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

Fasciculus gracilis AVC Fasciculus cuneatus Dorsolateral tract Posterior spinal artery Arterial Patterns Within The Spinal Cord With Vascular Syndromes 95Lateral corticospinal tract Posterior spinal medullary artery Propriospinal fibers PH L Arterial Posterior radicularPosterior spinocerebellar tract T vasocorona artery to posterior root AWCom A (AVC) Rubrospinal tract CenC Segmental IZ S artery L Anterior radicular arteryAnterior spincerebellar tract T to anterior root A AH NAnterolateral system Reticulospinal and Anterior spinal medullary arteryvestibulospinal tracts Medial longitudinal fasciculus and anterior cortocospinal tract Sulcal artery Anterior spinal artery

5-7 All of the brainstem sections used in Figures 5-9 through 5-13 96 Internal Morphology of the Spinal Cord and Brain in Stained Sections(medulla), 5-17 through 5-20 (pons), and 5-22 through 5-25 (mid-brain) are from an individual who had an infarct (green in drawing) inthe posterior limb of the internal capsule. This lesion damaged corti-cospinal fibers (grey in drawing), resulting in a contralateral hemiple-gia of the arm and leg, and damaged sensory radiations that travel fromthalamic nuclei to the somatosensory cortex through the posterior limbof the internal capsule. Although the patient survived the initialepisode, corticospinal fibers (grey) distal to the lesion (green) under-went degenerative changes and largely disappeared. This Wallerian(anterograde) degeneration takes place because the capsular infarct ef-fectively separates the descending corticospinal fibers from their cellbodies in the cerebral cortex. Consequently, the location of corti-cospinal fibers in the middle one-third of the crus cerebri of the mid-brain, in the basilar pons, and in the pyramid of the medulla is charac-terized by the obvious lack of myelinated axons in these structureswhen compared to the opposite side. In the brainstem, these degener-ated fibers are ipsilateral to their cells of origin but are contralateral totheir destination in the spinal cord—hence, the contralateral motordeficit. These photographs give the user the unique opportunity of see-ing where corticospinal fibers are located at all levels of the humanbrainstem. Also, one is constantly reminded of 1) the relationship ofcorticospinal fibers to other structures, 2) the deficits one can expectto see at representative levels due to this lesion, and 3) the general ap-pearance of degenerated fibers in the human central nervous system.These images can be adapted to a wide range of instructional formats.

Degenerated Motor cortex Degenerated Corticospinal Tract 97 corticospinal (precentral gyrus) fibers Internal capsule, posterior limbDegeneratedcorticospinal Infarct in internal capsule fibers Midbrain Pons Medulla Spinal cord

5-8 Transverse section of the medulla through the decussation of the 98 Internal Morphology of the Spinal Cord and Brain in Stained Sections pyramids (motor decussation, pyramidal decussation, crossing of corti- cospinal fibers). This is the level of the spinal cord–medulla transition. The corticospinal fibers have moved from their location in the lateral fu- niculus to the motor decussation and will cross to form the pyramid on the opposite side. Central gray Gracile fasciculusSpinal trigeminal tract Gracile nucleus Cuneate fasciculus Cuneate nucleusSpinal trigeminal nucleus (pars caudalis) Spinal trigeminal tract Gelantinosa Magnocellular Pyramidal decussation Reticulospinal fibers Rubrospinal tract Accessory nucleus Posterior spinocerebellar tract Medial longitudinal Anterolateral system fasciculus Anterior spinocerebellar tract Medial motor nuclei Tectospinal tract Vestibulospinal tract and reticulospinal tract Spino-olivary fibers Anterior corticospinal tract PyramidPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 99

5-9 Transverse section of the medulla through the dorsal column nu- 100 Internal Morphology of the Spinal Cord and Brain in Stained Sections clei (nucleus gracilis and nucleus cuneatus), caudal portions of the hy- poglossal nucleus, caudal end of the principal olivary nucleus, and middle portions of the sensory decussation (crossing of internal arcuate fibers). Central gray Dorsal motor nucleus of vagus Gracile nucleus Posterior longitudinal fasciculus Gracile fasciculus Solitary nuclei and tract Cuneate fasciculus Hypoglossal nucleusCuneate nucleus Accessory cuneate nucleus Posterior spinocerebellar Restiform body tract Internal arcuate fibers Spinal trigeminal tract Rubrospinal tract Spinal trigeminal nucleus Anterior spinocerebellar tract Retroolivary sulcus (pars caudalis) (postolivary sulcus) Nucleus ambiguus Anterolateral systemFascicles of hypoglossal nerve Principal olivary nucleusVentral trigeminothalamic tract Preolivary sulcusLateral reticular nucleus Pyramid Degenerated corticospinal fibers Vestibulospinal fibers Medial longitudinal fasciculus Tectospinal tract and reticulospinal fibers Medial lemniscus Hypoglossal nervePrincipal olivary nucleus Arcuate nucleusMedial accessory olivary nucleusPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 101

5-10 Transverse section of the medulla through rostral portions of 102 Internal Morphology of the Spinal Cord and Brain in Stained Sections the sensory decussation (crossing of internal arcuate fibers), obex, and the caudal one-third of the hypoglossal and principal olivary nuclei. Level of obex Area postrema Posterior longitudinal fasciculus Gracile nucleus Hypoglossal nucleus Dorsal motor nucleus of vagus Cuneate fasciculusCuneate nucleus Solitary nuclei and tractAccessory cuneate nucleus Restiform body Nucleus ambiguus (+ juxtarestiform body= inferior cerebellar peduncle) Spinal trigeminal tract Internal arcuate fibers Spinal trigeminal nucleus Anterior spinocerebellar tract (pars interpolaris) Rubrospinal tract Anterolateral systemLateral reticular nucleus Reticular formation Hypolossal fibers Posterior accessory olivary nucleusRetroolivary sulcus Central tegmental tract(postolivary sulcus) and amiculum of olive Olivocerebellar fibersPrincipal olivary nucleusVentral trigeminothalamic tract Pyramid Preolivary sulcus Medial accessory olivary nucleus Arcuate nucleus Degenerated corticospinal fibers Nucleus raphe, obscurus Medial longitudinal fasciculus Tectospinal tract Medial lemniscusPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 103

