Peripheral N & Skeletal M Path Flashcards
(43 cards)
Segmental demyelination process
Schwann cell dysfunction leads to damage of the myelin sheath. Random internodes of myelin are injured (denuded axon) and remyelinated by multiple Schwann cells while the axon and myocytes remain intact. (Ex. Guillain-Barre Syn)
How can you tell internodes are newly myelinated?
They are shorter than normal and take several to bridge the demyelinated region
What is axon damage?
Axon damage affects whole neuron body or axon
What is a focal lesion
traumatic transection of an axon, the distal portion undergoes Wallerian degeneration
What are myelin ovoids?
Schwann cells that catabolize myelin & later engulf axon fragments producing small oval compartments
If you see triangular ‘angulated’ muscle fibers what process has happened?
Denervation atropy
Axonal degeneration -> muscle fibers in motor unit lose neural input -> DA
What determines muscle fiber type?
Motor neuron determines fiber type
Type 1 v Type 2 neurons. (more for boards)
1 - Sustained force, weight bearing, red, slow-twitch. Lots of lipids with low glycogen
2 - sudden movements, purposeful motion, white, fast-twitch. Lots of glycogen with low lipids
What would cause group atrophy of type 2 fibers?
Inactivity or disuse (limb fracture, pyramidal tract degeneration, neurodegenerative dz)
Glucocorticoid therapy -> steroid myopathy
What are the pathologic reactions of myoctes? (4)
Segmental necrosis - loss of muscle fiber -> deposition of collagen and fat (Ex. Duchenne’s muscular dystrophy)
Hypertrophy - muscle fiber splitting; response to increase load
Regeneration - large internalized nuclei with prominent red RNA under trichrome stain
Vacuolization
Describe the findings of peripheral neuropathy?
Tingling, stabbing, burning or “pins and needles”
Difference between mononeuropathies and polyneuropathies?
Mono - involve a single nerve & deficits are restricted to region
Poly - multiple nerves are involved, usually symmetrically. Deficits ascend with dz progression (stocking & glove distribution)
What is Mononeuritis multiplex and the associated dz’s?
Several nerves damaged in haphazard fashion.
Assoc. with vasculitis like polyarteritis nodosum (PAN)
Ex. HIV
What is affected in polyradiculoneuropathies?
Nerve roots and peripheral nerves
Bell’s Palsy
Mononeruopathy of CN VII
Asymmetrical facial drop assoc. with URI & DM. Usually resolves spontaneously
What is Neurogenic bladder and the dz’s assoc. with it?
Lack of bladder control due to brain, spinal cord or nerve problem.
Assoc. with MS, Parkinson’s, DM, infections, or spina bifida.
Issue with nerves to bladder can cause overactive or underactive bladder
Guillain-Barre
Acute inflammatory immune-mediated demyelinating polyneuropathy.
Anti-myelin abs are produced.
Segmental demyelination with perivenular and endoneurial infiltration.
Weakness begins in distal limbs with ascending paralysis. DTR’s disappear.
Incr. CSF production. Tx with plasmaphreresis or IVIg
Chronic Inflammatory Demyelinating Poly(radiculo)neropathy
Most common aquired inflammatory peripheral neuropathy. Symmetrical and >2mo. Responds to steroids unlike GB! Sural nerve bx shows ONION BULBS
Leprosy (Hansen dz)
Mycobacterium leprae cause segmental demyelination and loss of BOTH myelinated and unmyelinated axons. Endoneurial fibrosis and multilayered thickening of perineural sheaths occurs.
Symmetric polyneuropathy affects cool extremities. Pain fiber involvement & loss of sensation contribute to injuries. AFB (+)
TB Leprosy
Granulomatous nodules in dermis. localized to nerve involvement. AFB (+)
Diptheria
Exotoxin affects peripheral nerves beginning with paresthesias and weakness. Loss of proprioception and vibratory sensation early.
VZV
Most common viral infection of PNS. Ascends to CNS via sensory ganglia. Reactivation of the virus = Shingles.
Loss of affected ganglia, necrosis & hemorrhage can be seen. Axonal degen. of PN after death of sensory neurons. Focal destruction of large motor neurons in anterior horns or CN motor nuclei.
Peripheral neuropathy in DM
Most common cause of peripheral neuropathy, ascending distal symmetric sensorimotor polyneuropathy.
Sx: Numbness, loss of pain sensation, difficulty balancing. Paresthesias & dysesthesias. Diffuse vascular injury
Endoneurial arterioles show thickening, hylinization & intense PAS (+)
Thyroid dysfunction
hypothyroidism -> compression mononeuropathies.
