Neuropathy, Myopathy, & Motor Neuron Dz Flashcards
single major named nerve has deficits due to trauma/compression
mononeuropathy
localization of mononeuropathy via
EMG
disorder of multiple nerves, sxs often symmetrical, sensation affected early, dec reflexes early on
polyneuropathy or peripheral neuropathy
why are distal regions affected first for peripheral neuropathy
longest nerves affected first b/c metabolic maintenance and axoplasmic flow are more susceptible to neurotoxic factors
spontaneous tingling
“pins and needles”
paresthesia
unpleasant sensation from non-noxious stimuli
dysesthesia
sxs of polyneuropathy or peripheral neuropathy
sxs often symmetrical, sensation affected early, dec reflexes early on, weakness/sensation affected distally first
2 pathological processes in neuropathy
demyelination
axonal degeneration
mononeuropathy from focal compression due to
demyelination
ex: carpal tunnel
(axonal degen is secondary process)
2 ex of demyelination
guillan barre (polyneuropathy) carpal tunnel (mononeuropathy)
mechanism of axonal loss
Wallerian degen - axons and myelin degenerate distal to where nerve was injured
support scaffolding that guides regrowing of axons
perineurium
lack of perineurium leads to
resprouting axons piling up in a bulbous neuroma (often painful)
primary pathology for polyneuropathies due to toximetabolic cause
axonal degen (demyelination is secondary process)
nerve at wrist, elbow, and fibular head
wrist - median n
elbow - ulnar n
fibular head - common peroneal n
tests electrical activity and function of nerves and muscles
EMG
if EMG suggests chronic polyneuropathy due to inflamm, immune, or vasculitis - confirm dx via
sural (sensory n) biopsy
biopsy of sural nerve results in
permanent numbness along lateral foot
treatable causes of polyneuropathy - screen for
DM liver/kidney probs Vit B12 deficiency hypothyroidism anemia/leukemia (CBC)
MOA of topical capsaicin
substance P depleter
oral meds for neuropathic pain
anticonvulsants (gabapentin, pregabalin, carbamazepine) or antidepressants (amitriptyline or duloxetine)
immune system targets peripheral nerve myelin and gives ascending, areflexic paralysis
guillan barre (after viral illness, surgery, or trauma)
guillan barre weakness plateaus when
after 3-4 wks
guillan barre EMG
shows asymmetrical demyelination in proximal and distal segments of diff nerves
guillan barre CSF
may have elevated protein, few wbcs (if any), no signs of infection
faster recovery for guillan barre if you administer
plasmapheresis (removes circulating ab) or IVIG (gives ab that counteract the autoimmune process)
myopathy sxs
proximal weakness, nl sensation, late loss of reflexes (after atrophy)
rapid weakness from viral induced breakdown of musc fibers seen with
influenza
meds that can give weakness
statins
corticosteroids
endocrine dz that can give myopathy
cushing’s
hypothyroid
dx of myopathy
measure creatine kinase (CK)
EMG
muscle biopsy
inflammation of multiple muscles, typically autoimmune in US
polymyositis
myositis w/ periorbital and knuckle rash
dermatomyositis
muscle biopsy of myositis
inflamm cell infiltrates admist necrotic and regenerating musc fibers
hereditary myopathies of variable progression/severity
musc dystrophies
death for duchenne’s caused by
weak respiratory musc or cardiomyopathy
excessive trinuc repeats on chromosome 19 giving abnl protein kinase
myotonic dystrophy type 1, autosomal dominant
sxs of myotonic dystrophy
weakness of distal limbs, neck, and face, weak jaw closure (often hangs open)
impaired relaxation of muscle after volitional contraction
myotonia
exam step to elicit myotonia
percussion of thenar musc w/ reflex hammer
other sxs of myotonic dystrophy not neuro related
cataracts, frontal baldness, infertility, cardiac arrhythmias
tracts for UMN
CST - anterior horn cells
corticobulbar tract - CN (LMNs)
dz that only involves anterior horn cells, often hereditary
SMA
SMA sxs
LMN signs - weakness, atrophy, fasciculations, hyporeflexia
infantile onset SMA
Werdnig Hoffman
slowly progressive atrophy of one limb or restricted segments of limbs, normal lifespan
benign focal amyotrophy
familial degen of CST in lateral columns of spinal cord not due to structural/metabolic issues
primary lateral sclerosis (weakness + UMN signs)
dz where only corticobulbar tract is involved
psuedobulbar palsy (facial weakness, dysphagia, hoarseness, impaired chewing, dysarthria) w/ inc jaw jerk
cause of pseudobulbar palsy
MS lesions, trauma, tumors, b/l mutl cerebral infarcts
focal weakness/atrophy in limb (“drop”) that spreads and becomes b/l, male 40-70 y/o
ALS
ALS that starts w/ dysarthria, hoarseness, or impaired swallowing
bulbar ALS
sxs of ALS
widespread fasciculations, spasticity, hyper-reflexia, atrophy, weakness
spared w/ ALS
extraocular musc
bladder/bowel fxn
familial ALS cause
defective superoxide dismutase…free radicals destroy motor neurons
tx for ALS
no cure, riluzole helps
riluzole MOA
opposes excitotoxic effect of glutamate at NMDA receptors