5-11 Transverse section of the medulla through rostral portions of 104 Internal Morphology of the Spinal Cord and Brain in Stained Sections the hypoglossal nucleus and the middle portions of the principal olivary nu- cleus. The fourth ventricle has flared open at this level, and the resti- form body is enlarging to become a prominent structure on the dorso- lateral aspect of the medulla. Nucleus raphe, obscurus Posterior longitudinal fasciculus Solitary nuclei and tract Dorsal motor nucleus Hypoglossal nucleus Spinal trigeminal nucleus of the vagus Sulcus limitans (pars interpolaris) Medial Spinal trigeminal tract vestibular nucleus Inferior (spinal) vestibular nucleus Accessorycuneate nucleus Restiform body Reticular formation ( + Juxtarestiform body =Inferior cerebellar peduncle)Nucleus ambiguus Rubrospinal tract Vagus nerve Lateral reticular nucleus Anterior spinocerebellar tract Anterolateral systemPosterior accessory Central tegmental tract olivary nucleus and amiculum of olivePrincipal olivary nucleus Olivocerebellar fibers PyramidHypoglossal nerveVentral trigeminothalamic tract Medial accessory olivary nucleus Arcuate nucleus Degenerated corticospinal fibers Nucleus raphe, pallidus Medial longitudinal fasciculus Tectospinal tract Medial lemniscusPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 105

Cerebellum Nucleus raphe, obscurus 5-12 Transverse section of the medulla through the posterior (dor- 106 Internal Morphology of the Spinal Cord and Brain in Stained Sections sal) and anterior (ventral) cochlear nuclei and root of the glossopharyngeal Inferior salivatory nucleus nerve. This corresponds to approximately the rostral third to fourth of Solitary nuclei the principal olivary nucleus. Solitary tract Posterior longitudinal fasciculusPosterior (dorsal) Nucleus preposituscochlear nucleus Medial vestibular nucleus Stria medullares of fourth ventricle Inferior (or spinal) vestibular nucleus Anterior (ventral) cochlear nucleus Posterior (dorsal) cochlear nucleus Restiform bodyAnterior (ventral) Reticular formationcochlear nucleus Pyramid Pontobulbar nucleus Cochlear nerve Spinal trigeminal tract Glossopharyngeal Spinal trigeminal nucleus (pars oralis) Rubrospinal tract nerve Nucleus ambiguus Anterolateral system Anterior spinocerebellar tract Reticulospinal fibers Central tegmental tract and amiculum of olive Posterior accessory olivary nucleus Olivocerebellar fibers Principal olivary nucleus Degenerated corticospinal fibers Ventral trigeminothalamic tract Medial accessory olivary nucleus Nucleus raphe, pallidus Arcuate nucleus Medial longitudinal fasciculus Tectospinal tract Medial lemniscusPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 107

Posterior longitudinal fasciculus 5-13 Transverse section of the medulla–pons junction through the 108 Internal Morphology of the Spinal Cord and Brain in Stained Sections rostral pole of the principal olivary nucleus and through the facial motor nucleus. This plane is just caudal to the main portions of the abducens nucleus. Pontine nuclei at this level may also be called arcuate nuclei. Superior medullary velum Superior Juxtarestiform body Inferior cerebellar Restiform body cerebellar peduncle peduncleSuperior vestibular nucleus Medial longitudinal fasciculus Medial vestibular nucleus Nucleus raphe, obscurus Lateral vestibular nucleus Solitary nuclei and tract Reticular formation Abducens nucleus Solitary tractSpinal trigeminal nucleus Facial nerve (pars oralis) Facial nucleus Anterior (ventral) Rubrospinal tract cochlear nucleus Vestibular root of VIIIth nerve Pontobulbar nucleus (or body)Spinal trigeminal tract Medial Anterior spinocerebellar Secondary cochlear fibers lemniscus tract Superior olive Tectospinal tract Pyramid Anterolateral system Ventral trigeminothalamic tract Superior olive Principal olivary nucleus Secondary cochlear fibers Nucleus raphe, magnus Central tegmental tract Nucleus raphe, pallidus Pontine nuclei Degenerated corticospinal fibersPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Medulla Oblongata With MRI and CT 109

