{Spinal Cord

Anatomy and Neuroimaging

RITE Exam Review LectureErik Beltran, MD MS01/12/2015

Basic Anatomy Embryology Vascular Supply Grey Matter White Matter Clinical Cases & Neuroimaging

Lecture Outline

Spinal CordThe Basics

40-50 cm in length 1 – 1.5 cm in diameter 31 paired roots Ends at the L1-L2 as the

conus medullaris Cauda equina continues

as collection of lumbosacral nerves

Filum terminale C1-C7= Above vertebrae C8 & below= Below

vertebrae

Spinal CordEmbryology

Formed from the caudal third of the neural tube w/ neuralization beginning day 17

Caudal neuropore closes by day 27 Alar Plate- Dorsal horns, afferent function Basal Plate- Ventral & lateral horns, efferent

function & ventral roots

Growth increases during the 3rd embryonic month Vertebral column and spinal cord initially grow at the

same rate After 3rd month, spinal cord growth rate slows

compared to body and vertebral column Net result- Cord ends at L1-L2, but nerve roots still

exit at corresponding vertebrae

Spinal CordEmbryology

Cord is covered by the meninges

Dura matter- Tough outer covering, dural sac ends at S2.

Arachnoid Pia- Remains closely

adherent to the spinal cord. Filum terminale anchors the cord to the coccyx

Spinal cord is attached to the dura by a series of lateral denticulate ligaments

Spinal CordMeninges

-Skin-Subcutaneous Fat-Supraspinous ligament-Intraspinous ligament-Ligamentum flavum-Epidural fat-Dura-Arachnoid

What are the layers traversed when performing a lumbar puncture?

Spinal CordBlood supply

One anterior spinal artery Supplies anterior 2/3 of the spinal cord Arises from the vertebral arteries in the cervical region

and from 5-10 larger radicular arteries (off aorta) in the lower cord

Spinal CordBlood Supply

Two posterior spinal arteries Supply the posterior 1/3 of the spinal cord Arise from smaller radicular arteries at each level Largest radicular artery is the artery of Ademkiewicz

Spinal CordGrey Matter

Spinal CordGrey Matter – Rexed lamina

Defined by cellular structure & location

I-VI – Dorsal horn VII & X -

Intermediate zone VIII & IX – Ventral

horn

Spinal CordGrey Matter – Rexed lamina I - V

Lamina I (marginal nucleus of the spinal cord) Lamina II (substantia gelatinosa) Lamina III - V (nucleus proprius)

Found at all cord levels Receive information from Lissauer’s tract

(contains ipsilateral pain and tempurature afferents, which ascend 1-2 segments, then synapse

Spinal CordGrey matter - Rexed Lamina VI

Lamina VI (Nucleus dorsalis/ Clark’s nucleus)

Extends from C8 – T3/T4 Major relay center for unconscious proprioception Receives information from muscle spindle and golgi

tendon organs and projects to the cerebellum via the dorsal spinocerebellar tract

Spinal CordGrey matter - Rexed Lamina VII

Lamina VII (Intermediolateral nucleus & sacral parasympathetic cell bodies)

Extends from T1 – L2 Cell bodies of 1st order sympathetic neurons

Sacral parasympathetic cell bodies: S2 – S4

Spinal CordGrey matter

Lamina X – Anterior white commissure & central canal

Lamina VIII - Contains primarily interneurons

Spinal CordGrey Matter – Rexed Lamina IX

Contains mainly motor neurons Alpha motor neurons innervate a single motor unit Dorsal motor neurons tend to innervate flexor muscles

compared to extensors, which tend to be more ventral Gamma and beta motor neurons innervate muscle spindles

Cell bodies of the phrenic nerve (C3-C5) Spinal accessory nucleus (C1-C6) Onuf’s nucleus (S2-S4) – Motor neurons that are associated

with urethral and anal sphincters. Contribute to maintenance of micturation and defecation continence.

