A New and Noninvasive Antidromic Technique for Electrophysiological Evaluation of the Feet Digital Nerves

The purpose of this study was to introduce a new and noninvasive technique for antidromic electrophysiological evaluation of the feet digital nerves to find normal values of amplitudes and nerve conduction velocity (NCV). Ring electrodes were used to record sensory nerve action potentials from the digits one, two, and three of the foot. The E1 electrode was placed on the proximal phalanx, and the E2 electrode was located 1 cm distal to E1. The nerves were stimulated 10 cm proximal to the E1 electrode on the plantar surface. The 95% confidence intervals (CI) were used to report the normal values of the amplitudes, distal sensory latencies, and nerve conduction velocities. Twenty three healthy volunteers with a mean age of 47.3 ± 8.2 years were recruited in this study. The 95% CI of the sensory amplitudes were 5.2-7.5 μV, 6.0-8.9 μV, and 6.9-10.1 μV for the first, second, and third digits, respectively. There was an inverse relationship between the age and the amplitude (r = -0.48; P = 0.03). The relationship between body mass index (BMI) and amplitude was not significant (r = 0.23; P = 0.41). This new and noninvasive electrodiagnostic technique can be useful in early detection of distal neuropathy of the lower limbs; particularly when the routine electrodiagnostic studies may not be capable of diagnosing the subclinical neuropathy.