Median nerve determinations: analysis of two techniques

The objective of this study was to compare two techniques of obtaining median motor and sensory nerve determinants. One method utilized premeasured electrode placement, while the other used anatomic landmarks. It was postulated that increased accuracy could be achieved by more precise measuring techniques. The right median nerve in 50 able-bodied subjects was investigated. Each subject was tested by both anatomic and premeasured methods. Skin temperatures were maintained between 31C and 33C. Latencies were measured to onset and peak, and amplitudes were gauged from baseline to peak. Latency studies were evaluated. Results concluded that mean distal motor latencies, stimulating 8cm from active recording electrode, was 3.1msec +/- 0.4 and amplitude was 11.1mV +/- 3.0. Stimulating at distal wrist crease, mean latency was 2.6msec +/- 0.38 and amplitude was 11.3mV +/- 3.6. Sensory latencies to onset of response when stimulating 14cm from active ring electrode with reference 4cm distally were 2.1msec +/- 0.25. Sensory latency when stimulating at wrist crease and ring electrodes over proximal interphalangeal and distal interphalangeal joints was 2.1msec +/- 0.25 to onset and 2.8msec +/- 0.32 to peak and amplitude was 36.1 +/- 14.6. The authors concluded that there was no statistically significant difference in accuracy between the premeasured and anatomic methods.