Spinal Cord Anatomy, Localization, and Overview of Spinal Cord Syndromes

Home , Conus medullaris, Rexed laminae

KEY POINT: Ⅲ A notch in the SPINAL CORD ANATOMY, inferior aspect of the pedicle will LOCALIZATION, AND contribute to the boundary of the intervertebral OVERVIEW OF SPINAL foramen when adjacent CORD SYNDROMES vertebrae are articulated and Gregory Gruener, Jose´ Biller through which the spinal nerve and intervertebral ABSTRACT vessels will pass. Spinal cord syndromes are “unique” clinical presentations that localize lesions to the spinal cord by their pattern of anatomic dysfunction while implying their underlying etiology. Recognizing these patterns and their significance is best accomplished by relearning and appreciating the relevant anatomy and relationships, which are the major focus of this review. This clinical-anatomic background will provide the frame- work for the clinical topics that follow in this issue.

ANATOMY OF THE SPINAL A notch in the inferior aspect of the CORD pedicle will contribute to the boundary of the intervertebral foramen when ad- Relationship to the Vertebral jacent vertebrae are articulated and Levels and Spine through which the spinal nerve and in- The typical vertebra consists of a co- tervertebral vessels will pass. lumnar body with a larger transverse An intervertebral disc is interposed than anterior-posterior diameter and between each vertebral body and con- serving as the primary support for the sists of alternating, crisscrossing bands spine. The vertebral arch extends from of fibrous connective tissue, the annu- the body, forming a protective enclo- lus fibrosus, which surround a gelati- sure, and consists of a pedicle on ei- nouslike core, nucleus pulposus. The ther side that unites posteriorly vertebral discs will contribute 25% of the through the two laminae. Three pro- height of the vertebral column. Several 11 cesses arise from the vertebral arch, ligaments and fibrous attachments of laterally the transverse and posteriorly muscles help to bind together and en- the spinous, serving as the attachment close the vertebral column. The most site for muscles (Figure 1-1). Four prominent are the anterior longitudinal separate articular processes, a superior (along the anterior aspect of the bodies), pair extending cranially and an infe- the posterior longitudinal (along their rior pair extending caudally, serve to posterior aspect), the ligamentum fla- direct or limit movement to specific vum (posterior wall of spinal canal), and directions by articulating with the ver- the interspinous ligament. tebra above and below (Figure 1-2). The fused periosteum of the cra-

Relationship Disclosure: Dr Gruener has received personal compensation for speaking engagements with Medical Education Resources, Inc. Dr Biller has nothing to disclose. Unlabeled Use of Products/Investigational Use Disclosure: Drs Gruener and Biller have nothing to disclose.

FIGURE 1-1 Functions of the constituent parts of a vertebra. Reprinted with permission from Grant JCB. An atlas of anatomy. 6th ed. Baltimore: Williams & Wilkins, 1972.

nium and meningeal layer of the dura space, epidural space, which extends matter will separate caudal to the fo- the length of the spinal column (Fig- ramen magnum, forming an anatomic ure 1-3). Within this space reside fatty

FIGURE 1-2 Lateral view of a lumbar (second) vertebra. Sup ϭ superior; Inf ϭ inferior. Modified with permission from Grant JCB. An atlas of anatomy. 6th ed. Baltimore: Williams & Wilkins, 1972.

Continuum: Lifelong Learning Neurol 2008;14(3) KEY POINT: tissue and the vertebral venous plexus. tively numbered vertebrae (C2 Ⅲ At birth the The separation of these fused layers of through C7), but C8 above the T1 ver- spinal cord connective tissue allows the vertebral tebrae. The remaining spinal nerves typically extends column to move separately relative to will exit below the vertebrae of the to the lower the dural sac that surrounds the spinal corresponding number. The spinal border of L3. By cord and roots. The dorsal and ventral nerves will have a dorsal root ganglion adulthood its tip roots will enter a dural sleeve at the usually located within the interverte- is usually at the level of their intervertebral foramina, bral foramen. C1 lacks a cutaneous L1-2 vertebral lateral to the dorsal spinal ganglia, fus- sensory dermatome. Below the L1 ver- disk level but ing to form the spinal nerves. A layer tebra, lumbar and sacral spinal nerve can end at T12 of pia mater surrounds the surface of roots need to descend in order to or descend to the spinal cord, and between it and the reach their point of exit; this collection the lower border of the L2 inner layer of the arachnoid tissue is of spinal roots is called the cauda vertebrae. the subarachnoid space. Between suc- equina. The cord will terminate in a cessive nerve roots, a bandlike exten- thin-walled sac covered by pia mater, sion of the pia mater will arise from the filum terminale, which fuses with the surface of the spinal cord, dentic- the periosteum of the dorsal surface of ulate ligament, attaching to the dura the coccyx. and serving to anchor the spinal cord The gray matter of the spinal cord (Figure 1-4). The ventral nerve roots can be divided into a posterior column lie anterior and the dorsal nerve roots posterior to this ligament. The spinal cord is cylindrical in shape, but flattened dorsoventrally. It is widest at the cervical enlargement, and a second enlargement occurs in the lumbosacral level of the cord, both reflecting the innervation levels of the limbs. At birth the spinal cord typically extends to the lower border of L3. By adulthood its tip is usually at the L1-2 vertebral disk level but can end at T12 or descend to the lower border of the L2 vertebrae. Each segment of the spinal cord usually has a set of dorsal (sensory) 13 and ventral (motor) rootlets that emerge and join together to form their corresponding root; dorsal roots have their corresponding ganglia (dorsal root ganglia). The dorsal and ventral roots will fuse to form the spinal nerve as it exits from the spinal canal. The spinal nerves then divide into individual branches. There are usually 31 pairs of spinal nerves: eight cervical, 12 thoracic, five lumbar, five sacral, and usually one coccygeal (Figure FIGURE 1-3 Spaces associated with the spinal meninges. 1-5). The first pair of spinal nerves will Modified with permission from Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. exit between the skull and the atlas London: Saunders, 2007:49. Copyright © 2007, Elsevier. (C1), the next six above their respec-

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KEY POINT: Ⅲ The first pair of spinal nerve roots will exit between the skull and the atlas (C1), the next six above their respectively numbered vertebrae (C2 through C7), but C8 above the T1 vertebrae. The remaining spinal nerves will exit Relationships of the sixth cervical spinal nerve. below the FIGURE 1-4 vertebrae of the Reprinted with permission from Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. London: Saunders, 2007:171. Copyright © 2007, Elsevier. corresponding number.

