specimen shown in Figure 3-3showing the internal capsule and the concavity left by removal of the (above).lenticular nucleus. Note the other bundles of subcortical white matter.

58 Dissections of the Central Nervous System Cingulum Calcarine sulcusCorpus callosum Spiral fibers of hippocampus 3-5 Dissection of the medial aspect of the left cerebral hemisphere showing the cingulum and spiral fibers of the hippocampus. Optic: Infundibulum Nerve Amygdaloid complex Chiasm Tract Inferior horn of lateral ventricle Crus cerebri HippocampusLateral geniculate Calcar avis body Posterior horn of lateral ventricle Medial geniculate body 3-6 Overview of a dissection showing the ventral aspect of the cerebral hemispheres. Note the structures related to ventricular spaces and the structures located at the mesencephalon–diencephalon inter- face. A number of structures in addition to those labeled can be iden- tified.

Overall Views 59 Optic chiasm Infundibulum Optic nerve Olfactory tract Tuber cinereum Anterior perforated substance Mammillary body Crus cerebri Amygdaloid complex Optic tract Temporal horn Posterior perforated Hippocampus substance Substantia nigraMedial geniculate body Red nucleusLateral geniculate body Periaqueductal gray Brachium of Choroid plexus superior colliculus Superior colliculus Great cerebral vein Pulvinar Splenium of corpus callosum3-7 Detailed view of a dissection showing the ventral aspects of the crus cerebri; and the relationship of hypothalamic structures on thecerebral hemispheres; this is of the same specimen shown in Figure ventral aspect of the brain. In addition to those labeled, other struc-3-6 on page 58. Note the continuum of optic nerve, chiasm, and tract tures can be identified.to the lateral geniculate body; the relationship of the optic tract to the

60 Dissections of the Central Nervous System Corpus callosum Head of caudateSeptum pellucidum Transverse Dorsal thalamus temporal gyrus Fornix Choroid plexus3-8 Dissected view of the brain from the dorsal aspect showing of insular and transverse temporal gyri, the fornix, and other structuresstructures associated with the lateral ventricles. Note the appearance in addition to those labeled. Anterior horn of Column of fornix lateral ventricle Head of caudateInterventricular Anterior nucleus foramen of thalamus Third ventricle Massa intermedia Habenula Pineal Colliculi3-9 Dissected view of the brain from the dorsal aspect showing lat- tufts of choroid plexus identify the locations of the interventriculareral and third ventricles, the dorsal surface of the diencephalon, the in- foramina. Note the massa intermedia traversing the third ventricle andsula and transverse temporal gyri, and the colliculi. The majority of the other structures in addition to those labeled.fornix and the roof of the third ventricle have been removed. The small

Transverse Fornix Overall Views 61 cerebral fissure Brachium of superior colliculus Suprapineal recess Brachium of inferior colliculus Pineal Optic radiationsCaudate nucleus Choroid CC SC CC Tapetum plexus Glomus IC Temporal Pulvinar inferior horn ** Hippocampus Brachium of SC Frenulum Lateralgeniculate body Medial geniculate bodyAnterior medullary Cerebellar peduncles: velum Middle Superior Flocculus Inferior Lateral recess, Posterior column: fourth ventricle Tubercles Fasciculi3-10 A dissection showing caudal diencephalic structures, several culi (SC), the inferior colliculi (IC), and the crus cerebri (CC), as seentelencephalic structures, and the interface of the mesencephalon with from the dorsal aspect, are identified. The asterisks represent the exitcaudal parts of the thalamus. On the right side, note the continuation points of the trochlear nerves. For further details of the dorsal brain-between the fornix and hippocampus; on the left, these structures have stem, see Figure 2-34 on page 34. Note structures in addition to thosebeen removed to expose the underlying pulvinar. The superior colli- labeled.

CHAPTER 4Internal Morphology of the Brain in Slices and MRIBrain Slices in the Coronal Plane with MRIOrientation to Coronal MRIs: When looking at a coronal To reinforce this concept, the rostral surface of each coronalMRI image, you are viewing the image as if you are looking at brain slice was photographed. So, when looking at the slice, thethe face of the patient. Consequently, the observer’s right is the observer’s right field of view is the left side of the brain slice. Thisleft side of the brain in the MRI and the left side of the patient’s view of the slice correlates exactly with the orientation of thebrain. Obviously, the concept of what is the left side versus what brain as seen in the accompanying coronal MRIs.is the right side of the patient’s brain is enormously importantwhen using MRI (or CT) to diagnose a neurologically impairedindividual.

64 Internal Morphology of the Brain in Slices and MRI Cingulate gyrus (CinGy) Cingulum (Cin) Body of corpus callosum (BCorCl) Head of caudate nucleus (HCaNu) Anterior horn of lateral ventricle (AH of Lven) Anterior limb of Septum pellucidum internal capsule (ALIntCap) Rostrum of corpus callosum (RCorCl) Putamen (Put) External capsule Subcallosal gyrus (ExtCap) Insula (In) Claustrum (Cl) Middle cerebral Extreme capsule artery (ExtrmCap) Nucleus accumbens Temporal lobe (NuAcc) (TemLb) Optic nerve (OpNr) BCorCl HCaNu CinGy AH of Cin LVen ALIntCap BCorCl Put AH of In LVenExtrmCap ExtCap RCorCl Cl NuAcc TemLb ExtrmCap OpNr Olfactory tract4-1 The rostral surface of a coronal section of brain through the an- MRI images (both are inversion recovery) are at the same plane andterior limb of the internal capsule and the head of the caudate nucleus. The two show many of the structures identified in the brain slice.

