Nomogram for determining the lower normal limits for radial sensory nerve action potentials

Introduction: In this study we aimed to determine the normal lower limits of sensory nerve action potential (SNAP) amplitude of the radial nerve by taking into account age, height, weight, and body mass index (BMI).

Methods: Three hundred thirty-four volunteers, 168 men and 166 women, were recruited. Sensory nerve conduction studies of the radial nerve were performed, and reproducible waveforms were obtained.

Results: The mean radial SNAP amplitude was 44.87 ± 14.58 (range 24-92) μV. SNAP amplitude had a statistically strong negative correlation with age, height, weight, and BMI of the subjects. A multiple linear correlation equation was computed, based on age and BMI of the subjects, to calculate the lower normal limits of radial SNAP and to construct the corresponding nomogram. Conclusion The lower limit of normal SNAP amplitude of the radial nerve, determined in individual subjects using the nomogram, is a useful tool for detection of polyneuropathy.