A B B R E V I A T I O N S GSA
GSE GVA GVE SSA SVA
General Somatic Afferent General Somatic Efferent General Visceral Afferent General Visceral Efferent Special Somatic Afferent Special Visceral Afferent
SVE SL SA SE VA VE
Special Visceral Efferent Sulcus Limitans Somatic Afferent Somatic Efferent Visceral Afferent Visceral Efferent
Functional Components of the Spinal Cord and Brainstem
97
Thoracic cordLumbosacral cord
Spinal nerves Cranial nerves
1 2
3
4
5 6
7
8
9
10
11
12 13
14 15
16
17
18
19 20
21
22
23
26
24
25 Cervical cord
SL
1. Oculomotor nuc. (GSE/SE)
Midbrain
Midbrain
2. Edinger-Westphal preganglionic nuc. (GVE/VE) 3. Trochlear nuc. (GSE/SE)
4. Mesencephalic nuc. & tr.
of V (GSA/SA)
5. Abducens nuc. (GSE/SE)
Pons
Pons
11. Hypoglossal nuc. (GSE/SE) 12. Dorsal motor nuc. of vagus (GVE/VE) 13. Inf. salivatory nuc. (GVE/VE) 14. Nuc. ambiguus (SVE/SE) 15. Solitary nuc. and tr.
15a: gustatory nuc. (SVA/VA) 15b: cardiorespiratory nuc (GVA/VA) 16. Vestibular nuclei (SSA/SA)
S = Sup; L = Lat; M = Med; Sp. = Spinal 17. Cochlear nuc. (SSA/SA)
18. Spinal trigeminal nuc. (GSA/SA) (pars interpolaris, pars caudalis)
Medulla oblongata
Medulla oblongata
19. Medial motor cell column (GSE/SE) 20. Accessory nuc. (GSE/SE)
21. Lateral motor cell columns (GSE/SE) 22. Intermediolateral cell column (GVE/VE) 23. Visceral afferent (sympathetic) receptive areas (GVA/VA)
24. Substantia gelatinosa, nucleus proprious and associated GSA/SA receptive areas 25. Sacral parasympathetics (GVE/VE) 26. Visceral afferent (parasympathetic) receptive areas (GVA/VA), also called the sacral parasympathetic nuclei
Spinal cord
Spinal cord
6. Sup. salivatory nuc. (GVE/VE) 7. Motor trigeminal nuc. (SVE/SE)
8. Motor facial nuc. (SVE/SE)
9. Principal sensory nuc of V (GSA/SA) 10. Spinal trigeminal nuc. (GSA/SA) (pars oralis)
SL SL
S L
M SP a
b
21
The medial-to-lateral positions of brainstem cranial nerve and spi- nal cord nuclei as shown here are the same as in Figure 6-1. This diagrammatic posterior (dorsal) view shows: 1) the relative positions and names of specific cell groups and their associated functional components;
2) the approximate location of particular nuclei in their specific division of brainstem and/or spinal cord; and 3) the rostrocaudal continuity of cell
6-2
columns (either as continuous or discontinuous cell groups) from one divi-sion of the brainstem to the next or from brainstem to spinal cord. The nucleus ambiguus is a column of cells composed of distinct cell clusters interspersed with more diffusely arranged cells, much like a string of beads. Nuclei associated with CNs I and II are not shown. The color cod- ing used on this figure correlates with that on Figure 6-1 (facing page).
98
6: Internal Morphology of the Spinal Cord and Brain in Stained Sections—The Spinal Cord with CT and MRITransverse section of the spinal cord showing the characteristics of a sacral level. The gray matter occupies most of the cross-section; its H-shaped appear- ance is not especially obvious at sacral–coccygeal levels. The white matter is a compara- tively thin mantle. The sacral cord, although small, appears round in the CT myelogram. Note the appearance of the sacral spinal cord surrounded by the upper portion of the cauda equina(left) and the cauda equina as it appears caudal to the conus medullaris in the lum- bar cistern(right). Compare with Figure 2-4 on p. 10.
