Ulnar Motor Nerve Conduction Studies: Reference Values and Effect of Age, Gender and Anthropometric Factors

Abstract

Introduction: The aim of the present study is to report normal reference values of nerve conduction studies (NCS) parameters for ulnar motor nerve, and investigate the effect of age, gender and anthropometrical factors height and body mass index (BMI) in the measures. Methods: Ulnar motor NCS were performed on 25 healthy volunteers aged 25.9 ± 4.2 years (mean ± SD), with exclusion criteria related to risk factors for neuropathies. The ulnar nerve was stimulated at the wrist (distal) and below the elbow (proximal); compound muscle action potential (CMAP) was recorded from the abductor digiti minimi. Reference data was estimated as a range of mean ± 2 SD and a range based on the 5th and 95th percentiles. The effect of covariates was evaluated with correlation coefficients and linear regression analysis. Gender comparisons were analyzed with unpaired t-test. Results and Discussion: At distal point the overall results were: amplitude of 9.1 ± 1.4 mV, latency of 2.4 ± 0.3 ms, CMAP duration of 6.4 ± 1.0 ms and area of 27.6 ± 4.8 µV s. For the proximal stimulus point: amplitude of 8.3 ± 1.8 mV, latency of 5.65 ± 0.6 ms, CMAP duration of 6.6 ± 1.1 ms and area of 25.8 ± 4.6 µV s. Motor nerve conduction velocity (MNCV) of 63.5 ± 6.4 m/s. Distal latency and MNCV were significantly (p < 0.01) correlated with height, accounting for 38% and 33.5% of the variability, respectively. Female subjects had smaller distal latency and greater MNCV than male subjects (p < 0.01); this can be attributed to significant (p < 0.01) height differences between gender. No significant correlation between NCS parameters to age and BMI was found. The results demonstrate that the effect of height need to be taken into account when deriving normal values of NCS for ulnar motor nerve.