Vascular Syndromes or Lesions of the Medulla Oblongata 5-14 Semidiagrammatic representation of the internal distribution 110 Internal Morphology of the Spinal Cord and Brain in Stained Sections of arteries in the medulla oblongata. Selected main structures are la- Medial Medullary Syndrome: Results from oc- • Ipsilateral Horner • Descending beled primarily on the left side of each section and the general patternclusion of branches of anterior spinal artery. syndrome (miosis, hypothalamospinal of arterial distribution overlies these structures on the right side. The ptosis, anhidrosis, fibers general distribution patterns of arteries in the medulla as illustrated Deficits Structure Damaged flushing of face) here may vary from patient to patient. For example, the territories • Vestibular nuclei served by adjacent vessels may overlap to differing degrees at their• Contralateral hemiplegia • Pyramid (cortico- • Nausea, diplopia, (mainly inferior and margins or the territory of a particular vessel may be smaller or larger of arm and leg spinal fibers) tendency to fall to medial) than seen in the typical pattern. ipsilateral side,• Contralateral loss of • Medial lemniscus nystagmus, vertigo • Restiform body and Abbreviations position sense, vibratory spinocerebellar fibers sense and discriminative • Hypoglossal nerve in • Ataxia to the touch medulla or hypo- ipsilateral side glossal nucleus• Deviation of tongue to Comment: In addition to the above, involvement of FCu Cuneate fasciculus ipsilateral side when the solitary tract and nucleus may (rarely) cause dysageu- FGr Gracile fasciculus protruded; muscle sia. Dyspnea and tachycardia may be seen in patients with ML Medial lemniscus atrophy and fasciculations damage to the dorsal motor nucleus of the vagus. It is also NuCu Cuneate nucleus possible that damage to respiratory centers in the reticu- NuGr Gracile nucleus Comment: The medial medullary syndrome is rare lar formation or to the vagal motor nucleus may result Pyramidcompared to the more common occurence of the lateral in hiccup (singultus). Bilateral medullary damage may Py Restiform body (ϩ juxtarestiform body ϭmedullary syndrome. Nystagmus may result if the lesion cause the syndrome of “Ondine’s curse,” an inability to RB inferior cerebellar peduncle)involves the medial longitudinal fasciculus or the nu- breathe without willing it or “thinking about it.” Reticular formationcleus prepositus hypoglossi. The lesion may involve RetFventral trigeminothalamic fibers, but diminished pain Tonsillar Herniation: Although the cerebellar ton-and thermal sense from the contralateral side of the face sil is not part of the medulla, the herniation of this struc-is rarely seen. The combination of a contralateral hemi- ture (tonsillar herniation) down through the foramenplegia and ipsilateral deviation of the tongue is called an magnum has serious consequences for function of theinferior alternating hemiplegia when the lesion is at this medulla. The coneing of the cerebellar tonsils into, andlevel. through, the foramen magnum may compress the medulla resulting in cardiac and respiratory arrest. This is Lateral Medullary Syndrome: Results from oc- due to a combination of pressure on the medulla and theculsion of posterior inferior cerebellar artery or occlusion of small vessels serving cardiac and respiratorybranches of PICA to dorsolateral medulla (PICA syn- centers in the lateral area of the medulla. Patients expe-drome, Wallenberg syndrome). In many cases the lat- riencing a sudden herniation of the cerebellar tonsilseral medullary syndrome frequently results from occlu- may lose consciousness rapidly and die.sion of the vertebral artery with consequent loss of flowinto PICA. Syringobulbia: A cavitation within the brainstem (syringobulbia) may exist with syringomyelia, be inde- Deficits Structure Damaged pendent of syringomyelia, or in some cases both may ex- ist and communicate with each other. The cavity in sy-• Contralateral loss of • Anterolateral system ringobulbia is usually on one side of the midline of the medulla. Signs and symptoms of syringobulbia may in-pain and thermal fibers clude weakness of tongue muscles (hypoglossal nucleus or nerve), weakness of pharyngeal, palatal, and vocal muscula-sense on body ture (ambiguus nucleus), nystagmus (vestibular nuclei), and loss of pain and thermal sensation on the ipsilateral side• Ipsilateral loss of pain • Spinal trigeminal of the face (spinal trigeminal tract and nucleus or cross- ing of trigeminothalamic fibers).and thermal sense on face tract and nucleus• Dysphagia, soft palate • Nucleus ambiguus,paralysis, hoarseness, roots of 9th and 10thdiminished gag nervesreflex

Vestibular nuclei Solitary nuclei and tract Nucleus prepositus Posterior (dorsal) cochlear nucleus Medial longitudinal fasciculus Fourth ventricle Spinal trigeminal tract Rostral and nucleus Anterolateral system Inferior olivary complex RetF Arterial Patterns Within The Medulla Oblongata With Vascular Syndromes 111 Hypoglossal nucleus ML Dorsal motor nucleus of vagus Corticospinal fibers Solitary nuclei and tract RB Inferior olivary complex Nucleus ambiguus (principal nucleus) Caudal Spinal trigeminal tract and nucleus Hypoglossal nerve RetF Anterolateral system Solitary nuclei and tract Hypoglossal nucleus NuGr NuCu Internal arcuate fibers Spinal trigeminal tract Nucleus ambiguus and nucleus FCu Posterior spino- FGr cerebellar tract Medial lemniscus (ML)Lateral cortico- Py Pyramid (Py)spinal tract Posterior spino- cerebellar tract Anterolateral Medial decussation Anterior spinal artery system Posterior spinal artery (and arterial vasocorona in spinal cord) Pyramidal decussationRubrospinal Anterolateral system Vertebral arterytract Posterior inferior cerebellar artery Anterior inferior cerebellar artery Vertebral artery plus paramedian branches of caudal portions of basilar artery

5-15 Transverse section through the dorsal aspects of and caudal portions of the globosus and emboliform nuclei. For ad- 112 Internal Morphology of the Spinal Cord and Brain in Stained Sections medulla at the level of the cochlear nuclei and the cerebellar nuclei. ditional details of the medulla at this level see figure 5-12 on page The plane corresponds to about the middle of the dentate nucleus 106. Fastigial nucleus, FNu (medial cerebellar nucleus) Globose nucleus, GNu (posterior interposed cerebellar nucleus) DNu FNu Emboliform nucleus GNu (anterior interposed cerebellar nucleus) Dentate nucleus, DNu (lateral cerebellar nucleus) Inferior medullary velumHilum of dentate nucleus DNu UvulaTela choroidea Nodulus Tonsil of cerebellumChoroid plexus Posterior (dorsal)Anterior (ventral) cochlear nucleuscochlear nucleus Lateral recess of fourth ventricle Spinal trigeminal tract Restiform body Spinal trigeminal nucleus (pars oralis) Inferior (spinal) vestibular nucleus Nucleus prepositus Solitary nuclei and tract Medial vestibular nucleus Medial longitudinal fasciculus Tectospinal tractPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

