Peripheral Nerve Pathology Flashcards
what is a motor unit and what is it composed of
functional unit of neuromusclar system
- lower motor neurons, axon, muscle fibers
nerve fiber? composed of
structural component of peripheral nerve
- axon, schwann cell, and myelins sheath
what do axons contain
organelles
what does not occur in the axons? where does it occur
no protein synthesis
- delivered from perikaryon
internodes
mylinated segments
one schwann cell per internode
what are internodes separated by
nodes of ranvier
endoneruium
surrounds individual nerve fibers
perineurium
encloses each fascicle
epineurium
encloses entire nerve
what happens in remyelination in segmental demylination
new internodes are shorter
new myelin sheath is thinner
what does segmental demyelination look like under the microscope
onion ring
how does axonal degeneration occur
injury due to a focal lesion results in wallerian degeneration distal to lesion
what happens to muscle fibers in affected motor unit that has axonal degeneration
denervation atrophy
what happens in nerve regeneration
-proximal stumps of degenerated axons sprout and elongate, develop new growth cones
- growth cones guided by Schwann cells
-
what is the histological evidence of nerve regeneration
regenerating cluster: multiple closely aggregated thinly myelinated small-caliber axons
name an immune-mediated Neuropathy disease
Guillian-Barre Neuropathies
how is Guillian-Barre characterized clinically. how threatening is this disease
weakness beginning with distal muscles rapidly progressing to proximal muscles
- life threatneing
- loss of deep tendon reflex
- nerve velocity slowed
2/3 of Guillian-barre cases are preceded by what
acute influenza
or pt has recovered before onset of neuropathy
what is the morphology of Guillian-Barre
inflammation of peripheral nerve
segmental demyelination
remyelination
what are CSF values for Guillian-Barre
elevated protein CSF
name an infectious polyneuropathies
leprosy
mycobacterium leprae invade what cells in the nervous system
schwann cells
varicella-Zoster ( shingles)
how does polyneuropathy occur in lepromatous leprosy
symmetric poluneuropathy
involves pain fibers
loss of sensation leading to injuries and large traumatic ulcers on extremities
what are the two types of leropsy
lepromatous
tuberculoid
what is a difference in clinical presentation in lepromatous and tuberculoid leprosy
more localized nerve involvement in tuberculoid leprosy
what is the MOA for tuberculoid leprosy
- cell-mediated immune response by nodular granulomaotus inflammation in dermis
- schweann cells, loose myelin b/c they were in the vicinity
what is the morphology for varicella-Zoster
neuronal destruction and loss
- mononuclear inflammatory infiltrates
- regional necrosis with hemorrhage
- axonal destruction after death of sensory nerves
what does the histology of Varicella-zoster look like
intranucluar inclusions seen in satellite cells around ganglion cells in dorsal root ganglion
what is the morphology for peripheral neuropathy in adult-onset diabetes mielitis
axonal neuropathy
segmental demyelination
endoneruial arteries with thickening and hyalinization
what is the clinical course of peripheral neuropathy in adult-onset DM
symmetric neuropathy most common
sensation in distal extremities
motor abnormalities less evident
ulcers that heal poorly
Name traumatic neuropathies of peripheral nerve
transection
compressed neuropathy
how does transection try to fix itself
regeneration is difficult because discontinuity between proximal and distal portions of nerve sheath
- axons grow and make a mass of tanlged axons called traumatic neuroma
describe traumatic neuroma
small bundles of axons appear randomly oriented but are surrounded by organized layers of Schwann cells
what syndrome is associated with compression neuropathy
carpal tunnel syndrome
explain carpal tunnel syndrome
compression of median nerve by transverse carpal ligament
Name a hereditary neuropathy
hereditary motor and sensory neuropathies HMSN
HMS present as spectrum of disorders all caused by mutations in genes involved in
formation and maintenance of myelin
what are the 2 types of HMSN diseases
I: Charcot-Marie-tooth-Disease
I: CMT disease
clinical presentation for I: Charcot-Marie-tooth-Disease
may be asymptomatic
- distal muscle weakness
- atrophy of calf muscle
- orthopedic problems of foot
what chromosomes are involved in HMSN I CMT disease
17p11.2
1
16
what is the morphology for CMT disease
demyelinating neuropathy
“onion bubs”
hypertrophic neuropathy: palpable
what is the clinical course for CMT diseae
slowly progressive
normal lifespan
disability of sensorimotor deficits
