Dorsal Sural Sensory Nerve Action Potential: A Study for Reference Values

BACKGROUND Dorsal sural sensory nerve action potential (SNAP) could help diagnose early or subclinical peripheral neuropathy. OBJECTIVES To establish reference data for dorsal sural SNAP amplitude, latency, and velocity in healthy participants. MATERIALS AND METHODS A prospective study was conducted in 45 nerves from healthy participants between 18 and 90 years and stratified into three age groups (a = 18-40 years, b = 41-60 years, and c>60 years). StataCorp 12.2 statistical program was used for all statistical analyses. Mean-2 standard deviation was used to generate reference values for the lower limit of amplitude and velocity in each age group. ANOVA with Bonferroni correction was used for intergroup comparisons of amplitude and velocity. Regression analysis was used to compute an equation for the predicted amplitude with age, height, and weight as the covariates. RESULTS The lower limit for amplitude (uv) in Groups a, b, and c was 2.57, 1.97, and 1.01, respectively. The lower limit for velocity (m/s) was 33.6, 32, and 22.8, respectively. Statistical significance was noted between the amplitudes of participants in Groups b and c (P = 0.039) and a and c (P = 0.001). Similarly, velocity was significantly different between Groups b and c (P = 0.04) and a and c (P = 0.008). Age was the covariate with maximum effect on the dorsal sural amplitude. Gender and side-to-side comparison did not show statistical significance for amplitude and velocity measurements. Linear regression analysis of the transformed amplitude gave the predictive equation as (y) =3.338 + age (-0.0167) + height in meters (-0.209) + weight (0.001). CONCLUSION This study provides reference data for dorsal sural SNAP in Indian population stratified by age.