Neuromuscular III (Spinal cord and motor neurons)

Question 1

Mechanism of action of riluzole in ALS

Answer 1

Likely inhibits glutamate excitotoxicity via multiple mechanisms (reduce glutamate release, block Na channels, inhibit NMDAR)

Question 2

UMN variant of motor neuron disease

LMN variant

Answer 2

UMN: Primary lateral sclerosis (PLS)

LMN: Progressive muscular atrophy (PMA) (Also flail arm, flail leg, and genetic MND

Question 3

Cause of tropical spastic paraparesis

Answer 3

HTLV-1 infection

Question 4

Most common cause of spastic paraparesis in an AIDS patient

Answer 4

HIV-related vacuolar myelopathy

Question 5

Most common genetic cause of hereditary spastic paraplegia

Answer 5

SPAST gene for spastin protein, AD inheritance

(Many other causes, including atlastin, araplegin, spartin, and maspardin)

Question 6

Area of spinal cord most susceptible to watershed infarct

Answer 6

Upper-mid thoracic (T4-T8) - watershed territory between vertebral and aortic circulation

Question 7

Part of spinal cord supplied by artery of Adamkiewicz

Answer 7

Lower thoracic to upper lumbar

Question 8

Most common cause of familial ALS

Answer 8

Copper/zinc superoxide dismutase (SOD1) mutations (about 20% of familial ALS)

Question 9

What supplement can cause copper deficiency myelopathy

Answer 9

High-dose zinc supplementation (can lead to copper deficiency)

(High dose zinc induces intestinal metallothionein production, which reduces absorption of copper, zinc, and other heavy metals)

Question 10

Zoonotic illness that can lead to polio-like flaccic paralysis, as well as meningitis, encephalitis, and other manifestations

Answer 10

WNV (a flavivirus)

Question 11

Progressive spastic paraparesis, sensory neuropathy, and adrenal insufficiency

Genetic cause?

Answer 11

Adrenomyeloneuropathy (AMN), a form of X-linked adrenoleukodystrophy (ALD)

X-linked, mutation in ABCD1 gene leading to VLCA accumulation

(Other forms of ALD include childhood cerebral ALD, adult cerebral ALD, and addison’s-only ALD)

Question 12

Most common intradural, extramedullary spinal cord tumor

Answer 12

Meningioma (others include nerve sheath tumors - schwannomas and neurofibromas)

Question 13

Most common intermedullary spinal cord tumors in children and adults

Answer 13

Children: Astrocytomas (usually low-grade)

Adults: Ependymomas

Question 14

Tumor that arises from ependymal cells in the flilum terminale

Answer 14

Myxopapillary ependymoma

Question 15

Superficial siderosis:

Common presentation?

Cause?

LP and MRI findings?

Answer 15

Gait ataxia and SNHL, can also have anosmia, cognitive decline, and myelopathy.

Due to recurrent bleeding into the subarachnoid space (source variable and often not identified)

LP: often xanthochromia and/or RBCs

MRI: T2 hypointensity around brain, brainstem, and spinal cord

Question 16

Trace element deficiency that can mimic B12 deficiency myelopaty

Answer 16

Copper deficiency (can also lead to peripheral neuropathy, optic neuropathy, and CNS manifestations)

Question 17

Syndrome of progressive weakness, proximal-> distal+bulbar a/w LMN signs and gynecomastia, presenting in 30s.

Genetic cause

Answer 17

X-linked spinpbulba musculr atrophy a.k.a. Kennedy’s disease

Trinucleotide CAG repeat in androgen receptor gene on X-chromosome

Question 18

How do SMAs 1-4 vary in age of onset and severity

Answer 18

The higher the number, the later onset and less severe
SMA1: infantile SMA, death by 2 years
SMA2: intermediate SMA, onset 1-2 years, usually contractures and non-ambulatory
SMA3: juvenile SMA, onset 5-15 years, difficulty walking but ambulatory into adulthood
SMA4: adult-onset SMA, onset 20s-30s, usually ambulatory into late adulthood

Question 19

Muscle biopsy finding in SMA

Answer 19

Atrophy of whole fascicles or groups of fascicles with neighboring normal or hypertrophied fascicles

Question 20

Progressive asymmetric wasting of one or less commonly both hands and forearms with atrophy and fasciculations and preserved sensation, and then stabilization

Answer 20

Monomelic amyotrophy a.k.a. Hirayama disease