The effect of temporal dispersion on compound action potential area in human peripheral nerve.

In 32 ulnar nerves of healthy volunteers, the mean area of the compound muscle action potential recorded over abductor digiti minimi was reduced by 7.4% when comparing above-elbow with wrist stimulation and by 1.9% when comparing above-elbow with below-elbow stimulation. In 20 of these nerves, the mean area of the compound nerve action potential (CNAP) recorded over the fifth digit was reduced by 36% when comparing above-elbow with wrist stimulation. Area reduction of the compound action potential, especially of the CNAP, appears to be a characteristic effect of temporal dispersion in peripheral nerve when utilizing the bipolar recording technique routinely employed in clinical neurophysiology. A thorough understanding of the effects caused by temporal dispersion and of their quantitative limits in normal peripheral nerve is important for the proper interpretation of nerve conduction studies.