Electrophysiological correlate of the phalen test

Abstract

Objective: To investigate whether flexing the wrists, as in the Phalen test, results in slowing of the median distal motor latency (DML) or distal sensory latencies (DSL) in comparison with the ulnar nerve, in patients with the carpal tunnel syndrome (CTS).; Design: We performed nerve conduction studies on the median and ulnar nerves of 54 hands. We studied the DML and DSL at rest and upon wrist flexion for 1 and 3 minutes. We compared the results of the median nerve to that of the ulnar nerve during the different test conditions. We correlated our results with the clinical presence or absence of the Phalen sign.; Settings: The study was performed at the clinical neurophysiology laboratory of the department of neurology, at the American University Medical Center in Beirut, Lebanon.; Participants: The participants were patients with the clinical diagnosis of CTS referred to the laboratory for the electrophysiological evaluation of the median nerve in the carpal tunnel.; Intervention: Not applicable.; Main outcome measure: The main outcome measures were the DML and the DSL in the median nerves across the carpal tunnel in comparison with the ulnar nerves.; Results: We concluded that flexing the wrist for 1 or 3 minutes does not change the distal motor or sensory latencies of the median nerve to any statistical significance in comparison with the ulnar nerve irrespective of the degree of median nerve compression, and that there is no correlation with the Phalen sign.; Conclusions: The significance of this study is that flexing the wrist as in the Phalen test does not correlate with compression of the median nerve neither in normal wrists nor in patients with different degrees of CTS. Copyright © 2013 by Lippincott Williams & Wilkins.