Radial nerve conduction in patients with carpal tunnel syndrome.

Orthodromic sensory nerve conduction was studied in the distal segment of the superficial radial nerve in 50 cases of carpal tunnel syndrome in 41 patients. In patients aged 50 years or less, the mean conduction velocity was 48.6 m/s (SD +/- 4.8), and the mean amplitude of the sensory action potential was 9.7 microV (SD +/- 4.0). For patients aged over 50 years, the corresponding values were 46.4 m/s (SD +/- 5.5) and 7.5 microV (SD + 3.5). It is important to demonstrate normal radial nerve conduction in patients with carpal tunnel syndrome in order to exclude peripheral neuropathy or cervical radiculopathy. Spread of activity from the radial nerve may be mistaken for a median nerve potential.