Median nerve conduction tests and Phalen's sign in carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) is associated with sensory and/or motor dysfunction of the hand's fingers. The syndrome is caused by a continuous or intermittent pressure on the median nerve (NM) at the patient's wrist. 82 patients suffering from recent CTS symptoms, and 24 matched asymptomatic controls were tested. In the present study we examined five electrophysiological parameters and their correlations with a most commonly used clinical test--the Phalen test. The Phalen measure is the time from initial provocation until positive sign. The electrophysiological measurements are: NM Onset Sensory Velocity, NM Peak Sensory Velocity, NM Motor Nerve Velocity, NM Distal Motor Velocity, NM Residual Latency. Most of the symptomatic hands exhibited pathological values of their clinical or electrophysiological parameters. Phalen and Residual Latency were the most sensitive parameters. Phalen times were not significantly correlated with any of the five electrophysiological parameters, yet sensory velocity tended to decrease in patients with pathological Phalen values.