Changes in duration and amplitude of the evoked muscle action potential (EMAP) over distance in peroneal, median, and ulnar nerves.

Standard nerve conduction techniques measure the conduction of the fastest conducting axons. Slower conducting axons determine the amplitude, duration, and configuration of the EMAP. Normal data showing the change in amplitude and duration of the evoked EMAP over a length of nerve segment as well as the change per centimeter of that nerve segment has been lacking. This study supplies this data for the peroneal, median and ulnar nerves (tables 2-5) and gives examples of clinical application of these techniques in the diagnosis of compression syndrome and peripheral neuropathies with demyelination. Emphasis is also placed on potential sources of error which may affect the results obtained using these techniques. Further study of the application of these techniques in the diagnosis of neuropathies is indicated.