The Cerebellar Nuclei 113

GNu 5-16 Transverse section through dorsal portions of pons at the 114 Internal Morphology of the Spinal Cord and Brain in Stained Sections ENu level of the abducens nucleus (and facial colliculus) and through rostral portions of the cerebellar nuclei. For additional details of the pons at this level see Figure 5-17 on page 116. Fastigial nucleus, FNu (medial cerebellar nucleus) Globose nucleus, GNu (posterior interposed cerebellar nucleus) Emboliform nucleus, ENu (anterior interposed cerebellar nucleus) Dentate nucleus (lateral cerebellar nucleus) FNuSuperior cerebellar peduncle (brachium conjunctivum)Superior vestibular nucleus Abducens nucleus Juxtarestiform body Inferior Restiform body cerebellar Medial vestibular nucleus peduncle Spinal trigeminal tract Lateral vestibular nucleus Spinal trigeminal nucleus Facial nerve (pars oralis) Facial nerve Facial motor nucleus Central tegmental tract Abducens nerve Medial longitudinal fasciculus Tectospinal tractPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

The Cerebellar Nuclei 115

Posterior longitudinal fasciculus Superior medullary velum 5-17 Transverse section of the caudal 116 Internal Morphology of the Spinal Cord and Brain in Stained Sections Abducens nucleus pons through the facial motor nucleus, abducens Medial longitudinal fasciculus nucleus (and facial colliculus), and the in- Superior Tectospinal tract tramedullary course of fibers of facial and ab- vestibular ducens nerves. nucleus Superior vestibular nucleus Superior Restiform body cerebellar peduncleMedial vestibular nucleus SSNu Facial nerve, Juxtarestiform body internal genu Reticular formationLateral vestibular nucleus Mesencephalic tract Medial and nucleus Solitary nuclei and tract lemniscus Superior salivatory nucleus, SSNu Spinal trigeminal tract Principal sensory nucleusSpinal trigeminal nucleus (pars oralis) Trigeminal motor nucleus Trigeminal nerve Facial nerve Anterior spinocerebellarFacial motor nucleus tract Rubrospinal tract Anterolateral system Lateral lemniscus Central tegmental tract Superior olive Trapezoid body Pontine nuclei and nuclei Abducens nerve Corticospinal fibers Pontocerebellar fibers Ventral trigeminothalamic tract Pontine nuclei Degenerated corticospinal fibers Nucleus raphe, magnusPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Pons With MRI and CT 117

Medial longitudinal fasciculus 5-18 Transverse section of the pons through the rostral pole of the 118 Internal Morphology of the Spinal Cord and Brain in Stained Sections Tectospinal tract facial nucleus and the internal genu of the facial nerve and rostral portions of the abducens nucleus. Superior medullary velum Facial nerve, Internal genu (Fac, G) Superior Mesencephalic nucleus cerebellar and tract peduncle Anterior spinocerebellar tract Posterior longitudinal fasciculus Superior vestibular Fac,G Principal sensory nucleus nucleus (caudal part) Reticular Abducens nucleus formation Trigeminal motor nucleus Mesencephalic nucleus (caudal part) Middle cerebellar peduncle and tractSuperior salivatory nucleus Trigeminal nerve Anterolateral system Spinal trigeminal nucleus Rubrospinal tract and tract (rostral end) Central tegmental tract Facial nerveFacial motor nucleus Medial lemniscusAnterolateral system Pontine nuclei Lateral lemniscus Pontocerebellar fibers Superior olive Abducens nerve Ventral trigeminothalamic tract Degenerated corticospinal fibers Corticospinal fibers Pontine nuclei Trapezoid body Nucleus raphe, magnus Corticospinal fibersPost. column/med. lemniscus sys. (somatomotor) Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Pons With MRI and CT 119

5-19 Transverse section of the pons through the principal sensory 120 Internal Morphology of the Spinal Cord and Brain in Stained Sections nucleus and motor nucleus of the trigeminal nerve. Medial longitudinal fasciculus Superior medullary velum Central grey (periventricular grey) Posterior longitudinal fasciculus Mesencephalic nucleus Tectospinal tract Mesencephalic tractPrincipal sensory nucleus Reticular formation Superior cerebellar peduncle Trigeminal motor nucleus Pontine nuclei (brachium conjunctivum) Trigeminal nerve Anterior spinocerebellar tract Lateral lemniscus (ASCT) Superior olive Nucleus ceruleus Trigeminal motor nucleusLateral lemniscus, nucleus Lateral lemniscus Middle cerebellar peduncle (brachium pontis) ASCT Anterolateral system Rubrospinal tract Central tegmental tract Pontine nuclei Ventral trigeminothalamic tract Pontocerebellar fibersMedial lemniscus Reticulotegmental nucleus Corticospinal fibers Degenerated corticospinal fibers Nucleus raphe, pontis Spinal trigeminal and/or ventralPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system trigeminothalamic fibers (pain/ Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, thermal sense, touch from head) Motor nervediscriminative touch) touch from body) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Pons With MRI and CT 121

5-20 Transverse section of the rostral pons through the exit of the 122 Internal Morphology of the Spinal Cord and Brain in Stained Sections trochlear nerve and rostral portions of the exit of the trigeminal nerve. Cerebral aqueduct Frenulum Central gray (Periaqueductal gray) Nucleus raphe, dorsalis Locus ceruleus Trochlear nerve, exit Mesencephalic nucleus and tract Dorsal trigeminothalamic tract Medial longitudinal fasciculus Reticular formation Superior cerebellar peduncle Lateral lemniscus and (brachium conjunctivum) nuclei of lateral lemniscus Tectospinal tract Central tegmental tract Rubrospinal tract Nucleus centralis, superior Anterolateral system Medial lemniscusVentraltrigeminothalamictractMiddle Cerebellar peduncle Pontine nuclei (brachium pontis)Trigeminal nerve Pontocerebellar Basilar pons fibers Corticospinal fibers Degenerated corticospinal fibersPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Pons With MRI and CT 123