Spinal CordSummary of grey matter

Substantia gelatinosa – Relay center for spinothalamic tracts

Nucleus dorsalis – Relay center for proprioception Intermediolateral nuclei – Sympathetic neurons Motor neurons – Innervate motor units

Spinal CordWhite matter – Ascending & Descending pathways

Spinal CordWhite matter – Ascending pathways

Dorsal columns Spinothalamic tract Spinocerebellar tracts

Spinal CordWhite matter – Ascending pathwaysDorsal Columns

Somatotropically organized, medial to lateral: Sacral, Lumbar, thoracic, cervical.

Comprised of 1st order afferent axons containing well localized fine touch and conscious proprioceptive information.

Remain ipsilateral throughout spinal cord. Synapse in nucl gracilis & cuneatus in the

medulla.

Spinal CordWhite matter – Ascending pathwaysAnterolateral System

Lateral spinothalamic tract Contains contralateral pain and temperature

information. 2nd order neurons that have arisen from the

posterior grey matter (substantia gelatinosa, etc) and cross via anterior commissure.

Medial to Lateral: C/T/L/S Destination: mainly thalamus (VPL)

Also: Spinoreticular system (arousal to painful stimuli) Spinotectal system (orient head & eyes to painful

stimuli)

Spinal CordWhite matter – Ascending pathwaysSpinocerebellar Tracts

Division From (peripheral process)

Region

Dorsal spinocerebellar

Muscle spindles (primary)

Ipsilateral trunk and legs

Ventral spinocerebellar

Gogli tendon organs Ipsilateral trunk and legs

Cuneocerebellar Muscle spindle (primary)

Ipsilateral arm

Rostral spinocerebellar

Golgi tendon organs Ipsilateral arm

Spinal CordWhite matter – Descending pathways Lateral and anterior corticospinal tracts

Motor pathways Anterior corticospinal tract:

~ 10 % of descending motor axons, primarily truncal muscles.

Ends by mid-thoracic cord. Ipsilateral until axons cross to anterior horn at

the level of the synapse. Lateral corticospinal tract:

~ 90% of descending motor axons. Contains contralateral axons.

Spinal CordWhite matter – Descending pathways Rubrospinal Tract

Contributes to control of large muscle movements in the arms

Primarily modulates flexion movements of arms Lesions above the Red Nucleus lead to decorticate

posturing Disinhibition of rubrospinal tract with disruption of

lateral corticospinal tracts = Flexion of upper extremities.

Decerebrate posturing results from a lesion below the red nucleus.

Spinal CordWhite matter – Descending pathways Vestibulospinal & Tectospinal Tracts

Vestibulospinal: Alters muscle tone, position of limbs and posture in

response to movements of the head and body. Medial tract acts to stabilize head and neck. Lateral tract acts to stabilize extensors of the legs.

Tectospinal: Mediates reflex postural movements of the head & neck in

response to Visual & Auditory stimuli

Spinal Cord Cases

A 34 year-old male is stabbed in the back after telling a friend he was going to vote for Trump.

Your careful neurologic exam reveals: Right leg weakness with right extensor plantar

response. Loss of vibration and proprioception at the right toe

and ankle. Loss of pain and temp of the left leg and left torso

to T6. Where is the lesion?

Brown-sequard syndrome

Spastic/weak leg w/ impaired joint position sense, & loss of contralateral pain/temp 2-3 segments below spinal lesion

58 yo male with cardiac disease undergoes repair of abdominal aortic aneurysm.

8 hours later, he wakes up with no movement of his legs, the cardiothoracic surgeons swear it wasn’t them..

After obtaining a CT of the head, the primary team activates the stroke pager…

Your neurologic exam finds: Paraplegia, hypotonia, areflexia at patella/achilles, absent

pain & temp to T11-T12, w/ preserved vibration and proprioception.

Where is the likely lesion and from what pathologic process? Why did you find hypotonia and areflexia?

Anterior Spinal Artery Occlusion

Anterior Cord syndrome. Lesion most likely due to insufficient arterial flow

to the anterior spinal cord at the artery of Adamkiewicz.

