Objective: To investigate the reliability of distoproximal latency ratio of median sensory nerve as a diagnostic criterion of carpal tunnel syndrome (CTS) in patients with diabetic polyneuropathy.

Subject: Electrophysiologic study was performed in 264 hands of 208 patients with diabetes. Forty eight hands (24 subjects) without diabetes mellitus or CTS were included as a normal control group. Another 48 hands having CTS without diabetes mellitus were also included as a CTS control group.

Method: Clinical and electrophysiologic findings were included to detect carpal tunnel syndrome in patients with diabetic neuropathy. Sensitivity and specificity of various electrodiagnostic parameters to confirm clinical CTS were obtained.

Results: Diabetic neuropathy was diagnosed in 66.3%, and median neuropathy was diagnosed in 52.7%. CTS was found in 32.2% as determined by the distoproximal latency ratio. The sensitivity of distoproximal latency ratio as a diagnostic tool for CTS was the highest (95.1%) and the specificity was the second highest (51.3%) among 5 different electrodiagnostic criteria of CTS.

Conclusion: The results suggest that distoproximal latency ratio is an important parameter with high sensitivity in determining CTS in the patients with diabetic polyneuropathy.

Keywords :Diabetic neuropathy, Carpal tunnel syndrome, Distoproximal latency ratio