Evaluation of Nerve Injuries by Evoked Potentials and Electromyography

Abstract

XONS must not only reach muscle but reinnervate it before current clinical methods of measuring peripheral nerve regeneration become useful. Thus there is a delay between the appearance of axons in muscle and measurable function of that muscle. The electromyogram (EMG) may provide earlier evidence that motor fibers of regenerating neuron have reached muscle. A decrease in the number of fibrillations and denervation potentials, and the appearance of nascent motor units, herald the onset of clinical function. ~ Recent evidence suggests that in vivo evoked nerve action potentials (NAP) can be used to evaluate early axon regeneration through an injury.4 Ability to record NAP's depends on the presence of some moderate- or large-sized axons and provides a certain insight as to axon population at the recording site. The purpose of these studies was to compare evoked NAP's recorded from the distal stump of injured but regenerating nerves with EMG information recorded from musculature innervated by the injured nerve. Method Twelve Macaca mulatta monkeys of both sexes were inspected to insure normal function and muscle bulk in the lower extremities. The animals were anesthetized with intravenous phenobarbital. The resting activity of the proximal and distal lower extremity musculature was recorded by concentric needle electrodes. Either the tibial or peroneal nerves in both lower extremities were exposed from their sciatic nerve origin to the point where the nerve entered the proximal lower extremity musculature. The nerve was suspended on bipolar platinum electrodes proximally and distally and on a ground electrode between the proximal stimulating