Loss of reflexes and low tone are commonly seen due to spinal shock in an acute injury.

Reflexes may not return for days to weeks. Eventual development of spasticity and

hyperreflexia.

28 yo female presents to your clinic with severe headaches exacerbated by sneezing, coughing, bending over or defecation.

Your careful neurologic exam notes diminished pain and temperature over the bilateral C4 and C5 dermatomes…

What is the pathologic process?

Central Cord Syndrome

Syringomyelia and Chiari malformation.

Loss of pain / temp in a cape-like distribution.

Preserved vibration / posterior column sensation and motor systems until late in disease course.

45 yo male presents with low back pain, urinary retention, lower extremity weakness.

Your careful neurologic exam notes saddle anesthesia, brisk patellar reflexes, increased tone in lower extremities, 4/5 strength in lower extremities, increased anal sphincter tone.

Likely localization and cause?

Conus medullaris syndrome (lesion at L1-L2) from a ruptured lumbar disc.

Numbness and weakness tend to be symmetric. Mixture of upper and lower motor neuron signs. Urinary retention, erectile dysfunction, constipation

(increased anal sphincter tone).

Cauda equina syndrome More likely to be asymmetric Only lower motor neuron signs. Low anal sphincter tone and low urethral tone lead to

early urine and fecal incontinence.

56 year-old male reports weakness of right arm for 6 months, followed by weakness of right leg for 3 months.

Neurologic exam notes 4/5 strength throughout RUE, 4+/5 strength in RLE, with right sided hyperreflexia, atrophy and fasciculations.

Amyotrophic lateral sclerosis

Hallmark: Weakness & Wasting in the setting of preserved or brisk reflexes.

Important to note that while fasciculations derive from LMN, they are not necessarily pathologic when seen in isolation.

Spinal Cord Neuroimaging

Spondylolysis

Spondylolisthesis

Cervical disc herniation

Cord contusion is the best response because there is gross traumatic injury to the spinal column with disruption of the C4-C5 ligamenta flava, interspinous ligaments, and posterior longitudinal ligament. There is fracture deformity of C5 vertebra consistent with a flexion teardrop fracture and fracture of C6. There is prevertebral soft tissue edema, and the cord has T2 hyperintense signal at the C5 and C6 level consistent with traumatic cord contusion with some intramedullary hemorrhagic component. Neuromyelitis optica, ependymoma, abscess, and sarcoid myelitis are not the best choices because the extensive vertebral column injuries are not consistent with the typical presentation of any of these entities.

Spondylodiscitis with epidural abscess

The spinal lesion is multisegmental, elongated, and is in the lower cervical and thoracic levels. The pattern and extent of this lesion is atypical for multiple sclerosis in its size and extent and most characteristic of a form of transverse myelitis. The presence anti aquaporin antibodies (NMO antibodies) is a diagnostic marker of neuromyelitis optica (also known as Devic disease) which is a distinct form of demyelinating disease. The other choices would be highly unlikely to have these auto-antibodies.

The arrows on the two images point to a semilunar nodule along the right anterior margin of the right facet joint. This structure results in right lateral recess stenosis and is a frequent etiology of radicular pain in the elderly. This structure arises continuous with the right facet joint and is typical of a synovial cyst, likely partially calcified. A neurofibroma would be more likely seen within the right neuroforamen arising along the nerve root. A large free fragment with that dimension and that location is unlikely. The structure is adjacent to, but does not appear to be continuous with the adjacent disc.

The figures demonstrate a diffuse heterogeneous appearance of the vertebrae, "salt and pepper pattern". There is also a larger focal enhancing lesion extending into the pedicle of L2 along with compression fractures. This pattern of diffuse osseus invasion can be seen due to hematologic diseases and is most typical of multiple myeloma. Thalassemia is associated with marrow reconversion with the repopulating of yellow marrow by hematopoietic cells, but that would not be expected to show this salt and pepper pattern or a focal lesion as in L2, nor would metastatic carcinoma. There are pathologic compression fractures and some kyphotic posturing, but these would not be the best answers.