Coronal Brain Slice—MRI Correlation 65 Body of corpus Head of caudate nucleus callosum (BCorCl) (HCaNu) Septum (Sep) Anterior limb of internal capsule (ALintCap)Corona radiata (CorRad) Column of fornix Putamen (Put) (ColFor) External Capsule (ExtCap) Insula (In) Anterior Claustrum (Cl) commissure (AC) Extreme capsule (ExtCap) Claustrum Ventral striatum Globus pallidus (GP) Ventral pallidum Middle cerebral Supraoptic recess artery Optic chiasm (OpCh) Infundibulum (Inf) Uncus Sep BCorCl Sep CorRadCorRad HCaNu GPColFor ALIntCap AC In OpCh Put GP Cl AC AC Optic Third tract ventricle Inf ExtrmCap4-2 The rostral surface of a coronal section of brain through the level ages (both are inversion recovery) are at the same plane and show manyof the anterior commissure and the column of the fornix. The two MRI im- of the structures identified in the brain slice.

66 Internal Morphology of the Brain in Slices and MRI Body of lateral Body of corpus callosum (BCorCl) ventricle (BLatVen) Anterior tubercle of thalamus (AntTub)Corona radiata (CorRad) Head of caudate nucleus Stria terminalis and (HCaNu) terminal vein Insula (In) Internal capsule (IntCap) External capsule Putamen (Put) (ExtCap) Globus pallidus (GP) Claustrum (Cl) Insula (In) Extreme capsule Column of fornix (ColFor) (ExtrmCap) Third ventricle (ThrVen) Amygdaloid nuclear Column of fornix complex (AmyNu) (ColFor) Optic Tract (OpTr) Amygdaloid nuclear complex (AmyNu) HypothalamusBLatVen BCorCl Body of HCaNu fornix CorRad IntCap AntTub ExtCapAnterior Put In nucleus GP ThrVen Ventral Hyth OpTr anterior ThrVen nucleus AmyNu OpTr Hippo- campus4-3 The rostral surface of a coronal section of brain through the level quately expose the anterior tubercles of the thalamus. The terminal veinof the anterior tubercle of the thalamus and the column of the fornix just cau- is also called the superior thalamostriate vein. The two MRI imagesdal to the anterior commissure. Portions of the columns of the fornix (both are inversion recovery) are at the same plane and show many ofand the septum (drawn in as black lines) were removed to more ade- the structures identified in the brain slice.

Septum Coronal Brain Slice—MRI Correlation 67 Body of fornix (BFor) Body of corpus callosum (BCorCl) Body of lateral ventricle (BLatVen) Anterior nucleus Body of caudate nucleus of thalamus (AntNu) (BCaNu) Ventral anterior nucleus Stria terminalis and of thalamus (VA) terminal vein Posterior limb of Corona radiata (CorRad) internal capsule (PLIntCap)Ventral anterior nucleus Putamen (Put) of thalamus (VA) Insula (In) Mammillothalamic tract Globus pallidus (GP) External capsule Third ventricle (ThrVen) (ExtCap) Amygdaloid nuclear complex (AmyNu) Claustrum Extreme capsule Mammillary body (MB) Hippocampal formation (ExtrmCap) Oculomotor nerve Interpeduncular fossa Dorsomedial nucleus Basilar pons (BP) of thalamus Optic Tract Inferior horn of lateral ventricle (IHLatVen) Hippocampal formation (Hip) Posterior cerebral artery BCorCl BLatVen BCorCl BCaNu BLatVen BFor BFor AntNu AntNu VA VAThalamus PLIntCap Put PLintCap In Put Hip GP MBIHLatVen IHLatVen Hip BP4-4 The rostral surface of a section of brain through the anterior nu- pallidus is clearly divided into its lateral and medial segments in the braincleus of the thalamus, mammillothalamic tract, and mammillary bodies. The slice. Additionally, the terminal vein is also called the superior thala-two MRI images (both are inversion recovery) are at the same plane and mostriate vein.show many of the structures identified in the brain slice.The globus

68 Internal Morphology of the Brain in Slices and MRI Body of fornix (BFor) Body of corpus callosum (BCorCl) Stria terminalis and Body of lateral ventricle (BLatVen) Body of caudate nucleus terminal vein (BCaNu) Corona radiata (CorRad) Dorsomedial nucleus of thalamus (DMNu) Third ventricle and massa intermedia Ventral lateral nucleusPosterior limb of internal of thalamus (VL) capsule (PLIntCap) External capsule Putamen (Put) Claustrum Insula (In) Extreme capsule Internal medullary lamina (IML) Subthalamic nucleus Globus pallidus (GP) Red nucleus Third ventricle (ThrVen) Substantia nigra (SN) Tail of caudate nucleus Inferior horn of Interpeduncular fossa (IPF) lateral ventricle Basilar pons (BP) Hippocampal formation (Hip) Optic tract Crus cerebri (CC) Corticospinal fibers BFor BCorCl BFor BCaNu IML ThrVen DMNu ThrVenPLIntCap SN VL Put In IPF GP Hip Put CC SN IPF BP4-5 The rostral surface of a coronal section of brain through caudal are at the same plane and show many of the structures identified in theparts of the ventral lateral nucleus, the massa intermedia, the subthalamic nu- brain slice. The terminal vein is also called the superior thalamostriatecleus, and basilar pons. The two MRI images (both are inversion recovery) vein.