(or horn), a lateral column, and an laminae I through V, more clearly anterior column (or horn) that respec- demonstrate a laminated appearance. tively “divide” the adjacent white matter into a posterior, lateral, and ante- Major Ascending Tracts rior funiculus. At the junction The diagrammatic representation of between white and gray matter are both ascending and descending tracts short ascending and descending axons within the spinal cord reflects a level that arise from small neurons within of certainty that, while useful for com- the spinal cord gray matter and com- prehension, oversimplifies a more prise the intrinsic or intersegmental re- complex anatomic distribution and an- flex pathways, proprius bundles (or atomic variations that likely exist system)orfasciculi proprii and are (Nathan et al, 1990; Nathan et al, 1996; named by their location. While the Nathan et al, 2001). Indeed, the con- posterior funiculi primarily consist of cept of a tract as a homogenous group ascending sensory fibers, they also of fibers is also an oversimplification. 14 contain their descending collateral fi- Despite their shortcomings, however, bers, which serve to further integrate such generalizations have proven to intrinsic spinal reflexes and form their be clinically useful. own distinct, but small, fasciculi. The sensory pathways and tracts Within the gray matter of the spi- we will first review are responsible for nal cord cell groups can be identified transmitting sensory information that (right portion of Figure 1-6), with is perceived (conscious) as well as those in the posterior horn participat- nonconscious sensation. The dorsal ing in sensory pathways and those in root ganglia contribute nerve fibers the intermediate and anterior horns that at the dorsal root entry zone will serving motor functions. In addition, further segregate into a medial group layers of synaptic inputs within the of large-diameter fibers, which will en- spinal cord have also been identified. ter the posterior funiculi of the spinal These are called Rexed laminae and cord, and a lateral group of small-di- are labeled I to X (left side of Figure ameter myelinated and unmyelinated 1-6). Those within the posterior horn, fibers. This segregation is modality

Continuum: Lifelong Learning Neurol 2008;14(3) specific and will give rise to the major ascending tracts within the spinal cord (Figure 1-7). This lateral group of fibers will divide into short ascending and descending branches within the tract of Lissauer and predominantly synapse on neurons within laminae I and II of the posterior horn. The posterior column–medial lemniscal pathway receives its input from the largest group of sensory receptors (neuromuscular spindles and Golgi tendon organs) entering through the medial portion of the dorsal root entry zone. These fibers form a lamination within the posterior column, and most medial are those originating from the lower extremity and trunk, fasciculus gracilis, carrying sensory information from the lower extremity; and laterally is the fasciculus cuneatus, carrying similar sensory information from the upper trunk and limb (Figure 1-8). As these fibers enter the posterior column they bifurcate and one branch ascends to the medulla where it will synapse onto its second-order neuron within the nucleus gracilis or cuneatus. Those neurons will then project across the midline in the sensory decussation, continuing their ascent to the thalamus FIGURE 1-5 Vertebral column, spinal cord, and nerve relationships. as the medial lemniscus. The third- Modified with permission from Moore KL, Dalley AF. order neurons of this pathway will Clinically oriented anatomy. Philadelphia: Lippincott then arise from the thalamus and William & Wilkins, 1999:478. project to the somatic sensory cortex. The other branch of that initial bifur- 15 cation of entering fibers will synapse pathway is the anterolateral spinotha- within the posterior gray horn laminae lamic tract (Figure 1-9). This tract II, III, and IV at various levels (the arises from neurons in laminae I, II, IV, ascending branch also gives off collat- and V that receive excitatory as well as erals to the dorsal gray horn). The tra- inhibitory input from neurons within ditional functions of this system are the substantia gelatinosa (lamina II). believed to be relaying conscious pro- The axons that arise from those neu- prioception as well as discriminative rons cross in the anterior commissure touch. Yet, its role in supporting the of the spinal cord and arrange them- motor cortex as it carries out its intri- selves in the anterolateral location cate and precise digital movements within those spinal cord funiculi. may better or more accurately charac- There are two divisions, and the most terize its function and importance anterior is the anterior spinothalamic (Davidoff, 1989). tract, which has a somatotopic organi- The other major conscious sensory zation and mediates the sensory mo-

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modality arranged with cervical representation most medial and sacral most lateral; pain, tickle, and itch sensory modalities are more peripheral while temperature is more medially represented within this tract. These tracts ascend, merge within the brainstem as the spinal lemniscus, are joined later by the trigeminal lemniscus (afferents from the head), and together terminate within the thalamus. Their third-order neurons will also project to the somatic sensory cortex. The spinoreticular tract arises from neurons within laminae V to VII and accompanies the spinothalamic pathway, both as a crossed and uncrossed tract, terminat- FIGURE 1-6 Spinal cord laminae and cell groups ing within the brainstem. It serves as (midthoracic level). an arousal system for the cerebral cor- Reprinted with permission from Fitzgerald MJ, Gruener tex (through the reticular activating G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. London: Saunders, 2007:182. Copyright © 2007, system), and it helps to interpret the Elsevier. nature of a stimulus (pleasurable or not). The spinocerebellar tracts provide dality of touch and pressure. The lat- nonconscious proprioception (Figure eral spinothalamic tract is lateral and 1-8). Fasciculus gracilis collaterals pro- posterior, somatotopically as well as vide information from lower limb primary afferents (especially muscle spin- dle), synapse upon the posterior thoracic nucleus in lamina VII (extends from T1 through L1 spinal cord levels, previously called the dorsal nucleus or Clarke column), and give rise to the posterior spinocerebellar tract. The tract ascends and reaches the cer- 16 ebellum through the inferior cerebellar peduncle. A similar group of afferents from the fasciculus cuneatus provides information from the upper limb and synapses on the accessory cuneate nucleus, which gives rise to the cuneocerebellar tract. It also reaches the cerebellum through the inferior cerebellar peduncle. The following two spinocerebellar tracts will provide information about the state of FIGURE 1-7 Primary afferent neuron targets in the posterior horn. internuncial function in regard to spi-

Reprinted with permission from Fitzgerald MJ, Gruener nal cord reflexes and arise from the G, Mtui E. Clinical neuroanatomy and neuroscience. 5th intermediate gray matter of the spinal ed. London: Saunders, 2007:183. Copyright © 2007, Elsevier. cord. (1) The anterior spinocerebellar tract arises from the lower spinal cord

Continuum: Lifelong Learning Neurol 2008;14(3) and will initially cross, ascend to the superior cerebellar peduncle, cross again to its side of origin, and terminate within the cerebellum. (2) From the upper half of the spinal cord the rostral spinocerebellar tract will ascend and, through the inferior cerebellar peduncle, enter the cerebellum. The remaining tracts to be considered include the spinotectal tract, which ends in the superior colliculus, runs with the spinothalamic tract, and brings somatic sensory information to the superior colliculus. The spinoolivary tract projects to the inferior oli- vary nucleus and through its effects on the contralateral cerebellar cortex will modify motor activity.

