Clinical neurphysiology Flashcards
what part of nervous system does NCS and EMG test?
PNS only!
what are 5 uses of NCS
- localize lesion - anterior horn, DRG, nerve root, plexus, peripheral nerve, NMJ, muscle
- Characterize underlying pathology (myelin vs. axonal loss)
- Assess severity and prognosis
- Assess age of lesion
- Determine underlying basis of weakness (neurogenic vs. myogenic)
what part of PNS does NCs assess
large myelnated fibers - not small pain fibers
what are three things measured
- velocity (latency)
- size of response (amplitude)
- change in waveform (conduction block) - motor onlt
what type of stimulus is required
supramaximal
what does amplitude measure
the number of axons being activated by stim
why are 2 points needed
to measure diff.s in latency
what does sensor go for sense studies
somewhere with no motor - fingertips
what is seen with demylenation in motor EMG (3)
- prolongation of distal latenrcy
- slowing of conduction velocity
- conduction block
what does lowered amp. tell us
loss of axon recruitment
3 types of peripheral nerve damage
- focal demylenation
- nerve crush
- nerve laceration
what will happen in EMG in conduction block (demylenation)
normal amplitude distal to lesion, loss of amplitude proximal to lesion
what will happen in EMG in axonal loss
loss in amplitude both distal and proximal to block
what is recovery from demyelnation and axonal loss
- demyelenation - full recovery in month
2. axonal - can be very long and may be incomplete
what is potential pitfall in EMG
if subacute (under 7 days) there still may be some conduciton distal to lesion