Coronal Brain Slice—MRI Correlation 69 Body of fornix (BFor) Body of corpus callosum (BCorCl) Stria terminalis and Body of lateral ventricle (BLatVen) terminal vein Body of caudate nucleus (BCaNu) Lateral dorsal nucleus of thalamus Corona radiata Ventral posterolateral Dorsomedial nucleusnucleus of thalamus (VPL) of thalamus (DMNu) Centromedian nucleus Crus Cerebri (CC) Internal medullary of thalamus Substantia nigra lamina (IML) Insula External capsule Ventral posteromedial nucleus of thalamus Claustrum Tail caudate nucleus Inferior horn of lateral Putamen (Put) ventricle (IHLatVen) Third ventricle Posterior limb Interpeduncular fossa (IPF) of internal Trigeminal nerve (TriNr) capsule (PLIntCap) Basilar pons Optic tract Hippocampal formation (Hip) Red nucleus (RNu) BFor BCorCl BLatVen IML BCaNuPLIntCap DMNu VPL RNu Put Hip TriNr CC IPF TriNr BP4-6 The rostral surface of a coronal section of brain through the lat- is at the same plane and shows many of the structures identified in theeral dorsal and centromedian nuclei, rostral midbrain (red nucleus), and cor- brain slice. The terminal vein is also called the superior thalamostriateticospinal fibers in the basilar pons. The MRI image (inversion recovery) vein.

70 Internal Morphology of the Brain in Slices and MRI Body of fornix (BFor) Body of corpus callosum (BCorCl) Body of lateral ventricle (BLatVen) Fimbria of fornix (FFor) Stria terminalis and Body of caudate nucleus (BCaNu) terminal vein Pulvinar (Pul) Pulvinar (Pul) Retrolenticular limb of Medial geniculate internal capsule nucleus (MGNu) Posterior commissure Lateral geniculate Tail of caudate nucleus (LGNu) nucleusInferior horn of lateral Lateral geniculate ventricle (HLatVen) nucleus (LGNu) Hippocampal Pretectal area (PrTecAr) formation (Hip) Periaqueductal gray Middle cerebellar peduncle (MCP) Cerebral aqueduct (CA) Decussation of superior cerebellar peduncle Pyramid BFor BCorCl FFor Pul BLatVen Pul BCaNuLGNu PrTecAr Pul IHLatVenMGNu MGNu LGNu Hip Basilar Basilar pons pons CA Trigeminal nerve4-7 The rostral surface of a coronal section of brain through the pul- same plane and show many of the structures in the brain slices. Thevinar, medial, and lateral geniculate nuclei, the basilar pons, and middle cere- terminal vein is also called the superior thalamostriate vein. For detailsbellar peduncle. The two MRI images (both inversion recovery) are at the of the cerebellum see Figures 2-31 to 2-33 on pp. 32 and 33.

Coronal Brain Slice—MRI Correlation 71 Crus of fornix (CrF) Body of corpus callosum (BCorCl) Fimbria of fornix (FFor)Body of lateral ventricle (BLatVen) Body of caudate Pulvinar (Pul) nucleus (BCaNu) Retrolenticular limb Stria terminalis and of internal capsule terminal vein Pineal Fimbria of hippocampusTail caudate nucleus Hippocampal Inferior horn of lateral formation (Hip) ventricle (IHLatVen) Cerebral aqueduct (CA) Superior colliculus (SC) Medulla (Med) Periaqueductal gray (Pag) Flocculus Middle cerebellar peduncle (MCP) BCorCl FFor SpleniumBLatVen Pul of corpus callosum BLatVen SC SC IHLatVen Hip HipPag CA Pag MCPMed MCP Pyramid4-8 The rostral surface of a coronal section of brain through the pul- tures identified in the brain slice. The terminal vein is also called thevinar nucleus, the superior colliculus, the middle cerebellar peduncle, and the superior thalamostriate vein. For details of the cerebellum see Figuresrostral portion of the medulla oblongata. The two MRI images (both are 2-31 to 2-33 on pp. 32 and 33.inversion recovery) are at the same plane and show many of the struc-

72 Internal Morphology of the Brain in Slices and MRI Towards posterior horn of Splenium of corpus lateral ventricle (PHLatVen) callosum (SpCorCl) Crus of fornix (CrFor) Hippocampal commissure Hippocampal (HipCom) formation Optic RadiationsTowards inferior horn (OpRad) of lateral ventricle (IHLatVen) Tapetum (Tap) Inferior colliculus (IC) Trochlear nerve Superior cerebellar Fourth ventricle (ForVen) peduncle (SCP) Medulla (Med) Middle cerebellar peduncle (MCP) Restiform body Pyramid (Py) CrFor SpCorCl PHLat Ven Tap IHLatVen HipComOpRad SCP Hip MCP IC IC Py ForVen Med4-9 The rostral surface of a coronal section of brain through the sple- of the lateral ventricles. The two MRI images (both are inversion re-nium of corpus callosum, the inferior colliculus, the middle cerebellar pe- covery) are at the same plane and show many of the structures identi-duncle in the base of the cerebellum, and the rostral portion of the fied in the brain slice. For details of the cerebellum see Figures 2-31 tomedulla oblongata. The plane of the section is also through the atrium 2-33 on pp. 32 and 33.