Vascular Syndromes or Lesions of the Pons 5-21 Semidiagrammatic representation of the internal distri- 124 Internal Morphology of the Spinal Cord and Brain in Stained Sections bution of arteries in the pons. Selected main structures are labeledMedial Pontine Syndrome: Results from occlu- Lateral Pontine Syndrome: Results from occlu- on the left side of each section; the general pattern of arterial dis- tribution overlies these structures on the right side. Some patientssion of paramedian branches of basilar artery. sion of long circumferential branches of basilar artery. may have variations of the general distribution patterns of arteries to the pons as shown here. For example, the adjacent territories Deficits Structure Damaged Deficit Structure Damaged served by vessels may overlap to differing degrees at their margins or the territory of a particular vessel may be smaller or larger than• Contralateral hemiplegia • Corticospinal • Ataxia, unsteady gait, • Middle and seen in the general pattern. of arm and leg fibers in basilar fall toward side of lesion superior cerebellar pons peduncles (caudal Abbreviations• Contralateral loss or • Vertigo, nausea, and rostral levels) decrease of position • Medial nystagmus, deafness, BP Basilar pons and vibratory sense lemniscus tinnitus, vomiting • Vestibular and CSp Corticospinal fibers and discriminative (at caudal levels) cochlear nerves CTT Central tegmental tract touch (arm and leg) • Abducens nerve and nuclei MCP Middle cerebellar peduncle fibers or • Ipsilateral paralysis of (brachium pontis)• Ipsilateral lateral rectus nucleus facial muscles • Facial motor ML Medial lemniscus muscle paralysis nucleus (caudal MLF Medial longitudinal fasciculus • Paramedian • Ipsilateral paralysis of levels) Restiform body (ϩjuxtarestiform body ϭ• Paralysis of conjugate gaze pontine reticular masticatory muscles RB inferior cerebellar) toward side of lesion formation • Trigeminal motor Reticular formation (pontine gaze • Ipsilateral Horner nucleus RetF Superior cerebellar peduncle center) syndrome (midpontine levels) SCP (brachium conjunctivum) Comment: The combination of corticospinal deficits • Ipsilateral loss of pain • Descendingon one side of the body coupled with a cranial nerve mo- and thermal sense hypothalamospinaltor deficit on the opposite is called a middle alternating from face fibershemiplegia when the lesion is at this level. Diplopia will re-sult (abducens nerve lesion) on gaze toward the side of the • Contralateral loss of pain • Spinal trigeminallesion. Involvement of the abducens nucleus may also re- and thermal sense tract and nucleussult in an inability to adduct the contralateral medial rec- from bodytus muscle (damage to abducens internuclear neurons). • Anterolateral • Paralysis of conjugate system At caudal levels the lesion may extend lateral to involve horizontal gazethe lateral lemniscus (hypacusis), parts of the middle cere- • Paramedianbellar peduncle (some ataxia), the facial motor nucleus (ip- pontine reticularsilateral facial paralysis), the spinal trigeminal tract and nu- formation (at midcleus (ipsilateral loss of pain and thermal sensation from the to caudal levels)face), and the anterolateral system (contralateral loss of painand thermal sensation from the body). At rostral pontine lev- Comment: The various combinations of theseels the lesion may extend into the medial lemniscus or may deficits may vary depending on whether the lesion is lo-involve only the arm fibers within this structure (cortralat- cated in lateral pontine areas at caudal levels versus lateraleral loss of vibratory sense, proprioception, and discriminative pontine areas at rostral levels. As noted above lesions lo-touch), the motor nucleus of the trigeminal nerve (ipsilat- cated in lateral portions of the pontine tegmentine mayeral paralysis of masticatory muscles), or may damage the an- also extend medial at either caudal or rostral levels andterolateral system and rostral portions of the spinal give rise to some of the deficits discussed above in the sec-trigeminal tract and nucleus (loss of pain and thermal sensa- tion on medial pontine syndrome.tion from the body [contralateral] and from the face [ipsilateral]).

Rostral Mesencephalic nucleus and tract Trochlear nerve Medial longitudinal fasciculus (MLF) Superior medullary velum Lateral lemniscus SCP Fourth ventricle Anterolateral system MLCaudal Trigeminal nuclei: SCP Mesencephalic Motor Principal sensory Vestibular nuclei Trigeminal nerve MCP RetF CSp Arterial Patterns Within The Pons With Vascular Syndrome 125 BP CTTSpinal trigeminal Anterolateral system nucleus Abducens nucleus ML RB MLF MCPSpinal trigeminal tractFacial nerveFacial motor nucleus MLAnterolateral system CSpAbducens nerve Ventral trigeminothalamic fibers Paramedian branches of basilar arteryBasilar pons (BP) Long circumferential branches of basilar artery and branches of anterior inferior cerebellar artery Short circumferential branches of basilar artery Long circumferential branches of basilar artery and branches of superior cerebellar artery

Inferior colliculus, commissure 5-22 Transverse section of the brainstem at the pons–midbrain 126 Internal Morphology of the Spinal Cord and Brain in Stained Sections Inferior colliculus, pericentral nucleus junction through the inferior colliculus, caudal portions of the decussa- tion of the superior cerebellar peduncle, and rostral parts of the basilar pons. Inferior colliculus, central nucleus The plane of section is just caudal to the trochlear nucleus. Posterior longitudinal fasciculus Superior cerebellar Central gray (periaqueductal gray) Lateral lemniscus peduncle, decussation Cerebral aqueduct Inferior colliculus, external nucleus Nucleus raphe, dorsalis Reticular formation Mesencephalic nucleus and tract Trochlear nerve Nucleus ceruleus Dorsal trigeminothalamic tract Medial longitudinal fasciculus Central tegmental tract Anterolateral systemVentral trigeminothalamic tract Tectospinal tract Medial lemniscus Nucleus centralis, superiorRubrospinal tract Parietopontine fibers Occipitopontine fibersCrus cerebri Temporopontine fibers Pontocerebellar fibersCorticospinal fibers Pontine nuclei Degenerated corticospinal fibersPost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Midbrain With MRI and CT 127

