Orthodromic inching test in mild carpal tunnel syndrome.

The Orthodromic inching test of the median nerve at wrist was performed on the dominant wrist of 80 controls and of 100 patients with mild carpal tunnel syndrome defined by the presence of clinical features and normal classical electrodiagnostic tests. In controls the mean conduction delay per centimeter (CD/cm) was 0.184ms and was slightly higher inside than outside the carpal tunnel; the maximal CD/cm (MCD/cm) was never greater than 0.34ms (mean 0.247). In patient the MCD/cm was 0.36 ms or more in 96 patients. This abnormality was located within the carpal tunnel in 92% of cases. Outside the entrapment site CD/cm values remained normal and similar to those found in the controls. On the whole, this results in an overall specificity of 100% and sensitivity of 96% for the Orthodromic inching test.