Internal Morphology of the Brain in Slices and MRIBrain Slices in the Axial Plane with MRIOrientation to Axial MRIs: When looking at an axial MRI using MRI (or CT) in the diagnosis of the neurologically impairedimage, you are viewing the image as if standing at the patient’s patient.feet and looking toward his or her head while the patient is lyingon his or her back. Consequently, and as is the case in coronal im- To reinforce this concept, the ventral surface of each axial sliceages, the observer’s right is the left side of the brain in the MRI was photographed. So, when looking at the slice, the observer’sand the left side of the patient’s brain. It is absolutely essential to right is the left side of the brain slice. This view of the slice cor-have a clear understanding of this right-versus-left concept when relates exactly with the orientation of the brain as seen in the ac- companying axial MRIs.

74 Internal Morphology of the Brain in Slices and MRI Corona radiata (CorRad) Body of corpus callosum (toward the genu)Corpus callsoum (CorCl) Caudate nucleus Body of lateral (CaNu) ventricle (BLatVen) Stria terminalis and terminal vein Body of corpus callosum (toward the splenium)CorCl Anterior CorCl forceps CorRad CaNu BLatVen Septum pellucidum Posterior forceps4-10 Ventral surface of an axial section of brain through dorsal por- sion recovery) are at a similar plane and show some of the structurestions of corpus callosum. The plane of the section just touches the upper identified in the brain slice. The terminal vein is also called the superiorportion of the body of caudate nucleus. The two MRI images (both inver- thalamostriate vein.

Cingulate gyrus Axial Brain Slice—MRI Correlation 75 Genu of corpus Anterior cerebral arteries calllosum Head of caudate Anterior horn of lateral nucleus (HCaNu) ventricle (AHLatVen) Body of fornix Stria terminalis and terminal vein Anterior tubercleCorona radiata (CorRad) Anterior nucleus of Lateral thalamic nuclei thalamusDorsomedial nucleus Ventral anterior of thalamus nucleus of thalamusTail of caudate nucleus Tail of caudate nucleus Crus of fornix Lateral ventricle (LatVen) Splenium of corpus callosumLatVen Caudate AHLatVen nucleus HCaNu Putamen Internal capsule CorRad Dorsal Septum thalamus pellucidum Atrium of lateral ventricle4-11 Ventral surface of an axial section of brain through the splenium sion recovery—left; T2-weighted—right) are at a comparable planeof corpus callosum and the head of the caudate nucleus. This plane includes and show some of the structures identified in the brain slice. The ter-only a small portion of the dorsal thalamus. The two MRI images (inver- minal vein is also called the superior thalamostriate vein.

76 Internal Morphology of the Brain in Slices and MRI Anterior horn of lateral Genu of corpus callosum ventricle (AHLatVen) Septum pellucidum Head of caudate nucleus (HCaNu) Stria terminalis and Column of fornix (ColFor) terminal vein Anterior limb of Genu of internal internal capsule (ALIntCap) capsule (GIntCap) Putamen (Put) Anterior nucleus of thalamus Choroid plexus in third ventricle Ventral anterior nucleus of thalamus Insula (In) Third ventricle (ThrVen) Globus pallidus (GP) Internal medullary lamina Dorsomedial nucleus Claustrum of thalamus (DMNu) Posterior limb of internal Habenular nucleus (Hab) capsule (PLIntCap) Retrolenticular limb of Ventral lateral nucleus internal capsule (RLIntCap) of thalamus Tail of caudate nucleus Centromedian nucleus of thalamus Pulvinar (Pul) Ventral posterolateral Crus of fornix nucleus of thalamus Splenium of corpus callosum (SpCorCl) Fimbria of hippocampusHippocampal formation (Hip) Atrium of lateral ventricle (ALatVen) Optic radiations Tapetum Posterior horn of lateral ventricle (PHLatVen) ALIntCap HCaNu AHLatVen Put ALIntCap GIntCap ColFor GIntCapPLIntCapr GP ThrVen PLIntCap Lateral DMNu Lateral thalamic thalamic nuclei Pul nuclei RLIntCap RLIntCap ThrVen ALatVen Hab PHLatVen Hip SpCorCl4-12 Ventral surface of an axial section of brain through the genu of structures identified in the brain slice. The arrowheads in the brain slicethe corpus callosum, head of caudate nucleus, centromedian nucleus, and dor- and in the MRIs are pointing to the mammillothalamic tract. The ter-sal portions of the pulvinar. The two MRI images (inversion recovery— minal vein is also called the superior thalamostriate vein.left; T2-weighted—right) are at the same plane and show many of the

Axial Brain Slice—MRI Correlation 77 Genu of corpus callosum Anterior commissure (AC) Subcallosal gyri Head of caudate nucleus (HCaNu) Anterior limb of internal Column of fornix (ColFor) capsule (ALIntCap) Third ventricle Mammillothalamic tract (MtTr) Putamen (Put) External capsule Claustrum Globus pallidus (GP) Extreme capsule Ventral posterior Insula (In) thalamic nuclei Posterior limb of internal Brachium of superior capsule (PLIntCap) colliculus Pulvinar Subthalamic nucleus Tail of caudate nucleus Red nucleus (RNu) Lateral geniculate Tapetum (Tap) nucleus (LGNu) Optic radiation (OpRad)Retrolenticular limb of Atrium of lateral ventricle internal capsule (ALatVen)Fimbria of hippocampus Posterior horn of lateral ventricle (PHLatVen)Hippocampal formation (Hip) Medial geniculate Superior colliculus (SC) nucleus (MGNu) Pineal Splenium of corpus callosum (SpCorCl) AC ALIntCap HCaNu ColFor Put ColFor In MtTr GP AC Massa MtTrPLIntCap intermed. RNu Pul Hip LGNu Lateral ALatVen MGNu thalamic Tap nuclei SCDorsomedial PHLatVen nucleus Crus of fornix OpRadSpCorCl4-13 Ventral surface of an axial section of brain through the anterior can be discerned on the right side of the brain. The MRI images (bothcommissure, column of fornix, medial and lateral geniculate nuclei, and supe- T2-weighted) are at approximately the same plane and show many ofrior colliculus. The medial and lateral segments of the globus pallidus are vis- the structures identified in the brain slice.ible on the slice. The lateral and medial segments of the globus pallidus