Cerebral aqueduct 5-23 Transverse section of the midbrain through the trochlear nu- 128 Internal Morphology of the Spinal Cord and Brain in Stained Sections cleus and decussation of the superior cerebellar peduncle. The section also in- Central gray (periaqueductal gray) cludes caudal parts of the superior colliculus and the rostral tip of the basi- Superior colliculus lar pons. Posterior longitudinal fasciculus Nucleus raphe, dorsalis Inferior colliculus, brachium Trochlear nucleus Mesencephalic nucleus and tract Spinotectal tract Anterolateral Reticular formation Spinothalamic tract system Dorsal trigeminothalamic tract Medial longitudinal fasciculus Tectospinal tract Central tegmental tract Medial lemniscusVentral trigeminothalamic tract Superior cerebellar peduncle, decussation Substantia nigra, pars compacta PPon Parietopontine fibers (PPon) OPon Occipitopontine fibers (OPon) TPon Temporopontine fibers (TPon) Corticospinal fibersCrus cerebri (coCrotirtciocbounlubclarefairbfierbse)rs FPon Degenerated corticospinal fibers Rubrospinal tract Frontopontine fibers (FPon) Pontine nuclei Interpeduncular nucleus Corticospinal fibers Interpeduncular fossa (somatomotor) Post. column/med. lemniscus sys. Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial (proprioception/vibratory sense, (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nerve discriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-gweighted gimage MRI, T2-gweighted gimage CT cistegrnogram The Midbrain With MRI and CT 129

5-24 Transverse section of the midbrain through the superior col- includes rostral portions of the decussation of the superior cerebellar pe- 130 Internal Morphology of the Spinal Cord and Brain in Stained Sections liculus, caudal parts of the oculomotor nucleus, and caudal parts of the red duncle, which, at this level, are intermingled with the caudal part of the nucleus. The plane of section is caudal to the Edinger-Westphal nucleus but red nucleus. Leg ϭ lower extremity; Arm ϭ upper extremity. Cerebral aqueduct Posterior longitudinal fasciculus Central gray (periaqueductal gray) Oculomotor nucleus Superior colliculus Mesencephalic nucleus and tract Dorsal trigeminothalamic tract Spinotectal tract Reticular formation Medial longitudinal fasciculus Spinothalamic tract Inferior colliculus, brachium Ventral trigeminothalamic tract Central tegmental tractMedial geniculate nucleus Posterior (dorsal) Pallidonigral fibers Medial tegmental decussation Nigrostriatal fibers lemniscus Corticonigral fibers Red nucleus SNpc Substantia nigraCrus cerebri pars compacta (SNpc) PPon Leg Substantia nigra OPon Trunk pars reticulata (SNpr) TPon Arm Parietopontine fibers (PPon) SNpr Occipitopontine fibers (OPon) Temporopontine fibers (TPon) Corticospinal (coCrtoirtciocbounlubcalrefiarb feirbs)ers FPon Degenerated corticospinal fibers fibers Superior cerebellar peduncle, decussation Frontopontine fibers (FPon) Rubrospinal tract Anterior (ventral) tegmental decussation Interpeduncular nucleus Oculomotor nerve Post. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial (proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nerve discriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image CT cisternogram The Midbrain With MRI and CT 131

5-25 Transverse section of the midbrain through the superior col- plane of this section is also through caudal portions of the dien- 132 Internal Morphology of the Spinal Cord and Brain in Stained Sections liculus, rostral portions of the oculomotor nucleus, including the Edinger- cephalon including the pulvinar nuclear complex and the medial and lat- Westphal nucleus, and the exiting fibers of the oculomotor nerve. The eral geniculate nuclei. Leg ϭ lower extremity; Arm ϭ upper extremity. Cerebral aqueduct Posterior longitudinal fasciculus Superior colliculus, commissure Superior colliculus Central grey (periaqueductal grey) Spinotectal tract Edinger-Westphal nucleus Mesencephalic tract and nucleus Dorsal trigeminothalamic tract Ventral trigeminothalamic tract Superior colliculus, brachium Pulvinar nuclear complexSpinothalamic tract Brachium, inferior colliculus Lateral Medial geniculate Peripeduncular nucleusgeniculate nucleus nucleus Medial PPon Red nucleus lemniscus OPon TPon SNpc Optic tract Leg SNpr Parietopontine fibers (PPon)Corticonigral fibers Trunk Occipitopontine fibers (OPon)Pallidonigral fibers Arm Temporopontine fibers (TPon)Nigrostriatal fibers Degenerated corticospinal fibersCorticospinal fibers FPon Cerebellorubral fibers and cerebellothalamic fibers Corticonuclear fibers (corticobulbar fibers) Central tegmental tract Substantia nigra, Medial longitudinal fasciculus pars reticulata (SNpr) Frontopontine fibers (FPon) Substantia nigra, Habenulopeduncular tract pars compacta (SNpc) Oculomotor nuclei Oculomotor nerve Post. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial (proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nerve discriminative touch) touch from body) thermal sense, touch from head) nuclei

Anatomical orientation Clinical orientation MRI, T1-weighted image MRI, T2-weighted image MRI, T1-weighted image Anatomical orientation Clinical orientation MRI, T1 weighted image MRI, T2 weighted image MRI, T1 MRI, T2-weighted image MRI, T2- The Midbrain With MRI and CT 133