Major Descending Tracts The motor cell types within the anterior gray horns are of two types: (1) Alpha motor neurons (physiologically defined as tonic or phasic in regard to the physiologic/functional type of FIGURE 1-8 Ascending pathways (upper cervical level). muscle fibers they innervate) supply GF ϭ gracile fasciculus; CFϭ cuneate the extrafusal skeletal muscle fibers, fasciculus; PLT ϭ posterolateral tract; and (2) gamma motor neurons supply PSCT ϭ posterior spinocerebellar tract; RSCT ϭ rostral spinocerebellar tract; LSTT ϭ lateral spinothalamic tract; the intrafusal muscle fibers of neuro- ASCT ϭ anterior spinothalamic tract; SOT ϭ spinoolivary muscular spindles. The motor unit tract; ASTT ϭ anterior spinothalamic tract; ST ϭ comprises an individual alpha motor spinotectal tract; SRT ϭ spinoreticular tract. neuron, its axon, and all the muscle Reprinted with permission from Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. London: Saunders, 2007:187. fibers (varying from a few to hun- Copyright © 2007, Elsevier. dreds, dependent on the precision of the movement) it will subsequently innervate. Recurrent axons of alpha mo- those effects are abolished by a cord 17 tor neurons excite inhibitory internun- lesion, the disproportionately strong cial neurons, Renshaw cells, which influence of the spinal intrinsic circuits serve to inhibit their own firing (recur- will lead to the clinical phenomenon rent inhibition). At each segmental of spasticity. level of the spinal cord, however, al- Figure 1-10 demonstrates the co- pha motor neurons also receive nu- lumnar organization of motor neurons merous inhibitory (usually on their into groups that then innervate mus- soma) as well as excitatory (through cles with similar function. Those most synapses on their dendritic trees) in- medial innervate the axial muscula- puts. These inputs arrive from both ture, and moving traversely through supraspinal pathways as well as those groups of neurons, they also through the propriospinal neurons (lo- move from the innervation of proximal cal) and their pathways. Most of these to distal limb muscles and finally to the fibers and inputs will exert an inhibi- intrinsic muscles of the hand or foot. tory effect on alpha motor neurons. If Another result of this neuronal organi-

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KEY POINTS: Ⅲ The dorsal root ganglia contribute nerve fibers that will further segregate at the dorsal root entry zone into a medial group of large-diameter fibers that will enter the posterior funiculi of the spinal cord and a lateral group of small-diameter myelinated and unmyelinated fibers.

Ⅲ The traditional functions of the posterior FIGURE 1-9 Spinothalamic pathways (sensory modalities, upper cervical level). column–medial Reprinted with permission from Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and lemniscal system neuroscience. 5th ed. London: Saunders, 2007:187. Copyright © 2007, Elsevier. are believed to relay conscious proprioception zation is alpha neurons innervating ex- The majority of fibers that give rise and to mediate tensor muscles lying ventral or anterior to the corticospinal tract have their or- discriminative to those that innervate flexor muscles. igin in primary motor cortex (perhaps touch. Yet, its Dysfunction of these neurons results in 50%), but supplementary motor cortex role in the clinical features of weakness, atro- and premotor cortex, as well as so- supporting the phy, and fasciculations, as well as matic sensory cortex, also contribute. motor cortex as it carries out its areflexia when their loss is marked. Some of these projections will end on intricate and The long descending tracts (corti- brainstem nuclei (corticobulbar or precise digital cospinal, reticulospinal, tectospinal, corticonuclear), while those from sen- 18 movements may vestibulospinal, raphespinal) and sory cortex project onto sensory nuclei better or more aminergic and autonomic pathways in the brainstem and spinal cord that accurately will terminate on interneurons, which modulate their transmission of sensory characterize its influence alpha and gamma motor information. Those fibers that reach function and neuron function. The rubrospinal tract the medulla form the pyramids, visible importance. is small and lies anterior to the lateral on its ventral surface. Seventy percent corticospinal; in humans its role is un- to 90% of these fibers cross the ventral clear. Similar to sensory pathways, the midline in the pyramidal decussation, discrete locations indicated within the giving rise to the lateral corticospinal accompanying diagrams are used as tract within the spinal cord. A soma- simplifications and conceal a more totopic organization results with fibers complex and variable distribution of destined for the sacral area most lateral these pathways that explains the dis- and those to the cervical, medial (Fig- crepancy at times encountered be- ure 1-11). The remaining fibers de- tween clinical findings and visualized scend uncrossed either within the lat- anatomic lesions. eral corticospinal tract (uncrossed

Continuum: Lifelong Learning Neurol 2008;14(3) KEY POINT: lateral corticospinal tract) or the ma- The reticulospinal tracts, through Ⅲ The lateral jority adjacent to the anterior median shared internuncials with the cortico- spinothalamic fissure as the anterior corticospinal spinal tract, act upon motor neurons of tract is tract to innervate paraspinal and axial axial as well as proximal limb muscles. somatotopically, muscles. At the appropriate level fi- They are considered part of the extra- as well as bers will cross through the anterior pyramidal system of motor control modality, white commissure to provide their (with the lateral vestibulospinal and arranged with contralateral innervation. tectospinal tracts) and are involved in cervical All corticospinal neurons appear ex- locomotion as well as posture. The representation citatory with glutamate as their neuro- medullary reticulospinal tract is be- most anterior transmitter. The corticospinal tract inner- lieved to act on flexor motor neurons and sacral most vates not only alpha and gamma motor and the pontine reticulospinal tract on posterior. Pain, tickle, and itch neurons, but also Renshaw cells, excita- extensor motor neurons. sensory tory and inhibitory internuncials, and, The tectospinal tract arises from modalities are through presynaptic inhibition, sup- brainstem tectum and orients the head more peripheral presses some sensory transmission to visual or auditory stimulation. The while within the spinothalamic tract in volun- lateral vestibulospinal tract originates temperature is tary movement. The proximity of the in the lateral vestibular nucleus (of more medially lateral corticospinal tract to the motor Deiters) and helps in maintaining the represented neurons that innervate distal limb mus- center of gravity for the body. The within this tract. cles supports its role in facilitating the raphespinal tract originates from its performance of skilled movements and nucleus in the medulla and modulates the belief that an isolated pyramidal le- sensory transmission from its position sion “only” results in flaccid paralysis within the Lissauer tract. The aminer- and loss of skilled motor function of the gic pathways arise from their cell distal limb muscles. groups within the pons and medulla

FIGURE 1-10 Anterior gray horn cell column and somatotopic organization. Reprinted with permission from Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. London: Saunders, 2007:192. Copyright © 2007, Elsevier.