78 Internal Morphology of the Brain in Slices and MRI Hypothalamus (HyTh) Anterior cerebral arteries (ACA) Head of Lamina terminalis caudate nucleus Third ventricle (ThrVen) Nucleus accumbens Optic tract (OpTr) Anterior perforated Uncus substance Amygdaloid Crus cerebri (CC) nuclear complex Inferior horn of lateral ventricle Mammillary body (MB) Interpeduncular (IHLatVen) fossa (IPF) Lateral geniculate Hippocampal nucleus formation Tail of caudate nucleus Substantia Hippocampal formation (Hip) nigra (SN) Choroid plexus in inferior hornDecussation of superior cerebellar peduncle Periaqueductal gray Inferior colliculus (IC) Cerebral Aqueduct (CA) Cerebellum (Cbl)ThrVen OpTr ACA Un HyTh ThrVen SN MB CC IHLatVen IC IPF Hip Cbl CA Posterior horn lateral ventricle Posterior cerebral artery4-14 Ventral surface of an axial section of brain through the hypo- planes and show many of the structures identified in the brain slice. Forthalamus, mammillary body, crus cerebri, and inferior colliculus. The two MRI details of the cerebellum see Figures 2-31 to 2-33 on pp. 32 and 33.images (inversion recovery—left; T2-weighted—right) are at similar

Corticospinal fibers Axial Brain Slice—MRI Correlation 79 Medial lemniscus (ML) Basilar artery (BA) Tegmentum of pons (TegP) Basilar pons (BP) Superior cerebellar Fourth ventricle (ForVen) peduncle (SCP) Nucleus coeruleusHemisphere of anterior lobe Vermis of anterior lobe of cerebellum (HCbl) of cerebellum (VCbl) Hemisphere of posterior lobe of cerebellum HCbl BA Temporal VCbl lobe BPOccipital ML HCbl lobe TegP SCP VCbl Occipital ForVen lobe4-15 Ventral surface of an axial section of brain through rostral plane and show many of the structures identified in the brain slice. Forparts of the basilar pons and the anterior lobe of the cerebellum. The two MRI details of the cerebellum see Figures 2-31 to 2-33 on pp. 32 and 33.images (T2-weighted—left; inversion recovery—right) are at the same

80 Internal Morphology of the Brain in Slices and MRI Medial lemniscus Basilar artery (BA) Tegmentum of pons (TegP) Basilar pons (BP) Trigeminal nerve (TriNr) Dentate nucleus (DNu)Hemisphere of posterior lobe Middle cerebellar peduncle (MCP) of cerebellum (HCbl) Fourth ventricle (ForVen) Vermis of posterior lobe of cerebellum (VCbl) BP Temporal BA TriNr lobe Temporal lobe MCP TrigeminalForVen ganglion BP TegP HCbl TriNr ForVen Lesion in BP TegP BP BA MCP TegP DNu ForVen VCbl4-16 Ventral surface of an axial section of brain through the middle lower) are at the same planes and show many of the structures identi-regions of the basilar pons, the exit of the trigeminal nerve, the fourth ventri- fied in the brain slice. Note the lesion in the basilar pons (upper right).cle, and the cerebellar nuclei. The three MRI images (inverted inversion For details of the cerebellum see Figures 2-31 to 2-33 on pp. 32recovery—upper left; T2-weighted—upper right; T1-weighted— and 33.

Axial Brain Slice—MRI Correlation 81 Basilar pons Basilar artery Pyramid (Py) Anterior median fissure (AMF) Olivary eminence (OlEm) Preolivary sulcus (PreOIS) Vagus and glossopharyngeal Vestibulocochlear nerve nerves Retroolivary sulcus (Postolivary sulcus) (PoOIS) Restiform body (RB) Medial lemniscusTonsil of cerebellum (TCbl) Fourth ventricle (ForVen)Hemisphere of posterior lobe of cerebellum (HCbl) Vermis of posterior lobe of cerebellum (VCbl)PreOlS AMF TCbl PoOlS Py OlEm TCbl RB HCbl ForVen VCbl OlEm Lesion-Lateral RB medullary syndrome ForVen4-17 Ventral surface of an axial section of brain through portions of show many of the structures identified in the brain slice. Note the lateralthe medulla oblongata, just caudal to the pons–medulla junction and the medullary lesion (lower), also known as the posterior inferior arteryposterior lobe of the cerebellum. The three MRI images (T1-weighted— syndrome or the lateral medullary syndrome (of Wallenberg). For de-upper left and right; T2-weighted—lower) are at the same plane and tails of the cerebellum see Figures 2-31 to 2-33 on pp. 32 and 33.