5-26 Slightly oblique section through the midbrain–diencephalon contains some mammillotegmental fibers. Structures at the midbrain- 134 Internal Morphology of the Spinal Cord and Brain in Stained Sections junction. The section passes through the posterior commissure, the ros- thalamus junction are best seen in an MRI angled to accommodate that tral end of the red nucleus, and ends just dorsal to the mammillary body. specific plane. To make the transition from drawing to stained section At this level, the structure labeled mammillothalamic tract probably also to MRI easy, selected structures in the MRI are labeled. Dorsal trigeminothalamic tract Cerebral aqueduct Pineal Central grey (periaqueductal grey) Pulvinar nuclear complex (Pul) Superior Nucleus of Darkschewitsch colliculus Nucleus of Cajal Medial longitudinal fasciculusCentral tegmental tract Pretectal Posterior Brachium of nuclei commissure Medial superior colliculus Ventral trigemino- geniculate thalamic tract nucleus (MGNu) Spinothalamic tractPeripeduncular nucleus Red nucleus Lateral geniculate Parietopontine fibers (RNu) nucleus (LGNu) Occipitopontine fibers Medial lemniscusTemporopontine fibers Cerebellorubral fibers and Optic Cerebellothalamic fibers tract (OpTr) Transition from crus cerebri (CC) to internal capsule Corticospinal fibers Corticonuclear fibers Subthalamic nucleus (corticobulbar fibers) Supraoptic nucleus Frontopontine fibers Fornix (F) Mammillothalamic tract (MtTr) Habenulopeduncular tract Hypothalamus Third ventriclePost. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial(proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nervediscriminative touch) touch from body) thermal sense, touch from head) nuclei

OpTr OpTr F, MTTr LGNu CC MGNu RNu Pul PulAnatomical orientation Clinical orientation MRI, T2-weighted image MRI, inversion recovery The Midbrain With MRI and CT 135

Vascular Syndromes or Lesions of the Midbrain 136 Internal Morphology of the Spinal Cord and Brain in Stained Sections Medial Midbrain (Weber) Syndrome: May re- position and vibratory sense and of discriminative touch herniation and ipsilateral to the oculomotor deficits is called the Kernohansult from occlusion of paramedian branches of P1 seg- from the contralateral arm and partial loss of pain and phenomenon. As damage from the pressure on the midbrain extends downment of posterior cerebral artery. thermal sensation from the contralateral face. and into the upper pons the pupils are dilated and fixed, eye movement is largely absent, respiration is decreased, and the patient will becomeDeficit Structure Damaged Benedikt syndrome: This results from a larger decerebrate (upper and lower extremities extended, toes pointed in- lesion of the midbrain that essentially involves both of ward, fingers flexed, forearm pronated, head and neck extended).• Contralateral hemiplegia • Corticospinal fibers the separate areas of Weber and Claude. The main deficits are contralateral hemiplegia of arm and leg (cor- 5-27 Semidiagrammatic representation of the internal distributionof arm and leg in crus cerebri ticospinal fibers), ipsilateral paralysis of eye movement of arteries in the midbrain. Selected main structures are labeled on the with dilated pupil (oculomotor nerve), and cerebellar left side of each section; the typical pattern of arterial distribution over-• Ipsilateral paralysis of • Oculomotor nerve tremor and ataxia (red nucleus and cerebellothalamic lies these structures on the right side. The general distribution patterns fibers). Slight variations may be present based on the ex- of the vessels to the midbrain as shown here may vary somewhat fromeye movement: eye tent of the lesion. patient to patient. For example, the adjacent territories served by neighboring vessels may overlap to differing degrees at their marginsoriented down and out Parinaud syndrome: This syndrome is usually or the territory of a particular vessel may be larger or smaller than seen caused by a tumor in the pineal region, such as germi- in the general pattern.and pupil dilated and noma, astrocytoma, pineocytoma/pineoblastoma, or any of a variety of other tumors that impinge on the su-fixed perior colliculi. The potential for occlusion at the cere- bral aqueduct in these cases also indicates that hydro- Comment: This combination of motor deficits at cephalus may be a component of this syndrome. The Abbreviationsthis level of the brainstem is called a superior alternating deficits in these patients consist of a paralysis of upwardhemiplegia. This pattern consists of ipsilateral paralysis of gaze (superior colliculi), hydrocephalus (occlusion of the BP Basilar ponseye movement and contralateral hemiplegia of the upper and cerebral aqueduct), and eventually a failure of eye move- CC Crus cerebrilower extremities. Damage to the corticonuclear (cor- ment due to pressure on the oculomotor and trochlear DecSCP Decussation of the superior cerebellarticobulbar) fibers in the crus cerebri may result in a par- nuclei. These patients may also exhibit nystagmus due to peduncletial deficit in tongue and facial movement on the con- involvement of the medial longitudinal fasciculus. IC Inferior colliculustralateral side. These cranial nerve deficits are seen as a LGNu Lateral geniculate nucleusdeviation of the tongue to the side opposite the lesion on Uncal Herniation: Herniation of the uncus occurs MGNu Medial geniculate nucleusattempted protrusion and a paralysis of the lower half of the in response to large and rapidly expanding lesions in the Medial lemniscusfacial muscles on the contralateral side. Although parts of cerebral hemisphere, this being a supratentorial location. ML Red nucleusthe substantia nigra are frequently involved, akinesia or Uncal herniation is an extrusion of the uncus through the RNu Superior colliculusdyskinesia are not frequently seen. tentorial notch (tentorial incisura) with resultant pressure Superior cerebellar peduncle on the oculomotor nerve and the crus cerebri of the mid- SC Substantia nigraCentral Midbrain Lesion (Claude syndrome) brain. Initially the pupils, unilaterally or bilaterally, may SCP dilate or respond slowly to light, followed by weakness of SN Deficit Structure Damaged oculomotor movement. As herniation progresses the pupils will be fully dilated, eye movements regulated by• Ipsilateral paralysis of • Oculomotor nerve the oculomotor nerve may be slow or absent, and the eyes eye movement: eye will deviate slightly laterally due to the unopposed actions oriented down and out • Red nucleus and of the abducens nerves. There is usually weakness on the and pupil dilated cerebellothalamic contralateral side of the body due to compression of cor- and fixed fibers ticospinal fibers in the crus cerebri. However, if pressure is sufficient the entire midbrain may shift so that there can• Contralateral ataxia be contralateral as well as ipsilateral weakness due to and tremor of pressure on the same side and pressure on the opposite cerebellar origin side of the crus cerebri. This hemiplegia ipsilateral to the Comment: The lesion in this syndrome may ex-tend laterally into the medial lemniscus and the dorsallyadjacent ventral trigeminothalamic fibers. If this was thecase, there could conceivably be a loss or diminution of

