Neuroscience Week 3: Spinal Cord Lesions

Question 1

Spinal Muscular Atrophy Clinical Features

Answer 1

Congenital degeneration of anterior horns of spinal cord

LMN lesions only, symmetric weakness

Floppy Baby with marked hypotonia (flaccid paralysis)

tongue fasciculations

Autosomal recessive inheritance of mutation in SMN1

SMA type 1 is called Werdnig-Hoffmann disease

Question 2

Spinal Muscular Atrophy

Spinal Lesion Location

Answer 2

• LMN lesions only by degeneration of anterior horns of spinal cord

Question 3

Werdnig-Hoffmann disease AKA

Answer 3

Spinal muscular atrophy Type 1

Question 4

Amyotrophic Lateral Sclerosis Clinical Presentation & Pathophysiology

Answer 4

Combined UMN (corticobulbar/corticospinal) and LMN (medullary and spinal cord) degeneration

No sensory or bowel/bladder deficits

Can be caused by a defect in superoxide dismutase 1

LMN deficits due to anterior horn cell involvement (dysarthia, dysphagia, asymmetric limb weakness, fasciculations, atrophy)

and

UMN deficits (pseudobulbar palsy, dysarthria, dysphagia, emotional lability, spastic gait, clonus)

Fatal (COMMONLY KNOWN AS Lou Gehrig Disease)

Question 5

Amyotrophic Lateral Sclerosis Treatment

Answer 5

Riluzole

Question 6

Amyotrophic Lateral Sclerosis

Spinal lesion locations

Answer 6

• UMN Corticobulbar/corticospinal
• LMN (medullary and spinal cord)
• LMN due to anterior horn cell involvement

Question 7

Complete Occlusion of anterior spinal artery Clinical Presentation & Pathophysiology

Answer 7

Spares dorsal columns and Lissauer tract

Mid-thoracic ASA territory is watershed area, as artery of Adamkiewicz supplies ASA below T8

Can be caused by aortic aneurysm repair

Presents with UMN deficit below the lesion (corticospinal tract)

LMN deficit at the level of the lesion (anterior horn),

loss of pain and temperature sensation below the lesion (spinothalamic tract)

Question 8

Complete Occlusion of anterior spinal artery

Spinal lesion location

Answer 8

• UMN deficit below the lesion (corticospinal tract)
• LMN deficit at the level of the lesion (anterior horn)
• loss of pain and temperature sensation below the lesion (Spinothalamic tract)

Question 9

Tabes Dorsalis Clinical Presentation & Pathophysiology

Answer 9

Caused by 3° Syphilis

Results from degeneration (demyelination) of dorsal columns and roots → progressive sensory ataxia (impaired proprioception → poor coordination)

+ Romberg Sign and absent DTRs

Associated with Charcot joints, shooting pain, Argyll Robertson pupils

Question 10

Tabes Dorsalis

Spinal Lesion Location

Answer 10

Degeneration (demyelination) of dorsal columns and roots

Question 11

Syringomyelia Clinical Presentation & Pathophysiology

Answer 11

Syrinx expands and damages anterior white commissure of spinothalamic tract (2nd-order neurons) → bilateral symmetrical loss of pain and temperature sensation cape-like distribution

seen with Chiari I malformation

Can affect other tracts

Question 12

Syringomyelia

Spinal Lesion Location

Answer 12

anterior white commissure of spinothalamic tract (2nd-order neurons)

Question 13

Vitamin B₁₂ Deficiency Clinical Presentation & Pathophysiology

Answer 13

Subacute combined degeneration (SCD) – demyelination of Spinocerebellar tracts, lateral Corticospinal tracts, and Dorsal Columns

Ataxic gait, paresthesia, impaired position/vibration sense

Question 14

Vitamin B₁₂ Deficiency

Spinal Lesion Location

Answer 14

• Spinocerebellar tracts
• Lateral Corticospinal tracts
• Dorsal columns

Question 15

Cauda Equina Syndrome Clinical Presentation & Pathophysiology

Answer 15

Compression of spinal roots L2 and below, often due to intervertebral disc herniation or tumor

Unilateral radicular pain, absent knee, and ankle reflex, loss of bladder and anal sphincter control, saddle anesthesia

Question 16

Cauda Equina Syndrome Treatment

Answer 16

• emergent surgery
• steroids

Question 17

Poliomyelitis Etiology

Answer 17

• Caused by poliovirus (fecal-oral transmission)
• Replicates in oropharynx and small intestine before spreading via bloodstream to CNS
• The infection causes the destruction of cells in the anterior horn of the spinal cord (LMN death)

Question 18

Poliomyelitis Clinical Presentation

Answer 18

Signs of LMN Lesion:

• asymmetric weakness,
• hypotonia
• flaccid paralysis
• fasciculations
• hyporeflexia
• muscle atrophy
• Respiratory muscle involvement leads to respiratory failure

Signs of infection: Malaise, headache, fever, nausea, etc.

Question 19

Poliomyelitis Confirmatory test findings

2 listed

Answer 19

• CSF shows ↑ WBCs (lymphocytic pleocytosis) and slight ↑ of protein (with no change in CSF glucose)
• Virus recovered from stool or throat

Question 20

Brown-Sequard Syndrome Hemisection of spinal cord findings

Answer 20

1. Ipsilateral loss of all sensation at the level of the lesion
2. Ipsilateral LMN signs (e.g. flaccid paralysis) at the level of the lesion
3. Ipsilateral UMN signs below the level of the lesion (due to corticospinal tract damage)
4. Ipsilateral loss of proprioception, vibration, light (2-point discrimination) touch, and tactile sense below the level of lesion (due to dorsal column damage)
5. Contralateral loss of pain, temperature, and crude (nondiscriminative) touch below the level of lesion (due to spinothalamic tract damage)

If the lesion occurs above T1, the patient may present with ipsilateral Horner syndrome due to damage of the oculosympathetic pathway

Question 21

Friedreich Ataxia Etiology

Answer 21

Autosomal recessive trinucleotide repeat disorder (GAA) on chromosome 9 in a gene that encodes frataxin (iron-binding protein)

Leads to impairment in mitochondrial functioning

Question 22

Friedreich Ataxia Pathophysiology & Clinical Presentation

Answer 22

Degeneration of lateral corticospinal tract (spastic paralysis), spinocerebellar tract (ataxia) dorsal columns (↓ vibratory sense, proprioception), and dorsal root ganglia (loss of DTRs)

Staggering gait, frequent falling, nystagmus, dysarthria, pes cavus, hammer toes, diabetes mellitus, hypertrophic cardiomyopathy (cause of death)

Question 23

Friedreich Ataxia Age of onset

Answer 23

Presents in childhood with kyphoscoliosis