Ulnar 14-cm and 7-cm antidromic sensory studies to the fifth digit: reference values derived from a large population of normal subjects.

The ulnar antidromic sensory conduction study to the fifth digit is commonly performed in clinical electrodiagnosis. Several authors have published normal ranges for this study, but these published reports have been limited by generally small sample sizes. The purpose of this article is to present a large database of normal ranges for this nerve study. After obtaining Institutional Review Board approval, 258 asymptomatic subjects were tested bilaterally with an ulnar antidromic sensory technique recording from the fifth digit. Stimulation was performed 7 cm and 14 cm proximal to the recording electrode. Onset latency, peak latency, onset-to-peak amplitude, peak-to-peak amplitude, area, duration, and rise time were recorded. Side-to-side and 14- to 7-cm comparisons were made. A repeated measures analysis of variance was performed to determine whether any of the subjects' demographic characteristics of age, race, gender, height, or body mass index (kg/m2) were associated with different results for the nerve conduction measures. Increasing age and body mass index were found to correlate with decreasing amplitude and area. No other correlations were noted between the results and the physical characteristics. Mean onset latency was 1.4 +/- 0.2 ms at 7-cm and 2.6 +/- 0.2 ms at 14-cm stimulation. Mean peak latency was 2.0 +/- 0.2 ms at 7-cm and 3.4 +/- 0.3 ms at 14-cm stimulation. Mean onset-to-peak amplitude was 32 +/- 20 microV at 7-cm and 33 +/- 17 microV at 14-cm stimulation. Mean negative-to-positive-peak amplitude was 55 +/- 36 microV at 7-cm and 50 +/- 32 microV at 14-cm stimulation. Mean side-to-side difference for onset latency was 0 +/- 0.2 ms. Additional data is presented in the study.