CHAPTER 5Internal Morphology of the Spinal Cord and Brain in Stained SectionsBasic concepts that are essential when one is initially learning how and the lateral corticospinal tract (grey). In the brainstem, theseto diagnose the neurologically impaired patient include 1) an un- spinal tracts are joined by the spinal trigeminal tract and ventralderstanding of cranial nerve nuclei and 2) how these structures re- trigeminothalamic fibers (both are light green). The long tracts arelate to long tracts. The importance of these relationships is clearly color-coded on one side only, to emphasize 1) laterality of functionseen in the combinations of deficits that generally characterize le- and dysfunction, 2) points at which fibers in these tracts may de-sions at different levels of the neuraxis. First, deficits of only the cussate, and 3) the relationship of these tracts to cranial nerves.body that may present as motor or sensory losses (long tracts) onthe same, or opposite, sides are indicative of spinal cord lesions A color key appears on each page. This key identifies the var-(e.g., Brown-Sequard syndrome). Spinal cord injuries character- ious tracts and nuclei by their color and specifies the function ofistically have motor and sensory levels; these are the lowest functional each structure on each page. This approach not only emphasizeslevels remaining in the compromised patient. Second, cranial anatomical and clinical concepts, but also lends itself to a varietynerve deficits (on one side of the head) in combination with long of instructional settings.tract signs (on the opposite side of the body) characterize lesionsin the brainstem (e.g., lateral medullary or Weber syndromes). Correlation of MRI and CT with Spinal Cord andThese patterns of loss are frequently called alternating or crosseddeficits. In these examples cranial nerve signs are better localizing Brainstem: As one is learning basic anatomical concepts it issigns than are long tract signs. A localizing sign can be defined as an essential to consider how this information may be used in theobjective neurologic abnormality that correlates with a lesion (or clinical environment. To this end, MRI (T1- and T2-weighted)lesions) at a specific neuroanatomical location (or locations). and CT (myelogram/cisternogram) images are introduced intoThird, motor and sensory deficits on the same side of the head and the spinal cord and brainstem sections of this chapter (see alsobody are usually indicative of a lesion in the forebrain. Chapter 1). To show the relationship between basic anatomy and how MRI and CT are viewed, a series of self-explanatory illus- Color Coded Cranial Nerve Nuclei and Long Tracts: trations are provided on each set of facing pages in these sections. This continuum of visual information consists of (1) a small ver-Cranial nerve nuclei are coded by their function: pink, sensory; sion of the colorized line drawing in an Anatomical Orientation,red, motor. These structures are colored bilaterally to make it easy (2) a top-to-bottom flip of this illustration that brings it into ato correlate cranial nerve and long tract function on both sides of Clinical Orientation, and (3) a CT (spinal cord) or MRI and CTthe midline. For example, one can easily correlate damage to the (brainstem) that follows this clinically oriented image. Every ef-hypoglossal nerve root and the adjacent corticospinal fibers on one fort is made to identify and use MRI and CT that correlate, asside while comparing this pattern with the clinical picture of a lat- closely as possible, with their corresponding line drawing anderal medullary syndrome on the other side. stained section. This approach recognizes and retains the strength of the anatomical approach, introduces essential clinical Long tracts are color-coded beginning at the most caudal spinal concepts while at the same time allowing the user to customizecord levels (e.g., see Figures 5-1 and 5-2), with these colors ex- the material to suit a range of educational applications.tending into the dorsal thalamus (see Figure 5-30) and the posteriorlimb of the internal capsule (see Figures 5-31 and 5-32). The col- *The dark and light blue colors represent information originating from lowerorized spinal tracts are the fasciculus gracilis (dark blue), the fasci- and upper portions of the body, respectively.culus cuneatus (light blue)*, the anterolateral system (dark green),

5-1 Transverse section of the spinal cord showing the character- 84 Internal Morphology of the Spinal Cord and Brain in Stained Sections istics of a sacral level. The gray matter occupies most of the cross- section; its H-shaped appearance is not especially obvious at sacral–coccygeal levels. The white matter is a comparatively thin mantle. The sacral cord, although small, appears round in the CT myelogram. Note the appearance of the sacral spinal cord sur- rounded by the upper portion of the cauda equina (left) and the cauda equina as it appears caudal to the conus medullaris in the lumbar cis- tern (right). Compare with Figure 2-4 on page 12. Substanita gelatinosa (lamina II) Gracile fasciculus Dorsolateral tractNucleus proprius (laminae III,IV) Posteromarginal nucleus (lamina I)Intermediate zone (lamina VII) Lateral corticospinal tract Lateral motor nuclei (lamina IX) Propriospinal fibers (ProSp) Medial motor nuclei (lamina IX) Anterolateral system Post. column/med. lemniscus sys. (proprioception/vibratory sense, Reticulospinal tract discriminative touch) ProSp Corticospinal fibers Anterolateral system (somatomotor) (pain/thermal sense, touch from body)

Lumbar cistern Cauda equina Sacral spinal cord Anatomical orientation Clinical orientation CT myelogram CT myelogramAnatomical orientation Clinical orientation CT myelogram CT myelogram The Spinal Cord With CT 85

5-2 Transverse section of the spinal cord showing its characteristic 86 Internal Morphology of the Spinal Cord and Brain in Stained Sections appearance at lumbar levels (L4). Posterior and anterior horns are large in relation to a modest amount of white matter, and the general shape of the cord is round. Fibers of the medial division of the posterior root directly enter the gracile fasciculus. The lumbar spinal cord appears round in the CT myelogram. The roots of upper portions of the cauda equina surround the lower levels of the lumbar spinal cord (right). ProSp Posterior median sulcus Gracile fasciculusMedial division fibers Dorsolateral tract Posteromarginal nucleus (lamina I) Lateral corticospinal tract Substanita gelatinosa (lamina II) Rubrospinal tractNucleus proprius (laminae III,IV) Propriospinal fibers (ProSp) Area of lamina V Area of lamina VI Intermediate zone (lamina VII) Anterolateral systemLateral motor nuclei (lamina IX) Area of lamina VIII Medullary (lateral)Medial motor nuclei (lamina IX) reticulospinal fibers ProSp Lateral vestibulospinal tract and pontoreticulospinal (Medial reticulospinal) tract Anterior root fibers Medial longitudinal fasciculus Anterior corticospinal tract Anterior median fissurePost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system(proprioception/vibratory sense, (somatomotor) (pain/thermal sense,discriminative touch) touch from body)

