Nerve conduction velocities

Nerve conduction velocities (NCV):
Sensitive indicators of nerve function – can be performed on sensory, motor or mixed nerves. Nerve is stimulated and the resulting waveform or evoked potential is recorded from nerve or muscle.

Tests only the fastest myelinated fibres (unmyelinated c fibres can not be assessed with NCV).

Contraindicated in those with a pacemaker.

Electrode applied on skin over nerve to depolarise it  response is measured in muscle (motor nerves) or nerve (sensory nerves).
3 parameters are measured:
1) Distal latency (time between the stimulus and onset of a response)
2) Amplitude (height of evoked potential or waveform)
3) Conduction velocity

• provides information on the S1 afferent-efferent reflex arc

• the delayed motor potential following a normal MUAP
• represents the antidromic response seen when the motor nerve is stimulated
• important screening test for Guillain Barre syndrome

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