Electrodiagnostic Testing

Question 1

what is electrodiagnostic testing used for

Answer 1

to assess function and integrity of the PNS and the musculature it innervates

Question 2

what is NCV

Answer 2

nerve conduction velocity test

helps diagnose nerve damage or disease
measurement of how well electrical signals (APs) travel up/down peripheral nerves

Question 3

what is EMG

Answer 3

electromyography

determines myopathic involvement
measurement of how muscles respond to electrical signals (APs) both during rest and with activity

Question 4

what info does EMG and NCV provide?

Answer 4

time course
anatomic location (sometimes)
nature of pathology
distribution of pathology
physiological status of lesion
data for clinical/lab use

Question 5

what are the primary components of a NCV?

Answer 5

motor nerve conduction testing
sensory nerve conduction testing
F-wave study
H-reflex study

Question 6

what nerves do we test in a NCV?

Answer 6

large nerves are easier to zap

Question 7

what are you looking at in the motor nerve conduction testing for a NCV?

Answer 7

not muscle contraction, the amplitude of the AP before the NMJ

compound motor action potential - CMAP
latency
conduction velocity

Question 8

what are you looking at in the sensory nerve conduction testing for a NCV?

Answer 8

sensory nerve action potential - SNAP
latency
conduction velocity

Question 9

what is orthodromic testing

Answer 9

natural direction of sensory APs
NCV

Question 10

what is antidromic testing

Answer 10

opposite direction of sensory APs

Question 11

is orthodromic or antidromic testing more common and why?

Answer 11

antidromic

examiner preference
generally easier

Question 12

what are F-waves in NCV

Answer 12

retograde “rebound” motor impulse
travels full length of motor axon and back

Question 13

what are F-waves used to evaluate

Answer 13

proximal damage and demyelination

Question 14

what conditions would you look at F-waves

Answer 14

GBS/CIDP
radiculopathy
peripheral neuropathies

Question 15

what is H-reflex

Answer 15

used to evaluate radiculopathy
follows muscle stretch reflex arc

Question 16

when can a H-reflex help

Answer 16

in the evaluation of nerve root lesions, UPPER motor neuron lesions

Question 17

what is the ampliture related to in a NCV test

Answer 17

of axons in the nerve

Question 18

what is latency in a NCV

Answer 18

marker of time, therefore most affected by demyelinating processes

Question 19

what can conduction velocity be affected by

Answer 19

axonal loss and demyelination

Question 20

what will happen to conduction velocity when large, fast conducting fibers are lost

Answer 20

moderate slowing

Question 21

what will happen to conduction velocity when demyelination occurs

Answer 21

marked slowing

Question 22

what is NCV testing easily affected by

Answer 22

easily affected by age, temperature, obestiy, edema
must be diligent about electrode placement