PNS and Skeletal Muscle Pathology (Martin)

Question 1

When are myelin ovoids seen?

Answer 1

in axonal degeneration and muscle fiber atrophy; Schwann cells catabolize myelin and later engulf axon fragments, producing small oval compartments

Question 2

What happens to the muscle fiber during axonal degeneration?

Answer 2

denervation atrophy; the muscle fiber undergoes atrophy and produces angulated fibers (triangular shaped)

Question 3

What do you see?

Answer 3

angulated atrophic fibers (triangular shaped) seen in axonal degeneration

Question 4

What happens to the nuclei during muscle fiber regeneration?

Answer 4

nuclei are not facing the periphery (normal); they are centrally located

Question 5

Answer 5

muscle fiber regeneration; nuclei are not facing the periphery (normal); they are centrally located

Question 6

thin unmyelinated fibers

Answer 6

pain and temperature; slowest conduction speeds due to lack of myelin and small diameter

Question 7

large diameter axons with thick myelin sheaths

Answer 7

light touch and motor signals; fast conduction speeds due to myelin and larger diameter

Question 8

Electrophysiologic hallmark of axonal neuropathies

Answer 8

a reduction in signal amplitude with preservation of conduction velocity

Question 9

Electrophysiologic hallmark of demyelinating neuropathies

Answer 9

slowed nerve conduction velocity

Question 10

Bell’s palsy

Answer 10

unknown cause injury to CN VII that causes facial muscle paralysis; one sided facial droop; associated with URI and DM

Question 11

Guillain Barre Syndrome (GBS)

Answer 11

autoimmune demyelinating polyneuropathy (anti-myelin abs); ascending paralysis beginning in the distal limbs and rapidly advancing to the proximal limbs; DTRs disappear; preceded by acute influenza-like illness (campylobacter jejuni, EBV and mycoplasma pneumonia or prior vaccinations)

Question 12

Guillain Barre Syndrome (GBS) is typically seen preceding which illness with what organisms?

Answer 12

campylobacter jejuni, EBV and mycoplasma pneumonia or prior vaccinations

Question 13

CSF in Guillain Barre Syndrome (GBS)

Answer 13

increased protein in the CSF

Question 14

Treatment of Guillain Barre Syndrome (GBS)

Answer 14

plasmapheresis and IVIg (rid of anti-myelin abs)

Question 15

What is the most common acquired inflammatory peripheral neuropathy?

Answer 15

chronic inflammatory demyelinating polyneuropathy (CIDP); symmetrical mixed sensorimotor polyneuropathy that persist for > 2months with relapses and remissions; will see onion bulbs on histo

Question 16

Answer 16

onion bulbs seen in chronic inflammatory demyelinating polyneuropathy (CIDP)

Question 17

What is the organism that causes lepromatous leprosy?

Answer 17

mycobacterium leprae

Question 18

Lepromatous leprosy

Answer 18

Schwann cells are invaded by mycobacterium leprae and causes segmental demyelination and re-myelination; will see endometrial fibrosis on histo with multilayered thickening of perineurial sheaths affects cool extremities; involves pain fibers; loss of sensation contributes to injury

Question 19

Diphtheria

Answer 19

Diphtheria exotoxin produced by corynebacterium diphtheria; beings as paresthesias and weakness with loss of proprioception and vibration sensation; can cause prominent bulbar and respiratory muscle dysfunction leading to death or long term disability

Question 20

Myasthenia Gravis

Answer 20

occurs in young females and older men; loss of acetylcholine receptors due to autoantibodies to AChR; presents with fluctuating weakness that worsens with exertion; EMG shows diminished response after repeated stimulation; involves extra-ocular muscles (diplopia and ptosis) and treated with acetylcholinesterase inhibitors

Question 21

Lambert-Eaton Myasthenia Syndrome (LEMS)

Answer 21

antibodies block the release of ACh on presynaptic membrane associated with small cell carcinoma of the lung; repetitive stimulation increases muscle response

Question 22

What are the 3 types of non-infectious inflammatory myopathies?

Answer 22

1. Dermatomyositis
2. Polymyositis
3. Inclusion Body myositis

Question 23

Dermatomyositis

Answer 23

non-infectious inflammatory myopathy; affects skin AND skeletal muscle; histological hallmark of perifasciclar atrophy; lilac or heliotrope discoloration of eyelids; presents with difficulty rising from chair or climbing stairs

autoantibodies:
1. anti-Mi2
2. anti-Jo1
3. anti-P155/P140

Question 24

What is the hallmark on biopsy in a patient with Dermatomyositis?

Answer 24

perifasciclar atrophy

Question 25

What are the antibodies that are associated with Dermatomyositis?

Answer 25

autoantibodies:
1. anti-Mi2 (heliotrope rash)
2. anti-Jo1 (interstitial lung disease)
3. anti-P155/P140 (paraneoplastic cases)

Question 26

Answer 26

A. lilac or heliotrope discoloration of eyelids
B. perifasciclar atrophy

both seen in Dermatomyositis; non-infectious inflammatory myopathy; affects skin AND skeletal muscle