Neurografi Flashcards
CMAP
Compound Muscle Action Potential - due to muscle fiber depolarization, reflects health of nerve, NMJ and muscle.
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SNAP
Sensory Nerve Action Potential - compared to normal value
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EMG
Measures everything between anterior horn cell to muscle. Often means Nerve conduction and Needle Electrode Examination
Distal latency
From most distal point to skin or muscle, for ex CTS: prolonged distal latency over median nerve
Conduction velocity
Normal 40-50m/s
Ex demyelinating disease Charcot Marie Tooth 4m/s
Axonal polyneuropathy
CMAP and SNAPS reduce. Severe - no response at al
Radikulopathy
CMAP lowered due to Walölerian degeneration
Sens nerve oftan prox to dorsal root ganglion - due to this SNAP is not affected
Plexopathy
CMAP + SNAPS reduced due to injury distal to dorsal root ganglion
Conduction block
CMAP drop over that segment. Start measuring more distally - normal. Than moving prox block over that segment
Repetitive nerve stimulation (RNS)
CMAP decreases as Acetylcholine levels drop in Myastenia Gravis (neuromuscular disease)
Needle Electrode Examination (often part of EMG)
Needle in muscle - listen to fibrillations and fasciculations. MUPS (motor unit potential)
Fibrillation
Muscle fiber that has lost its nerve fiber contact and is dying - sending out this special nerve signal
BAD - reflects active neurogenic process
Can be of any reason in the nerve
Fasciculation
U can see this in the muscle with your own eye also (in normal conditions als=) - classic in anterior horn cell disease
MUP
Muscle Unit Potential
Measures amount of nerve fibers rein nervation - when nerve fiber sprouts to take over damaged nerve fibers the MUPs become larger
Small MUPs in muscle disease (knock out muscle fibers randomly so units become smaller)