6-3A
Medial motor nuclei (lamina IX)Lateral motor nuclei (lamina IX)
Anterolateral system Reticulospinal tract
Dorsolateral tract Posteromarginal nucleus (lamina I) Lateral corticospinal tract Propriospinal fibers (ProSp)Nucleus proprius (laminae III,IV)
Substantia gelatinosa (lamina II)
Gracile fasciculus Intermediate zone (lamina VII) ProSp Post. column/med. lemniscus sys. (proprioception/vibratory sense, discriminative touch)
Corticospinal fibers (somatomotor) Anterolateral system (pain/thermal sense, touch from body) Sensory Motor
Cranial nerve nuclei
The Spinal Cord with CT and MRI
99
Anatomical orientationClinical orientation
Lumbar cistern Anterior horn Cauda equina Posterior horn Filum terminale internum CT myelogramCT myelogram Posterior horn, SA input 6-3A, 6-3B Secondary visceral grey, VA input Sacral parasympathetic nuclei, VE cells
Medial motor cell column,SE cells
Lateral motor cell column, SE cells
6-3B
100
6: Internal Morphology of the Spinal Cord and Brain in Stained SectionsTransverse section of the spinal cord showing its characteristic 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 sur- round the lower levels of the lumbar spinal cord (right), see also Figure 2-4 on p. 10.
6-4A
Medial motor nuclei (lamina IX)Lateral motor nuclei (lamina IX)
Anterolateral system Medullary (lateral) reticulospinal fibers
Dorsolateral tract Anterior root fibers Medial longitudinal fasciculusLateral corticospinal tract Propriospinal fibers (ProSp)
Nucleus proprius (laminae III,IV)
Substantia gelatinosa (lamina II)
Gracile fasciculus Anterior corticospinal tract
Intermediate zone (lamina VII)
Area of lamina VI
Area of lamina V Area of lamina VIII
Posteromarginal nucleus (lamina I)
Medial division fibers ProSp
Lateral vestibulospinal tract and pontoreticulospinal (Medial reticulospinal) tract
Rubrospinal tract Anterior median fissure
Posterior median sulcus Post. column/med. lemniscus sys. (proprioception/vibratory sense, discriminative touch)
Corticospinal fibers (somatomotor) Anterolateral system (pain/thermal sense, touch from body)
ProSp
Sensory Motor Cranial nerve nuclei
The Spinal Cord with CT and MRI
101
Anterior root Anterior horn Posterior root Posterior horn CT myelogramCT myelogramAnatomical orientationClinical orientation Posterior horn, SA input 6-4A, 6-4B
Medial motor cell column,SE cells Lateral motor cell column, SE cells
6-4B
102
6: Internal Morphology of the Spinal Cord and Brain in Stained SectionsTransverse section of the spinal cord showing its characteristic 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 levels and to lumbar levels. The overall shape of the cord is round. The thoracic spinal cord appears round in CT myelogram.
6-5A
Post. column/med. lemniscus sys. (proprioception/vibratory sense, discriminative touch)Corticospinal fibers (somatomotor) Anterolateral system (pain/thermal sense, touch from body)
Medial motor nuclei (lamina IX)
Rubrospinal tract Medullary (lateral) reticulospinal tract
Posterior intermediate sulcus Medial longitudinal fasciculus
Medial division fibers of posterior root Propriospinal fibers (ProSp)
Gracile fasciculus Cuneate fasciculus Anterior corticospinal tract
Intermediolateral cell column (lamina VII) Lateral vestibulospinal tract
Spino-olivary fibers
Dorsolateral tract
ProSp Dorsal thoracic nucleus of Clarke (lamina VII)
Nucleus proprius (laminae III,IV)
Posteromarginal nucleus and substantia gelatinosa (laminae I,II) ProSp Anterior white commissure
Posterior spinocerebellar tract Anterior spinocerebellar tract Anterior root fibers Anterolateral system
Lateral corticospinal tract Anterior median fissure
Posterior median sulcus Posterolateral sulcus Pontoreticulospinal tract
Sensory Motor Cranial nerve nuclei
