Clinical utility of residual latency in ulnar neuropathy at elbow: Is there any correlation?

BACKGROUND: Residual latency is the time difference between measured and predicted distal conduction time. We investigated ulnar nerve residual latency in patients with ulnar neuropathy at elbow for the possibility of its clinical utility. MATERIALS AND METHODS: In a cross-sectional study and based on the inclusion and exclusion criteria, ulnar nerve residual latency was calculated by using standard settings in 63 hands of patients who had signs and symptoms suggesting ulnar neuropathy at elbow and 94 healthy hands as the control group. RESULTS: Mean ulnar nerve residual latency for case and control groups were 1.82 ± 0.45 and 1.59 ± 0.54 ms, respectively, which showed a statistically significant difference (P = 0.01). There was no significant difference in mean ulnar nerve residual latency between males and females and also between right and left hands (P > 0.05). By considering different cut-off points, the sensitivity and specificity of a residual latency of 2.86 ms were 70% and 56%, respectively. CONCLUSION: Ulnar nerve residual latency may reflect the effects of an axonal injury at elbow on distal ulnar motor fibers. So, its measurement may help in the diagnosis of ulnar neuropathy at elbow.