Relation of wrist angles to median nerve conduction studies.

Objectives: To measure the changes in median nerve conduction parameters at various angles of wrist flexion and extension.

Design: We studied 8 patients with carpal tunnel syndrome (CTS) and 4 subjects (5 hands) without the condition (controls). Conduction parameters were measured with the wrist in neutral position and at different wrist angles.

Results: Onset motor latency increased in both groups with wrist extension and decreased with wrist flexion. Sensory onset latency decreased in both groups with wrist flexion. Compound Muscle Action Potential (CMAP) amplitude increased with wrist flexion for both groups. Wrist extension resulted in reduction of the CMAP amplitude in controls; however, for the CTS group it increased for the first 30 degrees and then decreased. Sensory Nerve Action Potential (SNAP) amplitude increased with wrist flexion and decreased with wrist extension in both groups.

Conclusion: Median nerve conduction parameters improve with wrist flexion and generally worsen with extension.