The Spinal Cord with CT and MRI
103
Anatomical orientationClinical orientation
Anterior horn Anterior root Lateral horn Posterior root Posterior horn CT myelogramCT myelogram Posterior horn, SA input6-5A, 6-5BSecondary visceral grey, VA input Sacral parasympathetic nuclei, VE cells
Medial motor cell column,SE cells
6-5B
104
6: Internal Morphology of the Spinal Cord and Brain in Stained SectionsMedial motor nuclei (lamina IX)
Rubrospinal tract Medullary (lateral) reticulospinal tract
Posterior intermediate sulcus Medial longitudinal fasciculus and tectospinal tract
Propriospinal fibers (ProSp)
Gracile fasciculus (FGr) Posterolateral sulcus
Cuneate fasciculus (FCu) Area of lamina VI Intermediate zone (lamina VII)
Area of lamina V Area of lamina VIII
Lateral motor nuclei (lamina IX)
Substantia gelatinosa (lamina II)
Posteromarginal nucleus (lamina I)
Dorsolateral tract
Interfascicular fasciculus Reticular nucleus of cervical cord
Nucleus proprius (laminae III, IV) ProSp Anterior white commissure Anterior corticospinal tract
Posterior spinocerebellar tract Anterolateral system Spino-olivary fibers Anterolateral sulcus Lateral vestibulospinal tract Pontoreticulospinal (medial reticulospinal) tract
Lateral corticospinal tract Anterior median fissure
Posterior median sulcus Anterior spinocerebellar tract Post. column/med. lemniscus sys. (proprioception/vibratory sense, discriminative touch)
Corticospinal fibers (somatomotor) Anterolateral system (pain/thermal sense, touch from body)
Area X
Sensory Motor Cranial nerve nuclei
Transverse section of the spinal cord showing its characteristic 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 (beginning at about C4 and extending through C8) appear oval in MRI (left) and in CT myelogram (center and right). Although frequently called lamina X, Rexed (1954) clearly describes nine laminae (I–IX) and an “area X, the central gray substance.” This original designation is used here.
6-6A
The Spinal Cord with CT and MRI
105
Anatomical orientationClinical orientation Posterior horn, SA input
6-6A, 6-6B
Medial motor cell column, SE cells Lateral motor cell column, SE cells
Anterior horn Anterior root Posterior root Posterior horn FGr + FCu CT myelogramCT myelogramMRI, T2-weighted image
6-6B
106
6: Internal Morphology of the Spinal Cord and Brain in Stained SectionsTransverse section of the spinal cord at the C1 level. Lateral corticospinal fibers are now located medially toward the decussation of the corticospinal fibers, also called the motor decussation or pyramidal decussation (see also Figure 6-10, p. 112). At this level, fibers of the spinal trigeminal tract are interdigitated with those of the dorso- lateral tract. The spinal cord at C1 and C2 levels appears round in CT myelogram when compared to low cervical levels (see Figure 6-6).
6-7A
Medial motor nucleiRubrospinal tract Medullary (lateral) reticulospinal tract
Posterior intermediate sulcus Medial longitudinal fasciculus
Propriospinal fibers (ProSp)
Gracile fasciculus (FGr) Cuneate fasciculus (FCu) Anterior spinocerebellar tract
Magnocellular portion of spinal trigeminal nucleus Spino-olivary fibers
Accessory nucleus
Gelatinosa portion of spinal trigeminal nucleus Spinal trigeminal tract and dorsolateral tract junction
ProSp ProSp Anterior corticospinal tract Pyramidal decussation (PyDec)
Posterior spinocerebellar tract Anterolateral system Lateral vestibulospinal tract
Pontoreticulospinal (Medial reticulospinal) tract Tectospinal tract
Posterior median sulcus Posterior column/medial lemniscus system (proprioception/vibratory sense, discriminative touch)
Corticospinal fibers (somatomotor) Anterolateral system (pain/thermal sense, touch from body) Spinal trigeminal and/or ventral trigeminothalamic fibers (pain/ thermal sense, touch from head)
