The impact of wrist extension provocation on current perception thresholds in patients with carpal tunnel syndrome: a pilot study.

Purpose: To determine whether current perception threshold (CPT) varied between subjects with and without carpal tunnel syndrome (CTS) and whether positioning in wrist extension (reversed Phalen's test) was provocative.

Method: Subjects (n=30) were tested using the Neurometer (Neutron, Inc., Baltimore, MD) at 5, 250, and 2,000 Hz in a rest and reverse Phalen's position. Group and positional differences were analyzed using analysis of variance.

Results: Higher CPT occurred at 2,000 Hz in both rest (p=0.02) and reverse Phalen's position (p=0.01) in CTS subjects. There was also a significant change in CPT in the CTS group following wrist extension, particularly at 2,000 Hz (p<0.05).

Conclusion: A positional effect on sensibility was noted at 2,000 Hz in subjects with CTS. Further evaluation is required to determine the role and optimal test protocols for provocative-sensory testing in diagnosis and outcome assessment of CTS. For CPT these should focus on using the 2,000 Hz frequency.