PNS and Skeletal Muscle Pathology (Martin) Flashcards
When are myelin ovoids seen?
in axonal degeneration and muscle fiber atrophy; Schwann cells catabolize myelin and later engulf axon fragments, producing small oval compartments
What happens to the muscle fiber during axonal degeneration?
denervation atrophy; the muscle fiber undergoes atrophy and produces angulated fibers (triangular shaped)
What do you see?
angulated atrophic fibers (triangular shaped) seen in axonal degeneration
What happens to the nuclei during muscle fiber regeneration?
nuclei are not facing the periphery (normal); they are centrally located
muscle fiber regeneration; nuclei are not facing the periphery (normal); they are centrally located
thin unmyelinated fibers
pain and temperature; slowest conduction speeds due to lack of myelin and small diameter
large diameter axons with thick myelin sheaths
light touch and motor signals; fast conduction speeds due to myelin and larger diameter
Electrophysiologic hallmark of axonal neuropathies
a reduction in signal amplitude with preservation of conduction velocity
Electrophysiologic hallmark of demyelinating neuropathies
slowed nerve conduction velocity
Bell’s palsy
unknown cause injury to CN VII that causes facial muscle paralysis; one sided facial droop; associated with URI and DM
Guillain Barre Syndrome (GBS)
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)
Guillain Barre Syndrome (GBS) is typically seen preceding which illness with what organisms?
campylobacter jejuni, EBV and mycoplasma pneumonia or prior vaccinations
CSF in Guillain Barre Syndrome (GBS)
increased protein in the CSF
Treatment of Guillain Barre Syndrome (GBS)
plasmapheresis and IVIg (rid of anti-myelin abs)
What is the most common acquired inflammatory peripheral neuropathy?
chronic inflammatory demyelinating polyneuropathy (CIDP); symmetrical mixed sensorimotor polyneuropathy that persist for > 2months with relapses and remissions; will see onion bulbs on histo
onion bulbs seen in chronic inflammatory demyelinating polyneuropathy (CIDP)
What is the organism that causes lepromatous leprosy?
mycobacterium leprae
Lepromatous leprosy
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
Diphtheria
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
Myasthenia Gravis
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
Lambert-Eaton Myasthenia Syndrome (LEMS)
antibodies block the release of ACh on presynaptic membrane associated with small cell carcinoma of the lung; repetitive stimulation increases muscle response
What are the 3 types of non-infectious inflammatory myopathies?
- Dermatomyositis
- Polymyositis
- Inclusion Body myositis
Dermatomyositis
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
What is the hallmark on biopsy in a patient with Dermatomyositis?
perifasciclar atrophy
What are the antibodies that are associated with Dermatomyositis?
autoantibodies:
1. anti-Mi2 (heliotrope rash)
2. anti-Jo1 (interstitial lung disease)
3. anti-P155/P140 (paraneoplastic cases)
A. lilac or heliotrope discoloration of eyelids
B. perifasciclar atrophy
both seen in Dermatomyositis; non-infectious inflammatory myopathy; affects skin AND skeletal muscle
