Patients attending the medical clinic of a local hospital (Kwong Wah Hospital) complaining of finger or hand numbness are referred to the electro-neuro-diagnostic unit for nerve conduction test. Consecutive patients with clinical and electrophysiological features of CTS are invited to participate in the study. Clinical features are pain, paresthesia or weakness in the median nerve distribution for at least 3 months. The neurodiagnostic criteria are based on the American Academy of Neurology summary statement, which further classifies the abnormalities as follows: (1) mild abnormality, i.e., abnormal comparative tests or prolonged median distal sensory latency (DSL > 3.5 ms) but normal median distal motor latency (DML); (2) moderate abnormality, i.e., prolonged median DSL and DML (⩾4.2 ms); and (3) severe abnormality, i.e., absence of median sensory nerve action potential and prolonged median DML or absent compound muscle action potentials.