Lateral corticospinal tract (LCSp)
Sensory Motor Cranial nerve nuclei
The Spinal Cord with CT and MRI
107
6-7B
Anatomical orientationClinical orientation
PyDec C1anteriorhorn LCSpfibers C1posteriorhorn FGr+FCu CT myelogramCT myelogram Junction of posterior horn with the gelatinosa and magnocellular parts of the spinal trigeminal nucleus
6-7A, 6-7B Medial motor cell column, SE cells
Accessory nucleus, SE cells
108
6: Internal Morphology of the Spinal Cord and Brain in Stained Sections—Arterial Patterns within the Spinal CordV ascular Syndromes or Lesions of the Spinal Cord Acute Central Cervical Spinal Cor d Syndr ome
This results from occlusion of the anterior spinal artery. DeficitStructure Damage UÊBilateral paresis or flaccid paralysis of upper extremitiesUÊi`>Ê«ÀÌÃÊvÊLÌ Ê>ÌiÀ>ÊVÀÌVë>Ê tracts; ventral gray horns at cervical levels UÊIrregular loss of pain and temperature sen- sations bilaterally over body below lesionUÊÌiÀ>ÌiÀ>ÊÃÞÃÌiÊwLiÀÃÊ«>ÀÌ>ÊÛÛi- ment bilaterally) Hyperextension of the neck may cause damage to the vertebral arteries (origin of the anterior spinal artery), or it may directly damage the anterior spinal artery, causing a spasm. This vascu- lar damage leads to a temporary or permanent interruption of blood supply. Deficits may resolve within a few hours or may be permanent, depending on the extent of vascular complication. Sparing of the posterior columns (proprioception, vibratory sense) is a hallmark; approximately the anterior two-thirds of the spinal cord is ischemic.Thr ombosis of Anterior Spinal Artery
This may occur in a hypotensive crisis, as a result of trauma resulting from a dissecting aortic aneurysm, or in patients with atherosclerosis. It may occur at all spinal levels, but is more fre- quently seen in thoracic and lumbosacral levels unless trauma is the primary cause. Results are bilateral flaccid paraplegia (if the lesion is below cervical levels) or quadriplegia (if the lesion is in cervical levels), urinary retention, and loss of pain and temperature sensation. Flaccid muscles may become spastic over a period of a day to weeks, with hyperactive muscle stretch reflexes and extensor plantar (Babinski) reflexes. In addition, lesions at high cervical levels may also result in paralysis of respiratory muscles. The artery of Adamkiewicz (a large spinal medullary artery) is usually located at spinal levels T12–L1 and more frequently arises on the left side. Occlusion of this vessel may infarct lumbosacral levels of the spinal cord.Hemorrhage in the Spinal Cor d
This is rarely seen, but may result from trauma or bleeding from congenital vascular lesions. Symptoms may develop rapidly or gradually in stepwise fashion, and blood is usually present in the cerebrospinal fluid.Arteriovenous Malformation in the Spinal Cor d
More frequently found in lower cord levels. Symptoms of a spinal AVM (micturition prob- lems are seen early, motor deficits, lower back pain) may appear over time and may seem to resolve then recur (get better, then worse). These lesions are usually found external to the cord (extramedullary) and can be surgically treated, especially when the major feeding vessels are few in number and easily identified. Foix-Alajouanine syndrome is an inflammation of spinal veins, with subsequent occlusion that results in infarct of the spinal cord and a necrotic myelitis. The symptoms are ascending pain and a flaccid paralysis.Semi-diagrammatic representation of the internal blood supply to the spinal cord. This is a tracing of a C4 level, with the positions of principal tracts shown on the left, the general pattern of blood vessels on the right, and the color-coded pathways correlate with those on Figure 6-7.