Anterior root Lumbar spinal cord Posterior root Cauda equinaAnatomical orientation Clinical orientation CT myelogram CT myelogram The Spinal Cord With CT 87

5-3 Transverse section of the spinal cord showing its characteristic 88 Internal Morphology of the Spinal Cord and Brain in Stained Sections appearance at thoracic levels (T4). The white matter appears large in relation to the rather diminutive amount of gray matter. Posterior and anterior horns are small, especially when compared to low cervical lev- els and to lumbar levels. The overall shape of the cord is round. The thoracic spinal cord appears round in CT myelogram. Posterior median sulcus ProSp Gracile fasciculus Posterolateral sulcus Posterior intermediate sulcus Dorsolateral tract Cuneate fasciculus Posteromarginal nucleus and Medial division fiberssubstantia gelatinosa (laminae I,II) of posterior root Nucleus proprius Posterior spinocerebellar tract (laminae III,IV) Lateral corticospinal tract Dorsal thoracic nucleus Rubrospinal tract of Clarke (lamina VII) Propriospinal fibers (ProSp)Intermediolateral cell column Anterior spinocerebellar tract (lamina VII) Medullary (lateral) reticulospinal tract Medial motor nuclei (lamina IX) Anterior root fibers Anterolateral system Spino-olivary fibersLateral vestibulospinal tract Medial longitudinal fasciculus Pontoreticulospinal tract Anterior corticospinal tract ProSp Anterior white commissure Anterior median fissurePost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system(proprioception/vibratory sense, (somatomotor) (pain/thermal sense,discriminative touch) touch from body)

Anterior root Posterior rootAnatomical orientation Clinical orientation CT myelogram CT myelogram The Spinal Cord With CT 89

5-4 Transverse section of the spinal cord showing its characteristic 90 Internal Morphology of the Spinal Cord and Brain in Stained Sections appearance at lower cervical levels (C7). The anterior horn is large, and there is—proportionally and absolutely—a large amount of white matter. The overall shape of the cord is oval. The lower portions of the cervical spinal cord appears oval in MRI (left) and in CT myelogram (center and right). Posterior median sulcus Interfascicular fasciculus Gracile fasciculus Dorsolateral tract Posterior intermediate sulcusPosteromarginal nucleus (lamina I) Cuneate fasciculus Posterolateral sulcus Substantia gelatinosa (lamina II) Posterior spinocerebellar tract Lateral corticospinal tractNucleus proprius (laminae III, IV) Reticular nucleus of cervical cord Area of lamina V Propriospinal Area of lamina VI fibers (ProSp)Intermediate Zone (lamina VII) Rubrospinal tract Anterior spinocerebellar tractLateral motor nuclei Medullary (lateral) (lamina IX) reticulospinal tract Area of lamina VIII Anterolateral system Medial motor nuclei (lamina IX) Spino-olivary fibers ProSp Anterolateral sulcus Anterior white commissure Lateral vestibulospinal tract Anterior corticospinal tract Pontoreticulospinal (medial reticulospinal) tract Medial longitudinal fasciculus Anterior median fissure and tectospinal tractPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system(proprioception/vibratory sense, (somatomotor) (pain/thermal sense,discriminative touch) touch from body)

Anatomical orientation Clinical orientation MRI, T2 weighted image CT myelogram CT myelogram The Spinal Cord With CT 91

ProSp 5-5 Transverse section of the spinal cord at the C1 level. Lateral 92 Internal Morphology of the Spinal Cord and Brain in Stained Sections corticospinal fibers are now located medially toward the decussation of Spinal trigeminal tract and the corticospinal fibers, also called the motor decussation or pyramidal Dorsolateral tract junction decussation (see also Figure 5-8, page 98). At this level, fibers of the spinal trigeminal tract are interdigitated with those of the dorsolateral Gelatinosa portion of tract. The spinal cord at C1 and C2 levels appear round in CT myelo- Spinal trigeminal nucleus gram when compared to low cervical levels (see Figure 5-4). Magnocellular portion of Posterior median sulcusSpinal trigeminal nucleus Gracile fasciculus Posterior intermediate sulcus Cuneate fasciculus Lateral corticospinal tract Posterior spinocerebellar tractSpinal accessory nucleus Rubrospinal tractSpino-olivary fibers Propriospinal Medial motor nuclei fibers (ProSp) ProSp Anterior spinocerebellar tract Anterior corticospinal tract Pyramidal decussation Medullary (lateral) reticulospinal tract Tectospinal tract Anterolateral system Anterolateral system (pain/thermal sense, Lateral vestibulospinal tract touch from body) Pontoreticulospinal (Medial reticulospinal) tract Medial longitudinal fasciculusPost. column/med. lemniscus sys. Corticospinal fibers Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) trigeminothalamic fibers (pain/ Motor nervediscriminative touch) thermal sense, touch from head) nuclei