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KEY POINT: and have inhibitory effects on sensory The anterior spinal artery arises Ⅲ The long descending neurons and facilitatory effects on mo- from the union of the anterior spinal tracts tor neurons through a widespread dis- branches of the vertebral artery and (corticospinal, tribution in the spinal cord gray mat- descends within the anterior median reticulospinal, ter. The central autonomic pathways fissure of the spinal cord down to the tectospinal, arise from the hypothalamus as well as conus medullaris. Its largest caliber is vestibulospinal, associated brainstem nuclei, terminat- at the lumbosacral area, and smallest raphespinal), ing on neurons within the intermedio- at the thoracic area, which is also con- and aminergic lateral cell columns. sidered its watershed area. The two and autonomic posterior spinal arteries also originate pathways will Vascular Supply of the Spinal from the vertebral arteries but descend terminate on Cord along the line of attachment of the interneurons, The arterial blood supply to the spinal dorsal nerve roots, posterolateral sul- which then cord comprises three longitudinally influence alpha cus, on either side. At the conus med- and gamma oriented vessels as well as contribu- ullaris, the anterior and posterior spi- motor neuron tions from numerous radicular vessels nal arteries communicate though function. (Bowen and Pattany, 1999). A rich vas- anastomotic branches (Figure 1-12). cular plexus (arterial or pia vasoco- Thirty-one pairs of small radicular rona or plexus) arises from anastomo- arteries enter every intervertebral fora- ses between these vessels along the men supplying their corresponding surface of the spinal cord and from nerve roots. Some of these are larger which medullary vessels penetrate and also supply the spinal cord, ra- into both the white and gray matter. diculomedullary branches. There may These penetrating vessels are end ar- be six to 10 such arteries, and through teries and do not anastomose further. their anterior radicular branch they contribute to the anterior spinal artery. The cervical and first two thoracic segments receive these arteries from branches of the vertebral and thyro- cervical trunk, T3 to T7 spinal cord usually from an intercostal artery, and the remainder of the spinal cord receives the largest and most constant artery of Adamkiewicz (arises from a left-sided intercostal or lumbar artery, 20 usually at the T9 through L2 spine level), which supplies the lumbar enlargement and conus medullaris. The posterior spinal arteries receive contri- butions from 12 to 16 posterior radicular arteries, including a radicular branch from the artery of Adamkiewicz. The intrinsic arterial supply of the spinal cord consists of a centripetal (posterior spinal arteries and the anterolateral plexuses) and a centrifugal FIGURE 1-11 Descending pathways (upper cervical level). (anterior sulcal arteries) system (Fig- Reprinted with permission from Fitzgerald MJ, Gruener ure 1-13). The centripetal system is G, Mtui E. Clinical neuroanatomy and neuroscience. 5th formed from radial arteries directed in- ed. London: Saunders, 2007:198. Copyright © 2007, Elsevier. ward and supplying the posterior white columns, and through shorter

Continuum: Lifelong Learning Neurol 2008;14(3) KEY POINTS: Ⅲ The majority of fibers that give rise to the corticospinal tract have their origin in primary motor cortex, but supplementary motor cortex and premotor cortex, as well as somatic sensory cortex, also contribute. Ⅲ Within the pyramidal decussation, 70% to 90% of fibers will decussate and give rise to the lateral corticospinal tract. A somatotopic organization develops with fibers to the sacral area most lateral and those to the cervical, medial. Ⅲ Thirty-one pairs of small radicular arteries enter every intervertebral foramen supplying their 21 corresponding FIGURE 1-12 Arterial supply of the spinal cord. nerve roots. Reprinted with permission from Moore KL, Dalley AF. Clinically oriented anatomy. Philadelphia: Some of these Lippincott William & Wilkins, 1999:487. are larger and also supply the spinal cord, radial penetrating vessels the periph- also contribute to the arterial vasoco- (radiculomedullary eral rim of perhaps one-third to one- rona that envelops the spinal cord and branches). There half of the spinal cord. The centrifugal through their short penetrating arteries may be six to 10 system arises from sulcal arteries of the supply the anterior rim of the spinal such arteries, and through anterior spinal artery that pass back cord. In general, the centrifugal system their anterior into the anterior medial sulcus and (anterior spinal artery) supplies the an- radicular branch then turn right or left to supply the terior two-thirds of the spinal cord. they contribute adjacent gray and white matter. Smaller Analogous to the arterial blood to the anterior branches from the anterior spinal artery supply, venous drainage of the spinal spinal artery.

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FIGURE 1-13 Arterial supply of a spinal cord segment. Reprinted with permission from Haerer AF. DeJong’s: the neurologic examination. 5th ed. Philadelphia: Lippincott Company, 1992:582.

cord also involves a longitudinal system of veins, the larger posterior spinal vein and the anterior. Through a cir- 22 cumferentially arranged venous anastomosis, coronal venous plexus, within the pia mater on the spinal cord’s surface, they are connected (Figure 1-14). The anterior spinal vein will communicate superiorly with the venous system of the brainstem and in- feriorly end at the dural sac in the sacrum. The posterior spinal vein communicates with radicular veins at Venous drainage of a spinal cord segment. the cervical level and extends down to FIGURE 1-14 the conus medullaris. At each spinal Krauss WE. Vascular anatomy of the spinal cord. Neurosurg Clin N Am 1999;10(1):9–15. cord segment small radicular veins drain the nerve roots, but at some lev- Reprinted with permission from Mayo Foundation for Medical Education and Research. All rights reserved. els larger veins, medullary veins, will arise from the anterior median spinal

Continuum: Lifelong Learning Neurol 2008;14(3) vein. There are approximately 10 to 20 anterior veins and a similar number of posterior medullary veins, asymmetric in location and not concomitant with the medullary arteries. The largest are in the lumbar region: the great anterior medullary vein (usually accompanying the nerve roots between T11 and L3) and the great posterior medullary vein usually at L1 or 2. The posterior half of the spinal cord will drain into the posterior and the anterior half into the anterior medullary veins. These medullary veins follow and FIGURE 1-15 Vertebral venous plexus. penetrate the dura with the nerve root Modified with permission from Moore KL, Dalley AF. Clinically oriented anatomy. Philadelphia: Lippincott and in the intervertebral foramen will William & Wilkins, 1999:466. unite with the radicular veins, internal and external vertebral plexus to form the intervertebral vein that drains blood with the intercostal veins and then via from the spine and spinal cord. Prior to the azygos and hemiazygous veins will their exit from the dura matter, these enter the superior vena cava. The re- veins are valveless (Gillilan, 1970; mainder of the venous drainage from Krauss, 1999). the spinal cord can follow a similar The cervical intervertebral veins pathway or, through the azygous and will drain into the deep cervical and hemiazygous veins, enter the common vertebral veins and will empty into the iliac veins and then the inferior vena superior vena cava through the bra- cava. chiocephalic and subclavian vein. At Within the spinal canal’s epidural the thoracic cord they will connect space is also a longitudinally and cir-

FIGURE 1-16 Cord transection (modalities involved). Reprinted with permission from Souayah N, Khella S. Neurology examination & board review. New York: McGraw Hill, 2005:44.

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cumferentially arranged anastomosis SPINAL CORD SYNDROMES of valveless veins, the internal venous plexus (anterior and posterior) (Figure A syndrome (symptom complex) rep- 1-15). It communicates with the spinal resents a complex of signs and symp- cord through the medullary and radicu- toms that appear in combination and lar veins, and vertebral body through a present as a clinical picture. It may basivertebral vein, but it also drains to a have a specific cause, disease, or in- separate plexus that surrounds the ver- herited abnormality, but this is not a tebra, the external vertebral plexus (an- requirement and at times has resulted terior and posterior divisions). Through in some confusion in the use and di- the previously mentioned routes, it will agnostic significance of the term. Some eventually empty into the superior or of the reported etiologies for the respec- inferior vena cava. tive syndromes are listed in Table 1-1.