6-8
ABBREVIATIONS AH AWCom CenC IZ LE Anterior (ventral) horn Anterior white commissure Central canal Intermediate zone Representation of lower extremityN PH S T UE
Representation of neck fibers Posterior (dorsal) horn Representation of sacral fibers Representation of truck fibers Representation of upper extremity
Br own-Séquar d Syndr ome
This syndrome is a hemisection (functional hemisection) of the spinal cord that may result from trauma, compression of the spinal cord by tumors or hematomas, or significant protrusion of an intervertebral disc. The deficits depend on the level of the causative lesion. The classic signs are: 1) a loss of pain and thermal sensation on the contralateral side of the body beginning about one to two segments below the level of the lesion (damage to anterolateral system fibers); 2) a loss of discrimi- native touch and proprioception on the ipsilateral side of the body below the lesion (interruption of posterior column fibers); and 3) a paralysis on the ipsilateral side of the body below the lesion (dam- age to lateral corticospinal fibers). This syndrome is classified as an incomplete spinal cord injury, and patients with this lesion may regain some degree of motor and sensory function. Compression of the spinal cord may result in some, but not all, of the signs and symptoms of the syndrome.Syringomyelia
Syringomyelia is a cavitation within the central region of the spinal cord. A cavitation of the central canal with an ependymal cell lining is hydromyelia. A syrinx may originate in central portions of the spinal cord, may communicate with the central canal, and is most commonly seen in cervical levels of the spinal cord. The most common deficits are a bilateral loss of pain and thermal sensation due to damage to the anterior white commissure: the loss reflects the lev- els of the spinal cord damaged (e.g., a cape distribution over the shoulder and upper extremities). The other commonly seen deficit results from extension of the cavity into the anterior horn(s). The result is unilateral or bilateral paralysis of the upper extremities (cervical levels) or lower extremities (lumbosacral levels) due to damage to spinal motor neurons. This paralysis is char- acteristically a lower motor neuron deficit. A syrinx in the spinal cord, particularly in cervical levels, may be associated with a variety of other developmental defects in the nervous system.Spinal Cord Lesions General Concepts
A complete spinal cord lesion is characterized by a bilateral and complete loss of motor and sensory function below the level of the lesion persisting for more than 24 hours. The vast major- ity of the patients with complete lesions (95%+) will suffer some permanent deficits. Incomplete spinal cord lesions are those with preservation of sacral cord function at presentation. The above described cases are examples of incomplete spinal cord lesions.Arterial Patterns within the Spinal Cord with Vascular Syndromes
109
High Cervical
The phrenic nucleus is located in central areas of the anterior horn at levels C3–C7 and receives descending input from nuclei of the medulla (mainly in the reticular formation) that influence respiration, particularly inspiration. The phrenic nerve originates primarily from level C4 with some contributions from C3 and C5 and innervates the diaphragm. A complete spinal cord lesion between C1 and C3 interrupts medullary input to the phrenic nucleus and may result in immediate respiratory (and potentially cardiac) arrest. This constitutes a medical emergency necessitating intervention within minutes, or the patient will die. Anterolateral systemPosterior spinal artery Anterior spinal artery
Posterior radicular artery to posterior root Posterior spinocerebellar tract Anterior spinocerebellar tractRubrospinal tract
Lateral corticospinal tract PH IZ NUET
LE
UE
TLE S AH
CenCAWCom
Posterior spinal medullary artery Dorsolateral tract
Fasciculus cuneatus
Fasciculus gracilis Propriospinal fibers Reticulospinal and vestibulospinal tracts Medial longitudinal fasciculus and anterior corticospinal tract
Arterial vasocorona (AVC) Anterior radicular artery to anterior root Anterior spinal medullary artery
Segmental artery Sulcal artery
AVC
6-8
110
6: Internal Morphology of the Spinal Cord and Brain in Stained Sections—The Degenerated Corticospinal TractAll of the brainstem sections used in Figures 6-11 through 6-15 (medulla), 6-19 through 6-22 (pons), and 6-24 through 6-29 (midbrain, except 6-25) are from an individual who had an infarct (green in drawing) in the posterior limb of the internal capsule. This lesion damaged corticospinal fibers (gray in drawing), resulting in a contralateral hemiplegia of the arm and leg, and damaged sensory radiations that travel from thalamic nuclei to the somatosensory cortex through the posterior limb of the internal capsule. Although the patient survived the initial episode, corticospinal fibers (gray) distal to the lesion (green) underwent degenerative changes and largely disappeared. This Wallerian (anterograde) degeneration takes place because the capsular infarct effectively separates the descending corticospinal fibers from their cell bodies in the cerebral cortex. Consequently, the location of corticospinal 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 characterized by the obvious lack of myelinated axons in these structures when compared to the opposite side. In the brainstem, these degenerated fibers are ipsilateral to their cells of origin, but are contralat- eral to their destination in the spinal cord—hence, the contralateral motor deficit when these fibers are damaged rostral to the motor decussation. These images give the user the unique opportunity of seeing where corticospinal fibers are located at all levels of the human brainstem. Also, one is constantly reminded of: 1) the relationship of corticospinal fibers to other structures; 2) the deficits one can expect to see at representative levels due to this lesion; and 3) the general appearance of degenerated fibers in the human central nerv- ous system. These images can be adapted to a wide range of instructional formats.