{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.