TABLE 1-1 Spinal Cord Syndromes and Their Etiologies (Representative Examples)

Etiology Complete Cord Brown- Anterior Spinal Artery Transection Se´ quard Syndrome Syndrome

Vascular *Aortic dissection, *vasculitis, *atherosclerosis of the aorta

Inflammatory or *Postinfectious, infectious *multiple sclerosis, *postvaccinal Traumatic Traumatic spine *Traumatic injury, herniated disc spine injury Iatrogenic or Epidural hematoma Postoperative spine, aorta toxin (anticoagulants) or thoracic surgery, postoperative spinal 24 arteriovenous malformation surgery, decompression injury Metabolic

Endocrine Neoplastic Tumor, paraneoplastic Intramedullary tumors Degenerative or Cervical spondylosis Hereditary HTLV-I ϭ human T-cell leukemia virus I; HAM ϭ human T-cell lymphotropic virus–associated myelopathy.

*“Classic” or most common associated etiologies.

Continuum: Lifelong Learning Neurol 2008;14(3) KEY POINT: Complete Cord Transection the level of the lesion, the actual spinal Ⅲ In cord A complete cord transection disrupts cord level involved may be higher and transection, the the sensory tracts ascending from be- the presence of radicular pain or seg- most valuable low the level of the lesion and the mental paresthesias may serve as a finding that descending tracts from above (Figure more accurate localizer. Radiation of identifies the 1-16). However, as many such lesions pain may also occur, and with cervical spinal cord as the are incomplete, the clinical deficit will spinal cord lesions pain can radiate into site of the lesion is reflect the extent of the injury. On the arms, thoracic into the chest or ab- pinprick sensation. The actual spinal physical examination a sensory level domen, and lumbar or sacral spinal cord cord level involved will be detected, using pinprick loss, into the legs. Careful examination for may be higher; and is the most valuable finding that overlying vertebral spine tenderness the presence of identifies the spinal cord as the site of may suggest an underlying destructive radicular pain or the lesion. While sensory loss is ex- process such as a neoplasm or infection segmental pected to involve all modalities below as the etiology, and pain that lessens paresthesias may serve as a more accurate localizer.

Posterolateral Central Lesion Posterior Anterior Horn Combined Column Syndrome Column Cell Syndrome Anterior Syndrome Horn Cell Pyramidal Syndrome HIV HTLV-1 (HTLV– *Neurosyphilis Poliomyelitis, HTLV-1 associated myelopathy, West Nile virus HAM, or tropical spastic paraplegia) Late sequelae of Epidural spinal spinal cord injury cord compression

Nitrous oxide Postradiation myeloneuropathy

*Vitamin B12 deficiency Hexosaminidase *Copper deficiency deficiency myeloneuropathy

Intramedullary spinal cord tumors Cervical spondylosis *Syringomyelia *Spinal muscular *Amyotrophic atrophies lateral sclerosis (hereditary motor neuropathies)

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as anhidrosis, trophic skin changes, impaired temperature control, and vasomotor instability below the level of lesion can also be demonstrated (Cases 1-1 and 1-2).

Brown-Se´ quard Syndrome A hemisection of the spinal cord results in this characteristic syndrome (Tattersall and Turner, 2000) (Figure 1-17). Loss of pain and temperature sensation occurs contralateral to the side of injury due to interruption of the crossed spinothalamic tract, but usually a clinical sensory level is one or FIGURE 1-17 Hemisection of the cord (Brown-Se´ quard syndrome). two segments below the level of the lesion, reflecting the ascending nature Reprinted with permission from Souayah N, Khella S. Neurology examination & board review. New York: of this crossing tract (Nathan et al, McGraw Hill, 2005:46. 2001). Below the site of the lesion there is ipsilateral loss of proprioceptive function due to interruption of the with sitting or standing is suggestive of a ascending fibers of the posterior col- malignancy. While further historical de- umns, but such modalities of sensation tails may be helpful, laboratory and ra- may also arise from within the spino- diologic studies are necessary to more cerebellar tracts as well (Davidoff, definitively identify an etiology. 1989). Ipsilateral weakness below the Weakness, either paraplegia or tet- lesion reflects the interruption of the raplegia, occurs below the level of the descending corticospinal tract. In a lesion, owing to the interruption of the slowly progressing lesion hyperre- descending corticospinal tracts. Ini- flexia and an extensor toe sign will be tially, the paralysis may be flaccid and elicitable, while in an acute lesion areflexive because of spinal shock, but those findings may initially be absent. eventually, hypertonic, hyperreflexive Damage to the ventral roots or anterior paraplegia or tetraplegia occurs with horn cells results in segmental lower bilateral extensor toe signs, loss of su- motor neuron findings at the level of 26 perficial abdominal and cremasteric the lesion, but these are clinically dif- reflexes, and extensor and flexor ficult to identify in thoracic spinal cord spasms (Adams and Hicks, 2005). At lesions. Finally, if spinal root irritation the level of the lesion lower motor occurs, radicular pain, again at the site neuron signs (paresis, atrophy, fas- and side of the lesion, may be experi- ciculations, and areflexia) in a seg- enced and more clearly define the spi- mental distribution and reflecting nal cord level. damage to the local anterior horn cells or their ventral roots may be demon- Anterior Spinal Artery strated. These lower motor neuron Syndrome signs may be quite subtle in thoracic The vascular nature of this syndrome lesions but can localize a lesion to a is manifested in its abrupt onset with specific spinal cord level. Urinary and the deficit occurring within minutes or rectal sphincter dysfunction with in- hours from its initiation (Novy et al, continence, sexual dysfunction, and 2006). Clinically the syndrome pre- signs of autonomic dysfunction such sents with back or neck pain and at

Continuum: Lifelong Learning Neurol 2008;14(3) times in a radicular pattern, usually followed by a flaccid paraplegia and less commonly tetraplegia. Urinary and bowel incontinence are usually present. A sensory level to temperature and pinprick is found that reflects the involvement of the spinothalamic tracts bilaterally, but posterior column modalities of sensation remain relatively intact (Figure 1-18). Although FIGURE 1-18 Arterial spinal artery syndrome. the thoracic spinal cord may be an Reprinted with permission from Souayah N, Khella S. anatomic watershed zone with respect Neurology examination & board review. New York: to regional blood supply (Figure McGraw Hill, 2005:46. 1-19), the lumbosacral cord neurons appear to be more susceptible to ischemia (Duggal and Lach, 2002). The initial motor presentation progresses from a flaccid paraplegia to one of spasticity with hyperreflexia and Bab- inski signs (Case 1-3).

