Peripheral Nerves

Question 1

Axonal degeneration is typically “length-dependent” involving the distalmost parts of the largest and longest nerves first except for this condition, which although axonal presents with mainly proximal weakness

Answer 1

Porphyria

Question 2

Denervation atrophy reduces muscle volume by how much? When is it maximal?

Answer 2

Reduces volume by 75-80%

Maximal in 90-120 days (3-4 mos)

Question 3

Disuse atrophy reduces muscle by at most?

Answer 3

25-30%

Question 4

Neuropathies are as a rule associated reduction or loss of tendon reflexes except in this type, even with marked loss of percetion of painful stimuli.

Answer 4

Small-fiber neuropathies

DTRs depend on large heavily myelinated fibers from muscle spindles hence may be retained

Question 5

Antibodies implicated in GBS and associated syndromes

Answer 5

anti-GM1 or anti-GD1a - acute axonal motor
anti-GQ1b - Fisher/ophthalmoplegia
anti-GT1a - phrayngeal-cervical-brachial variant

Question 6

Ability to count to 20 in 1 deep breath corresponds to a vital capacity of

Answer 6

> 1.5L

Question 7

Most important predictors of responsiveness to plasma exchange in GBS

Answer 7

1. younger age

2. Preservation of motor compound muscle action potential amplitudes prior to starting treatment

Question 8

Advised regimen for plasma exchange in GBS

Answer 8

Remove 200-250mL/kg of plasma in 4-6 treatments on alternate days
Replace fluid with saline + 5% albumin

Question 9

Triad most characteristic of Lyme disease during its disseminated phase (1-3wks after bite or appearance of typical rash)

Answer 9

Cranial nerve palsies
Radiculitis
Aseptic Meningitis

Question 10

Pathology of DM neuropathy

Answer 10

Loss of myelinated fibers
+ segmental demyelination and remyelination of remaining axons
Onion bulb formations of schwann cells and fibroblasts

Unmyelinated fibers also reduced in number

Basement membrane of intraneural capillaries thickened and duplicated