Measurement of nerve conduction--a comparison of orthodromic and antidromic methods.

The validity of the antidromic method in the measurement of median and ulnar sensory nerve conduction is determined. Analysis of our results show that both the orthodromic and antidromic methods provide consistent results. Both methods were accurate in diagnosing Carpal Tunnel Syndrome (CTS), with an upper limit of normal for distal sensory latency of 4.5 msecs motor, and 4.0 msecs sensory in the median nerve. Variation with age and sex was studied. Latency when measured by either method showed no variation. Amplitude showed a consistent decrease with age. No sex difference was detected. We conclude that the antidromic stimulatory method is accurate, reproducible, and convenient, and therefore is at least as good if not better than the orthodromic method in the context of a busy routine electrodiagnostic clinic.