Central Lesions In this and in the syndromes discussed below, the underlying pathologic process is usually an insidious one, and the features of the disease develop over an extended period of time. When fully developed, the specific syndrome is more clearly recognized, but early during the process features may be incomplete, leading to difficulty and a delay in recognizing the syndrome. This syndrome results from a pathologic process in and around the central canal, initially involving those tracts that cross through the gray matter (anterior 27 and lateral spinothalamic tracts) (Figure 1-22). The resulting sensory impairment is termed a dissociated sensory loss (loss of pain and temperature sensation with preservation of position, vibration, and touch). The typical site of involvement in the cervical spinal cord and the particular sensory modalities initially involved result in a clinical presentation in which sensory loss occurs in a vest- or shawl-like pattern over FIGURE 1-19 Arterial supply of the spinal cord and the upper extremities and shoulders. As “watershed” areas. the size of the lesion increases, other fiber Reprinted with permission from Bradley WG, Daroff RB, tracts will be involved, dependent on the Fenichel GM, Marsden CD, editors. Neurology in clinical practice. Volume II. 3rd ed. Boston: Butterworth direction and extent of the pathologic pro- Heinemann, 1999:1226. cess. With extension anteriorly, a flaccid

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Case 1-1 A 64-year-old right-handed man was brought to the emergency department after having fallen down a flight of steps. He was not able to move his limbs. His medical history included coronary artery disease, status post–coronary artery bypass graft, diabetes mellitus, and schizophrenia, but no clear motor difficulties prior to this incident. He remembers that during the fall he hit his shoulders as he slid down the steps, but he experienced no loss of consciousness. Afterward he was aware of “pain all over,” but most of his discomfort was in both upper extremities and “electrical” in quality. Before being brought to the emergency department he noted that passive movements of his head intensified his upper extremity pain, but no associated worsening of his sensory symptoms occurred. On examination his vital signs were normal and he was in a rigid cervical collar. He had abrasions over both upper extremities. He was awake, alert, and followed all commands. His cranial nerve examination showed no clear abnormalities. He was able to shrug his shoulders but unable to lift his arms from the bed; proximal strength in the upper extremities was 2-3/5 and distal was 0/5. Lower extremity motor examination demonstrated weakness of hip flexion at 4-/5, and the other motor groups were 4/5. His tone appeared to be normal. Reflexes were depressed, but there appeared to be a right and perhaps a left extensor toe sign. Sensory examination demonstrated a decrease in pinprick up to the C4 level on the right and a patchy decrease in pinprick over the distal part of his left lower extremity; sacral sensation to pin was intact. Position sense appeared to be intact in his extremities. Rectal tone was normal; a urinary drainage catheter was in place. 28 FIGURE 1-20 Cervical spine MRI (sagittal view, T2 Routine cervical spine x-rays weighted). demonstrated no clear fractures or prevertebral soft tissue swelling. Extensive degenerative changes were noted at multiple levels. An MRI of the cervical spine demonstrated spinal stenosis, worse at C3-4, and neuroforaminal stenosis from C3 to C5. There was an increase in spinal cord T2 signal intensity from C3 to C5 without enhancement, which was interpreted as edema (Figure 1-20). Over the next 12 hours his lower extremity strength improved and his sensory deficits appeared to retract, but upper extremity strength remained significantly impaired. No improvement with steroids was noted. His persistent deficit and underlying cervical spine stenosis led to the recommendation for cervical spine surgery. Comment. Spinal cord trauma presents with different anatomic syndromes that include transection, cervicomedullary syndromes with high cervical spine lesions, anterior or posterior cord syndromes, Brown-Se´ quard syndrome, conus/cauda equina syndrome, or, as in this case, a central cord syndrome. Recovery and manifestations are related to the site and extent of the trauma and underlying mechanisms, eg, presence of preexisting spinal stenosis. These influence eventual outcome and dictate immediate management.

Continuum: Lifelong Learning Neurol 2008;14(3) Case 1-2 A 43-year-old woman with no prior medical history began to develop episodic vertigo and “jumpiness” in her eyes when she was in her late 30s. Attributed to vertigo, the symptom persisted but did not result in a disability. It was not until several years later that she began to notice numbness over both of her hands, unaccompanied by neck or radicular pain. She attributed this to carpal tunnel syndrome precipitated by her administrative and secretarial work. It was the gradual involvement of ambulatory difficulties and an acute worsening over the last several months that led her to seek further evaluation. Her general physical examination and vital signs were normal. Cervical spine examination and hairline were normal; there was no spinal scoliosis. Her cranial nerve examination demonstrated a left Horner syndrome, and rotary nystagmus was evident on horizontal as well as downward gaze. She had weakness predominantly in the distal lower extremities, more so on the left side and to a 4ϩ/5 degree, but her tone appeared to be increased in all extremities. Sensory examination showed a decrease in pinprick over the right extremity that extended onto the upper thorax; similar, but less- marked, findings were found on the left, suggesting a “shawl-like” pattern. Her reflexes were generally increased, and she demonstrated bilateral Babinski signs. An MRI scan of her brain and cervical spinal cord demonstrated a Chiari type-one malformation associated with syringomyelia. She underwent foramen magnum decompressive surgery, upper cervical spine laminectomy, and fusion and shunt placement (fourth ventricle to upper cervical spine). The postoperative cervical spine MRI scan FIGURE 1-21 Cervical spine MRI (sagittal view, T1 29 weighted). is shown in Figure 1-21. Since surgery her neurologic deficit has remained relatively stable, but recently she has begun to experience lower extremity radicular pain secondary to lumbar degenerative disc and neural foraminal stenosis. Comment. The insidious nature of this patient’s deficit initially delayed her seeking further clinical evaluation. However, the presence and pattern of her nystagmus, bilateral upper extremity sensory impairment, and cortical spinal tract involvement suggest an intramedullary spinal cord lesion that may extend into the brainstem. The onset of syringomyelia is often insidious, and symptom onset occurs between the ages of 25 and 40. A presentation with isolated findings may delay identification while the combination of brainstem dysfunction (eg, vertigo, oscillopsia, dysphonia, and facial sensory loss), dissociated sensory loss in the extremities, and later involvement of upper and lower motor neurons usually suggest the diagnosis. Radiologic confirmation is necessary for definitive diagnosis. Surgical interventions and extent are dependent on the assumed etiology and preexisting neurologic deficit. Decompression surgery or shunting procedures may be required in selected cases.

