Pathology of Spinal Cord and PNS Flashcards
Corticospinal tract
Consist of upper motor neurons that project from premotor areas and motor cortex (precentral gyrus) to motor neurons and interneurons in the spinal cord.
Lateral tract decussates at medullary pyramids and make up majority of motor fibers.
Anterior tract decussates at spinal level of innervation to control axial muscles.
Anterior Spinal Cord Syndrome aka Beck’s Syndrome (spinal cord syndrome)
Commonly caused by disruption of supply by aorta, usually from atherosclerosis, aneurysm/dissection, direct trauma, abdominal surgeries.
Results in ischemic infarction of anterior 2/3 of spinal cord –> compromised bilateral corticospinal and spinothalamic tracts but spared posterior column.
Loss of motor function and pain/temperature below level of injury with preserved fine touch/conscious proprioception.
Brown-Sequard Syndrome aka hemiparaplegic syndrome
Damage to lateral one HALF of spinal cord–a “hemisection.”
Ipsilateral loss of motor function, fine touch, conscious proprioception.
Contralateral loss of pain/temperature.
Central Cord Syndrome (spinal cord syndrome)
Damage to central gray matter and central tracts
Tract fibers innervating upper limbs more centrally located –> greater deficits in upper vs. lower.
Variable sensory loss.
Amyotrophic Lateral Sclerosis (ALS) aka Lou Gehrig’s (neurodegenerative disease of motor neurons)
Molecular, gross, microscopic findings?
Degeneration of upper and lower motor neurons, cases of which majority are sporadic with small percentage inherited.
Cell bodies located in brain and to target lower motor neurons via the corticospinal tracts –> UMN signs
Cell bodies located in anterior horn of spinal cord to target muscles/glands –> LMN signs
Cytoplasmic accumulation of protein-rich inclusions reactive with TDP-43. Also seen in frontotemporal lobar degeneration.
Grossly would see atrophy of anterior horns. Brain typically normal but may see atrophic precentral gyrus due to UMN degeneration..
Microscopic findings include loss of motor neuron fibers with astrogliosis in motor cortex, brainstem, and spinal cord. Cytoplasmic eosinophilic Bunina bodies.
Different categorization of spinal muscular atrophies
Large heterogeneous group of rare debilitating disorders characterized by LMN degeneration.
Prototype is spinal muscular atrophy (SMA) of AR inheritance pattern. Prototype of SMA is Werdnig-Hoffman Disease (SMA1).
Another form of the spinal muscular atrophIES is XLR inherited Kennedy’s disease.
Spinal Muscular Atrophy (SMA)
Autosomal recessive defect of SMN1 gene on chromosome 5.
Proximal/respiratory muscles usually affected first.
Werdnig-Hoffman Disease (SMA1) aka “floppy baby syndrome”
Gross and microscopic findings
Prototype of SMA.
Abrupt manifestation of symptoms in first months of life that quickly progresses to respiratory failure–death within 1-2 years without mechanical ventilation.
Gross findings - atrophic anterior roots and skeletal muscles
Microscopic findings - loss of LMN in spinal cord and brainstem; rounded atrophic fibers with scattered normal/hypertrophic fibers
Kennedy’s Disease
XLR CAG expansion of first exon of androgen receptor–note CAG repeat also seen in Huntington’s but mode of inheritance is AD.
Generally middle adult life onset.
Neuromuscular and endocrine manifestations:
- Spinal and bulbar muscular atrophy –> LMN signs
- Gynecomastia, ED, reduced fertility
Poliomyelitis
LYTIC infection of LMN of anterior horn by small RNA enterovirus –> flaccid paralysis, neuronophagia (microglial proliferation surrounding infected neuron) that becomes cellular nodules
Fecal-oral transmission
Tabes dorsalis
Demyelination, caused by tertiary syphilis, of posterior column
Friedreich’s Ataxia
Degenerative disorder of cerebellum and multiple spinal tracts due to AR expansion of GAA of frataxin gene on chromosome 9.
Cerebellar degeneration –> ataxia
Posterior column –> conscious proprioception, fine touch
Lateral corticospinal tract –> LMN symptoms
Lateral spinothalamtic tract
Subacute Combined Degeneration aka Lichtheim’s Disease
Degeneration of posterior and lateral columns, histologically similar to Friedreich’s, due to B12, vitamin E, and copper deficiency
Myxopapillary Ependymoma
Almost exclusively in conus medullaris/cauda equina/ filum terminale region
Generally teenagers/young adults p/w back pain
Well circumscribed lesions with cuboidal to elongated cells radiating from central vascularized core amongst myxoid matrix in microcysts
Charcot-Marie-Tooth Disease (CMT)
Hereditary motor and sensory neuropathies–most commonly inherited neurological disorder
CMT1 caused by duplication of region on chromosome 17 that includes peripheral myelin protein 22 (PMP22) gene.
Foot drop is CLASSIC initial presentation, along with foot deformities, distal muscle atrophy, sensory loss
Similar to CIDP, see onion bulb formation due to recurrent demyelination/remyelination