Edinger-Westphal nucleus Oculomotor nucleus Anterolateral system Rostral SC Ventral trigeminothalmic MGNu fibers LGNuCaudal Mesencephalic nucleus Oculomotor nerve ML Arterial Patterns Within The Midbrain With Vascular Syndromes 137 Trochlear nucleus IC SN RNu Cerebral aqueduct Periaqueductal gray Medial longitudinal fasciculus ML CC Lateral lemniscus Anterolateral system Anterolateral Ventral trigeminothalamic system fibers DecSCP SN ML SCP CCCC Anteromedial (paramedian) branches of basilar bifurcation and P1 segment BP Anterolateral (short circumferential) branches of theMedial longitudinal fasciculus quadrigeminal and medial posterior choroidal arteriesInterpeduncular fossa Lateral branches of quadrigeminal (level of inferior colliculus), quadrigeminal and posterior medial choroidal arteries (level of superior colliculus) Quadrigeminal and superior cerebellar arteries (level of inferior colliculus), quadrigeminal and posterior medial choroidal arteries (level of superior colliculus) Thalamogeniculate artery

5-28 Coronal section of forebrain through the splenium of the corpus 138 Internal Morphology of the Spinal Cord and Brain in Stained Sections callosum and crus of fornix, and extending into the inferior colliculus and exit of the trochlear nerve. Many of the structures labeled in this figure can be easily identified in the T1-weighted MRI adjacent to the photograph. Cingulate gyrus Cingulum Medial longitudinal stria Lateral longitudinal stria of indusium griseum Atrium of lateral ventricle Hippocampal commissures Tapetum Caudate Corpus callosum, Choroid plexus nucleus, body splenium Caudate nucleus Optic radiations Pulvinar Pineal Stria terminalis Superior cistern Hippocampal Inferior colliculus formation Fornix, crus Caudate nucleus, tail Fimbria of hippocampusLateral ventricle, inferior horn Trochlear nerve Cerebellum Superior cerebellar peduncle

The Diencephalon and Basal Nuclei With MRI 139

5-29 Coronal section of the forebrain through the pulvinar and beled in this figure can be easily identified in the T1-weighted MRI 140 Internal Morphology of the Spinal Cord and Brain in Stained Sections the medial and lateral geniculate nuclei. The section extends into up- adjacent to the photograph. per portions of the midbrain tegmentum. Many of the strucCtiungreuslatlea-gyrus Cingulum Medial longitudinal stria Lateral longitudinal stria of indusium griseum Fornix, body Choroid plexus Lateral ventricle, body External medullary lamina Caudate nucleus, body Insula Stria terminalis (StTer) Medial Corpus callosum, geniculate body nucleus Superior cistern Medial Pulvinar Internal capsule nucleus nuclear Inferior pulvinar complex Retrolenticular limb nucleus Sublenticular limb Lateral Optic radiations nucleus Lateral Hippocampus, geniculate fimbria of nucleus Hippocampal StTer and bed formation nucleus Caudate nucleus, tail Alveus of hippocampusLateral ventricle, inferior horn Superior colliculus, brachium Central grey (periaqueductal grey) Inferior colliculus, brachium Trochlear nucleus Post. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial (proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nerve discriminative touch) touch from body) thermal sense, touch from head) nuclei

The Diencephalon and Basal Nuclei With MRI 141

5-30 Slightly oblique section of the forebrain through the pulvinar, ventral pos- 142 Internal Morphology of the Spinal Cord and Brain in Stained Sections teromedial, and ventral posterolateral nuclei. The section extends rostrally through the subthalamic nucleus and ends in the caudal hypothalamus just dorsal to the mammillary bodies as seen by the position of the (postcommissural) fornix. Habenular commissure Habenulopeduncular tract Habenular nucleus Pulvinar nuclear complex Lateral Centromedian nucleus of thalamus nucleus Medial Pineal nucleusVentral posterolateral Third nucleus of thalamus ventricleVentral posteromedial Dorsomedial nucleus of thalamus nucleus of thalamus Globus pallidus: Lateral segment Internal capsule, Medial segment posterior limbSubthalamic nucleus Zona incerta Column of fornix Ansa lenticularis Lenticular fasciculus Anterior commissure Thalamic fasciculus Mammillothalamic tract Hypothalamus Post. column/med. lemniscus sys. Corticospinal fibers Anterolateral system Spinal trigeminal and/or ventral Sensory Cranial (proprioception/vibratory sense, (somatomotor) (pain/thermal sense, trigeminothalamic fibers (pain/ Motor nerve discriminative touch) touch from body) thermal sense, touch from head) nuclei

The Diencephalon and Basal Nuclei With MRI 143

5-31 Coronal section of the forebrain through the lateral of the structures labeled in this figure can be easily identified 144 Internal Morphology of the Spinal Cord and Brain in Stained Sections dorsal nucleus, massa intermedia, and subthalamic nucleus. Many in the T1-weighted MRI adjacent to the photograph. Medial longitudinal stria Cingulate gyrus of indusium griseum Cingulum Corpus callosum, body Lateral longitudinal stria Fornix, body Lateral ventricle, body Caudate nucleus, body Stria medullaris thalami Lateral dorsal nucleus of thalamus Stria terminalis (StTer) Internal medullary lamina Choroid plexus External medullary lamina andInternal capsule, thalamic reticular nucleus posterior limb InsulaExtreme capsule Putamen Dorsomedial Ventral lateral Claustrum nucleus nucleusExternal capsule StTerGlobus pallidus: Hippocampal formation Red Thalamic fasciculusLateral segment nucleus Zona incertaMedial segment Lenticular fasciculus Optic tract Caudate Subthalamic nucleus nucleus, tail CrusLateral ventricle, cerebri inferior horn Substantia nigra Crus cerebri Basilar pons Alveus of hippocampus Cerebellothalamic fibers Posterior cerebral artery Corticospinal fibers (somatomotor)