Posterior rootAnatomical orientation Clinical orientation CT myelogram CT myelogram The Spinal Cord With CT 93

Vascular Syndromes or Lesions of the Spinal Cord 94 Internal Morphology of the Spinal Cord and Brain in Stained Sections Acute Central Cervical Spinal Cord Syn- congenital vascular lesions. Symptoms may develop over the shoulder and upper extremities). The other commonly seen rapidly or gradually in stepwise fashion, and blood is deficit results from extension of the cavity into the anterior horn(s).drome: Results from occlusion of the anterior usually present in the cerebrospinal fluid. The result is unilateral or bilateral paralysis of the upper extremities (cervi-spinal artery. cal levels) or lower extremities (lumbosacral levels) due to damage to the Arteriovenous malformation in spinal cord: anterior motor neuron cells. This paralysis is characteristically a lowerDeficit Structure Damage motor neuron deficit. A syrinx in the spinal cord, particularly in cervi- More frequently found in lower cord levels. Symptoms cal levels, may be associated with a variety of other developmental de-• Bilateral paresis or • Medial portions of both (micturition problems are seen early, motor deficits, lower fects in the nervous system. back pain) may appear over time and may seem to re-flaccid paralysis of lateral corticospinal solve then recur (get better then worse). These lesions Spinal Cord Lesions: A complete spinal cord lesion is characterized are usually found external to the cord (extramedullary) by a bilateral and complete loss of motor and sensory function belowupper extremities tracts; ventral grey and can be surgically treated, especially when the ma- the level of lesion persisting for more than 24 hours. The vast majority jor feeding vessels are few in number and easily identi- of the patients with complete lesions (95%+) will suffer some perma- horns at cervical levels fied. Foix-Alajouanine syndrome is an inflammation of nent deficits. Incomplete spinal cord lesions are those with preservation of spinal veins with subsequent occlusion that results in sacral cord function at presentation. The above described cases are ex-• Irregular loss of pain • Anterolateral system infarct of the spinal cord and a necrotic myelitis. The amples of incomplete spinal cord lesions. symptoms are ascending pain and a flaccid paralysis.and temperature sensa- fibers (partial Brown-Sequard syndrome: This syndrome istions bilaterally over involvement a hemisection of the spinal cord that may result from trauma, compression of the spinal cord by tumors orbody below lesion bilaterally) hematomas, or significant protrusion of an interver- tebral disc. The deficits depend on the level of theComment: Hyperextension of the neck may causative lesion. The classic signs are (1) a loss of pain and thermal sensation on the contralateral side of thecause damage to the vertebral arteries (which give body beginning about 1–2 segments below the level of the lesion (damage to anterolateral system fibers), (2)rise to the anterior spinal artery), or it may directly a loss of discriminative touch and proprioception on the ipsilateral side of the body below the lesion (in-damage the anterior spinal artery, causing a spasm. terruption of posterior column fibers), and (3) a paralysis on the ipsilateral side of the body below the lesionThis vascular damage leads to a temporary or perma- (damage to lateral corticospinal fibers). This syndrome is classified as an incomplete spinal cord injury (see below)nent interruption of blood supply. Deficits may re- and the majority of patients with this lesion will re- 5-6 Semidiagrammatic representation of the internal blood supply gain some type of motor and sensory function. Com- to the spinal cord. This is a tracing of a C4 level, with the positions ofsolve within a few hours or may be permanent, de- pression of the spinal cord may result in some, but not principal tracts superimposed on the left and the general pattern of all, of the signs and symptoms of the syndrome. blood vessels superimposed on the right.pending on the extent of vascular complication. Syringomyelia: This condition is cavitation ofSparing of the dorsal columns (proprioception, vibra- central portion of the spinal cord. A cavitation of the central canal with an ependymal cell lining is hy-tory sense) is a hallmark; approximately the anterior dromyelia. A syrinx may originate in central portions of the spinal cord, may communicate with the centraltwo-thirds of the spinal cord is ischemic. canal, and is most commonly seen in cervical levels of the spinal cord. The most common deficits are a bi-Thrombosis of Anterior Spinal Artery: This lateral loss of pain and thermal sensation due to damage to the anterior white commissure: the loss reflects the levelsmay occur in a hypotensive crisis, as a result of trauma of the spinal cord damaged (e.g., a cape distribution Abbreviationsresulting from a dissecting aortic aneurysm, or in pa-tients with atherosclerosis. It may occur at all spinal A Representation of arm fibers AH Anterior (ventral) hornlevels but is more frequently seen in thoracic and lum- AWCom Anterior white commissure CenC Central canalbosacral levels unless trauma is the primary cause. Re- IZ Intermediate zone Representation of leg fiberssults are bilateral flaccid paraplegia (if lesion is below cer- L Representation of neck fibers N Posterior (dorsal) hornvical levels) or quadriplegia (if lesion is in cervical PH Representation of sacral fibers S Representation of truck fiberslevels), urinary retention, and loss of pain and temperature Tsensation. Flaccid muscles may become spastic over aperiod of a day to weeks, with hyperactive deep tendon re-flexes and extensor plantar (Babinski) reflexes. In addition,lesions at high cervical levels may also result in paraly-sis of respiratory muscles. The artery of Adamkiewicz(an especially large spinal medullary artery) is usuallylocated at spinal levels T12–L1 and more frequentlyarises on the left side. Occlusion of this vessel may in-farct lumbosacral levels of the spinal cord.Hemorrhage in the spinal cord: This is rarelyseen but may result from trauma or bleeding from