NCV Flashcards
NCV always involves a _______ response.
stimulated
NCV produces a _______ potential.
composite
NCV can examine ______ & ______ systems.
sensory and motor
can separate the two
NCV can examine nerves in a _______ fashion.
segmental
What is the purpose of NCV?
calculate velocity of AP conduction down nerve axons
How is motor response evaluated?
stimulate surface electrodes over muscle
ORTHODROMIC nerve activation
How is sensory response evaluated?
electrodes placed over finger tips or toes in areas without muscle
ANTIDROMIC nerve activation
describe M wave
composite of ALL axons in the nerve and their contracting muscle fibers
the time from stimulus artifact to beg. of M wave is called
conduction time
the time from stimulation at proximal site to M wave is called
proximal latency
the time from stimulation at distal site to M wave is called
distal latency
What is the formula for NCV?
NCV = conduction distance (m) / conduction time (sec)
conduction time = _____ latency - _____ latency
proximal - distal
Why is most distal aspect of nerve omitted from NCV calculations?
do NOT include MU in rder to omit neurotransmitter loading times
What gives M wave its duration?
not all fibers contract simultaneously
faster MUs contract first, slower second
What causes M wave dispersion?
compressive neuropathy or partially reinnervated muscle
slower conduction, more myelin segments in collaterals, some MUs are not innervated
With full degeneration or lesion, NCV values would approach
zero
With pure myelin disease without axonal involvement could have _______ NCV values with no signs of EMG denervation.
decreased NCV
During regeneration, NCV is slower because:
more myelin segments
What is orthodronic?
stimulus in normal physiological direction (for motor NCV: proximal -> distal)
What is antidromic?
stimulus opposite from normal physiological direction (for sensory NCV: CNS -> distal)
Nerve root evaluation can look at both sensory and motor. What are the two elements used to evaluate?
H Reflex: sensory OR motor (tests ventral and dorsal roots)
F Response: motor (tests ventral root only)
H reflex follows the same pathway as?
monosynaptic stretch reflex
H reflex is only used for the ____ nerve root
S1
F response activates ______ neuron.
alpha motor neuron
If F response is abnormal, the H reflex must be ____.
abnormal
If H reflex is slow and F response is normal, must be _______ impairment.
sensory
If H reflex is slow and F response is slow, must be _______ impairment.
motor
but CANNOT rule of sensory
F response is _____ response.
supramaximal
