BB Lecture 11 Spinal Cord Syndromes Flashcards
Descending Corticospinal tract
- 90% of descending motor pathways decussate (cross) at the level of the pyramids in the medulla and descend into the lateral corticospinal tract
- arm fibers travel medial, leg fibers travel lateral
- descending fibers exert an inhibitory influence on muscle tone and deep tendon reflexes (DTRs)
Ascending spinothalamic tract
Anterolateral system; responsible for pain, temperature and light touch
- runs on Lissauers tract
- crosses at the ventral white commissure (the central canal in the spinal cord segment)
- synapses in the thalamus (ventroposterior lateral nucleus of the thalamus, VPL), then to the somatosensory cortex
- leg fibers travel laterally and arm fibers travel medially (because arm fibers are adding to the spinal cord segment)
Ascending Dorsal columns (medial lemniscus)
responsible for proprioception, virbration, 2 point
-leg fibers travel medially in gracilis and arm is laterally in cuneatus (so opposite)
This is so because gracilis is L2 and up and cuneatus doesn’t start until T2…so cuneatus is when arms are adding their fibers
-ascends up to the lower medulla to terminate in the nucleus gracilis and nucleus cuneatus
-decussation occurs in the lower medulla
-fibers ascend then as the medial lemniscus to the thalamus (VPL), which projects to the primary somatosensory cortex
Sympathetic Pathway
Arise in hypothalamus
Descend ipsilaterally to synapse on the T1-L2 spinal nerves and innervate ipsilateral end organs
Horner’s Syndrome
Example of Sympathetic lesion; ptosis, miosis, anhidrosis;
Cocaine test
-cocaine drips into the eye, you get more stimulation and the pupil large
-if you drop cocain in the eye and there is NO dilation, then there is something fucked up and you have horners
Parasympathetic control
Also affected in spinal cord lesions
Infantile bladder
it fills then empties
Bladder control
under parasympathetic control (detrusor muscle)
- afferent: stretch receptors in smooth muscle wall of bladder send sensory input S2-S4 dorsal roots
- efferent: cell bodies in gray matter of S2-S4 spinal cord segments, parasympathetic stimulation causes contraction of the detrusor muscle in the bladder wall and bladder emptying occurs
- in order for you to fuck up bladder control, lesions need to be BILATERAL
Lesion above pons (in relation to bladder)
Infantile bladder (when bladder fills, reflex empties)
Arterial supply of the spinal cord
Anterior 2/3: supplied by the anterior spinal artery which arises from the vertebral artery
Posterior 1/3: supplied by paired posterior spinal arteries
UMN Symptoms and Signs
- slowness/stiffness (think of hand in contracted state in video…)
- increase tone (spasticity)…spasticity = stiffness
- hyperactive reflexes
- Pathological reflexes such as extensor plantar or Babinski, Hoffman’s, palmomental, pseudobulbar affect
LMN Symptoms and Signs
-weakness and cramps
-Atrophy
-Fasciculations (not the same as spasticity)
-Decreased tone
-Hypoactive Reflexes
ATROPHY especially a sign that you have lost your ventral roots
Complete Cord Transection
MOA:
-trauma
-extrinsic compression (tumor,, abscess, hematoma)
-transverse myelitis (inflammatory)
Outcome depends on level of lesion
-high cervical lesions (C1-C3) require ventilator support
-Sparing C7 retains ability to independently transfer (elbow and wrist extension)
Brown-Sequard Syndrome
Hemisection of the spiinal cord
MOA:
-caused by trauma or extrinsic lesion
-rarely caused by intramedullary lesion
Central Cord Lesions
Caused by syringomyelia, hematomyelia, intramedullary tumor, chiari malformation (which leads to syringomyelia)
Symptoms: BILATERAL lesion of the spinothalamic tract at FIRST
NEXT affects anterior horn cells at level of lesion with LMN findings
Cord damage starts centrally and spreads centrifugally (think of fluid filled hole near central cord of spinal cord)