Electrodiagnostic Testing Flashcards
what is electrodiagnostic testing used for
to assess function and integrity of the PNS and the musculature it innervates
what is NCV
nerve conduction velocity test
helps diagnose nerve damage or disease
measurement of how well electrical signals (APs) travel up/down peripheral nerves
what is EMG
electromyography
determines myopathic involvement
measurement of how muscles respond to electrical signals (APs) both during rest and with activity
what info does EMG and NCV provide?
time course
anatomic location (sometimes)
nature of pathology
distribution of pathology
physiological status of lesion
data for clinical/lab use
what are the primary components of a NCV?
motor nerve conduction testing
sensory nerve conduction testing
F-wave study
H-reflex study
what nerves do we test in a NCV?
large nerves are easier to zap
what are you looking at in the motor nerve conduction testing for a NCV?
not muscle contraction, the amplitude of the AP before the NMJ
compound motor action potential - CMAP
latency
conduction velocity
what are you looking at in the sensory nerve conduction testing for a NCV?
sensory nerve action potential - SNAP
latency
conduction velocity
what is orthodromic testing
natural direction of sensory APs
NCV
what is antidromic testing
opposite direction of sensory APs
is orthodromic or antidromic testing more common and why?
antidromic
examiner preference
generally easier
what are F-waves in NCV
retograde “rebound” motor impulse
travels full length of motor axon and back
what are F-waves used to evaluate
proximal damage and demyelination
what conditions would you look at F-waves
GBS/CIDP
radiculopathy
peripheral neuropathies
what is H-reflex
used to evaluate radiculopathy
follows muscle stretch reflex arc
when can a H-reflex help
in the evaluation of nerve root lesions, UPPER motor neuron lesions
what is the ampliture related to in a NCV test
of axons in the nerve
what is latency in a NCV
marker of time, therefore most affected by demyelinating processes
what can conduction velocity be affected by
axonal loss and demyelination
what will happen to conduction velocity when large, fast conducting fibers are lost
moderate slowing
what will happen to conduction velocity when demyelination occurs
marked slowing
what is NCV testing easily affected by
easily affected by age, temperature, obestiy, edema
must be diligent about electrode placement