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KEY POINTS: Ⅲ The sensory impairment in Case 1-3 central cord A 67-year-old right-handed woman was brought to the emergency lesions is termed department by her husband. Without any clear precipitants, she had a dissociated awakened with severe low back pain, accompanied by radicular pain sensory loss (loss down both lower extremities, and abdominal discomfort. She had gone to of pain and her toilet but was unable to raise herself. While being transported to the temperature emergency department she developed urinary incontinence and later sensation with bowel incontinence. preservation of On evaluation, her vital signs and cardiac and vascular examinations position, were normal. Her examination was significant for lower extremity vibration, and paraplegia and hyporeflexia. Plantar stimulation elicited no response; a touch). Beevor sign was present. She demonstrated a sensory level to pinprick up to T10, decreased temperature to L1, and normal position sense. Sacral Ⅲ The lamination sensation to pinprick was absent; rectal tone was absent, and a urinary of the lateral drainage catheter was in place (initially 1000 cc of urine had been spinothalamic drained). There was no tenderness to percussion over the spine, and tract results in straight-leg raise was negative. Her pain resolved over 2 days. fibers conveying Steroids were initially administered because of the possibility of spinal sensation from cord compression, and an emergent MRI of the entire spine was the sacrum to be performed as well as imaging of the aorta. Both were normal. Over the more laterally/ ensuing weeks her lower extremity strength improved, and hyperreflexia, superficially as well as bilateral Babinski signs, appeared. However, her ambulation placed within remained impaired. Her sensory deficits lessened, and although her bowel the spinal cord. incontinence improved she required periodic urinary catheterization. These are often Comment. While this initial clinical presentation suggested a spinal cord preserved for an infarction and an anterior spinal artery syndrome, a compressive spinal extended period cord or conus/cauda equina lesion required exclusion. Aortic dissection can of time with also cause spinal cord ischemia/infarction, and such an evaluation is central spinal required as soon as possible. Usually (67%) of the time MRI demonstrates cord lesions a T2-weighted abnormality, but a normal study does not exclude a spinal (sacral sensory cord infarction, which then becomes a diagnosis of exclusion. Back or neck sparing). pain and radicular pain can occur at symptom onset (59%), resolving in several days, but later neurogenic pain can develop. In the majority of spontaneous cases (70%) an etiology is not discovered, but the possibility of mechanical stress-induced vascular compromise has been suggested in some cases. Prognosis is related to the extent of the injury, but ambulation usually remains impaired (Novy et al, 2006). 30

paralysis with fasciculations and atrophy with central spinal cord lesions, represent- occurs as the anterior horns and their mo- ing a form of sacral sensory sparing. tor neurons are affected. Lateral extension At times an acute cervical spinal involves the corticospinal tracts, resulting cord injury, especially after hyperex- in spastic paralysis of muscles below the tension injuries of the neck, results in a lesion, while posterior extension involves unique neurologic presentation that the posterior columns with disruption of signifies an injury to the central por- their sensory modalities. The lamination of tion of the spinal cord (distinguished the lateral spinothalamic tract results in fi- from the man-in-the-barrel syndrome bers conveying sensation from the sacrum reported after ischemic cerebral le- to be more laterally/superficially placed sions within the border zone between within the spinal cord and are often pre- anterior and middle cerebral arteries served for an extended period of time and cruciate paralysis, a syndrome of

Continuum: Lifelong Learning Neurol 2008;14(3) brachial diplegia after medullary lesions). Such individuals at first may be quadri- plegic, but recovery of lower extremity strength often occurs early, and the prognosis may be better because of a predominantly white matter injury (Col- lignon et al, 2002). However, a unique pattern of weakness that is more pro- nounced in the arms, worse distally than proximally, characterizes the syndrome and the unique site of injury. Urinary dysfunction, as well as patchy sensory loss below the level of the injury or upper and lower levels of sensory loss (sus- pended sensory level), can be demonstrated (Cases 1-1 and 1-2). FIGURE 1-22 Syringomyelia (modalities involved). Reprinted with permission from Souayah N, Khella S. Neurology examination & board review. New York: McGraw Hill, 2005:45.

Posterolateral Column Posterior Column Syndrome Syndrome A process involving the posterior columns Involvement of the posterior and lateral is characterized by loss of position sense, columns of the spinal cord will lead to a vibration sense, and two-point discrimina- pattern of sensory loss that predominantly tion. These deficits occur distal to the le- involves the modalities of position and vision. The lack of proprioceptive informa- bratory sense and a motor syndrome of tion and feedback to the motor system spastic paralysis that reflects involvement affects those muscle groups required for of the corticospinal tract (Figure 1-23). discriminative movements, resulting in a This pattern of dysfunction leads to a sen- sensory ataxia. While vision can partially sory ataxia with a positive Romberg sign, compensate for this loss of proprioceptive while pain and temperature sensation re- information when the eyes are open, main intact because of preservation of the ataxia worsens when they are closed, re- spinothalamic tracts. A spastic-ataxic gait sulting in the presence of a Romberg sign. reflects this constellation of fiber tract dys- The gait is described as ataxic (or stomp- function. 31 This pattern of involvement usually develops insidiously, reflecting the underlying pathologic processes. In the syndrome known as subacute combined degeneration, related to a deficiency of vitamin B12 or copper, the initial neurologic manifestations may be those of limb paresthesia, predominantly involving the feet, followed later by the development of the more distinctive posterior column and FIGURE 1-23 Posterolateral column syndrome. corticospinal tract deficits. The complete Reprinted with permission from Souayah N, Khella S. Neurology examination & board review. New York: features of this syndrome usually de- McGraw Hill, 2005:44. velop over an extended period of time.

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KEY POINTS: Ⅲ Dysfunction in the posterior column syndrome is characterized by a sensory ataxia with a positive Romberg sign while pain and temperature FIGURE 1-24 Combined anterior horn cell–pyramidal sensation remain syndrome. intact because Reprinted with permission from Souayah N, Khella S. of preservation Neurology examination & board review. New York: of the McGraw Hill, 2005:44. spinothalamic tracts. Ⅲ ing) in character, and the deficit can be cell bodies of the sympathetic neurons are With more prominent in darkness or with eye involved. dysfunction of closure as visual cues no longer can assist the posterior in maintaining balance. The affected limbs Combined Anterior Horn Cell– columns in the Pyramidal Syndrome cervical region, may become hypotonic but usually are not weak. At times other spinal cord le- This syndrome is perhaps best exempli- neck flexion may fied by ALS. These lesions produce a com- elicit an electric- sions can produce a truncal ataxia but bination of flaccid and spastic paralysis. like sensation without the associated proprioceptive dif- that radiates ficulties. In such cases, spinocerebellar Damage to the anterior horns or lower down the back tract dysfunction, as a manifestation of spi- motor neurons will result in a flaccid pa- or into the arms nal cord compression, appears to be re- ralysis with atrophy and fasciculations, (Lhermitte sign). sponsible for this clinical syndrome. while a lesion of the lateral corticospinal With dysfunction of the posterior col- tract or upper motor neurons results in a umns in the cervical region, neck flexion spastic paralysis with associated hyperre- may elicit an electric-like sensation that flexia and Babinski sign (Figure 1-24). radiates down the back or into the arms The degree of injury to either site can be (Lhermitte sign). It is thought to represent highly variable and reflected in the clinical increased mechanosensitivity of the dorsal presentation. If one site is more or pre- columns with neck flexion further activat- dominantly affected, an additional lesion ing those sensory pathways. The symp- in the other at the same level may not 32 tom is most frequently associated with spi- produce noticeable effects. nal cord involvement in multiple sclerosis. INTRAMEDULLARY VERSUS Anterior Horn Cell Syndrome EXTRAMEDULLARY CORD Damage to the motor anterior horn cells LESIONS leads to an ipsilateral flaccid paralysis ac- Neoplasms arising within the spinal companied by atrophy and fasciculations. canal tend to produce their symptoms Because larger muscles are supplied by and signs in a slow and progressive motor neurons from more than one seg- manner, although an acute presenta- ment, damage to a single spinal cord seg- tion can occasionally be encountered. ment may lead only to muscular weak- When arising from lesions within the ness rather than complete paralysis of the spinal cord (intramedullary), symp- affected motor group (Figure 1-10). toms often begin within the vicinity of When the lateral horns are involved, a the central canal. Sensory symptoms decrease in sweating and vasomotor func- are initially less localizing and dissoci- tions may also be demonstrated, as the ation of sensory loss can occur. Early

