Orthodromic vs antidromic sensory nerve latencies in healthy persons.

Sensory nerve action potentials may be evoked antidromically (AD) by stimulating a nerve proximally and recording distally, or orthodromically (OD) by stimulating distally and recording over the nerve trunk proximally. The objective of this study was to compare OD and AD distal latencies in healthy subjects. Fifty-two volunteers (average age 30 years) were tested. Orthodromic and AD sensory distal latencies of the median and ulnar nerves of the nondominant hand were obtained. Hand temperature was controlled at 32C. Six subjects were also tested at a hand temperature of 24C. In all subjects tested the OD latency was shorter than the AD latency. Median nerve AD = 3.14 +/- 0.20 (mean latency in ms +/- 1 standard deviation); median nerve OD = 2.94 +/- 0.20; ulnar nerve AD = 3.07 +/- 0.22; ulnar nerve OD = 2.85 +/- 0.19. Mean difference between the latencies obtained (OD vs AD) for the median and ulnar nerves was statistically significant (p less than 0.001). In addition, this difference was over twice as great at 24C compared to 32C for both median and ulnar nerves. Because of the difference between OD and AD sensory latencies, the standard values obtained using one method cannot be rigorously applied when utilizing the other method. Individual laboratories should develop their own normal values for both OD and AD methods, or be specific in performance of the studies when utilizing standards from the literature.