Continuum: Lifelong Learning Neurol 2008;14(3) KEY POINT: Ⅲ A more TABLE 1-2 Clinical Features of Intramedullary Versus Extramedullary Spinal Cord Lesions symmetric pattern of sensory loss and Symptoms and Extramedullary Intramedullary motor Signs dysfunction is Spontaneous pain Radicular in type and Burning in type and more consistent distribution; an early poorly localized with a conus and important than a cauda symptom equina lesion. Sensory deficit Contralateral loss of Dissociation of pain and temperature; sensation; patchy ipsilateral loss of distribution proprioception Changes in pain and More marked than at Less marked than at temperature level of lesion level of lesion sensations over perineum (saddle area) Lower motor neuron Segmental Widespread with involvement atrophy and fasciculations Upper motor neuron Prominent, early Late, minimal involvement Muscle stretch reflexes Increased early, Late, minimal changes markedly Corticospinal tract Early Late signs Trophic changes Usually not marked Marked

Data from Brazis PW, Masdeu JC, Biller J. Localization in clinical neurology. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2007:111. Data from Haerer AF. DeJong’s the neurologic examination. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 1992:588.

evidence of lower motor neuron find- Brown-Se´quard pattern may appear. ings, later accompanied by corticospi- The features of either type of clinical 33 nal tract findings, characterizes these syndrome are described and con- lesions, and their clinical presentation trasted in Table 1-2. can mimic a syrinx. Extramedullary lesions can arise from the dura and CONUS MEDULLARIS VERSUS adjacent structures (extramedullary CAUDA EQUINA LESIONS intradural) or can have an extradural The close anatomic localization of the co- site of origin such as the vertebral bod- nus medullaris and overlying cauda ies or extradural space (extramedul- equina makes distinction of either syn- lary extradural). Spontaneous pain, drome difficult, and at times involvement especially in a radicular pattern, can of both structures occurs. A symmetric be a presenting feature and suggests pattern of sensory loss and motor dysfunc- the level of involvement. Subsequent tion is more consistent with a conus than a motor and sensory changes are usually cauda equina lesion. The clinical features slow to develop, and because of the of both conditions are further described asymmetric nature of such lesions a and contrasted in Table 1-3.

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TABLE 1-3 Clinical Features of Conus Medullaris and Cauda Equina Lesions

Symptoms and Conus Medullaris Cauda Equina Signs Spontaneous pain Not common or May be most severe; bilateral and prominent symptom; symmetric; over severe and radicular in perineum and thighs type; unilateral or asymmetric; over perineum, thighs, legs, and back Sensory deficit Saddle distribution; Saddle distribution; bilateral, usually may be unilateral and symmetric; dissociation asymmetric; all of sensation modalities affected; no dissociation of sensation Motor loss Symmetric; not Asymmetric; more marked; fasciculations marked; atrophy may may be present occur; usually no fasciculations Reflex loss Only Achilles reflex Patellar and Achilles absent reflexes may be absent Bladder and rectal Early and marked Late and less marked symptoms Trophic changes Decubitus common Decubitus less marked Sexual function Erection and Less marked ejaculation impaired impairment Onset Sudden and bilateral Gradual and unilateral

Data from Brazis PW, Masdeu JC, Biller J. Localization in clinical neurology. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2007. Data from Haerer AF. DeJong’s the neurologic examination. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 1992:591.

Continuum: Lifelong Learning Neurol 2008;14(3) REFERENCES AND SELECT READINGS Note: There are many general textbooks of neuroscience, neuroanatomy as well as clinical neurology that you may have found useful. The following recom- mendations represent our “bias” and are driven by familiarity with and the usefulness we have found in the following general resources for teaching and review.

Adams MM, Hicks AL. Spasticity after spinal cord injury. Spinal Cord 2005;43(10):577–586.

Bowen BC, Pattany PM. Vascular anatomy and disorders of the lumbar spine and spinal cord. Magn Reson Imaging Clin N Am 1999;7(3):555–571.

Bradley WG, Daroff RB, Fenichel GM, Marsden CD, editors. Neurology in clinical practice. Volume II. 3rd ed. Boston: Butterworth Heinemann, 1999:1226.

Brazis PW, Masdeu JC, Biller J. Localization in clinical neurology. 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2007.

Collignon F, Martin D, Le´ nelle J, Stevenaert A. Acute traumatic central cord syndrome: magnetic resonance imaging and clinical observations. J Neurosurg 2002;96(1 suppl):29–33.

Davidoff RA. The dorsal columns. Neurology 1989;39(10):1377–1385.

Duggal N, Lach B. Selective vulnerability of the lumbosacral spinal cord after cardiac arrest and hypotension. Stoke 2002;33(1):116–121.

Fitzgerald MJ, Gruener G, Mtui E. Clinical neuroanatomy and neuroscience. 5th ed. London: Saunders, 2007.

Gillilan LA. Veins of the spinal cord. Anatomical details; suggested clinical applications. Neurology 1970;20(9):860–868.

Grant JCB. An atlas of anatomy. 6th ed. Baltimore: Williams & Wilkins, 1972.

Haerer AF. DeJong’s the neurologic examination. 5th ed. Philadelphia: Lippincott, Williams & Wilkins, 1992.

Krauss WE. Vascular anatomy of the spinal cord. Neurosurg Clin N Am 1999;10(1):9–15.

Moore KL, Dalley AF. Clinically oriented anatomy. Philadelphia: Lippincott Williams & Wilkins, 1999. 35

Nathan PW, Smith M, Deacon P. Vestibulospinal, reticulospinal and descending propriospinal nerve fibres in man. Brain 1996;119(pt 6):1809–1833.

Nathan PW, Smith M, Deacon P. The crossing of the spinothalamic tract. Brain 2001;124(pt 4):793–803.

Nathan PW, Smith MC, Deacon P. The corticospinal tracts in man. Course and location of fibres at different segmental levels. Brain 1990;113(pt 2):303–324.

Novy J, Carruzzo A, Maeder P, Bogousslavsky J. Spinal cord ischemia: clinical and imaging patterns, pathogenesis, and outcomes in 27 patients. Arch Neurol 2006;63(8): 1113–1120.

Souayah N, Khella S. Neurology: examination & board review. New York: McGraw Hill, 2005.

Tattersall R, Turner B. Brown-Se´ quard and his syndrome [erratum published in Lancet 2000;356(9226):344]. Lancet 2000;356(9223):61–63.

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