Objective
To know whether nerve conduction study (NCS) could predict later development of carpal tunnel syndrome (CTS) in asymptomatic hands of the patients with unilateral CTS. Method: Thirty four patients with unilateral CTS were studied. Subjects were divided into groups with or without the delay of latency, based on the results of initial NCS of asymptomatic hands. After follow up for more than 6 months clinically and electrodiagnostically, the development of CTS in initially asymptomatic hands was compared between groups. Results: At follow up, CTS was diagnosed in 83% of the subjects in the group with motor latency delay at first study, while it was diagnosed in 32% of the subjects in the group without motor latency delay. In the group with sensory latency delay at first study, CTS was diagnosed in 78% of subjects at follow up, whereas only 19% of the subjects developed CTS in the group without sensory latency delay. The incidence of CTS at follow up was significantly higher in the group with motor or sensory latency delay at first study. Conclusion: In unilateral CTS, latency delay in motor or sensory NCS of asymptomatic hands may suggest a greater risk of later development of CTS. (J Korean Acad Rehab Med 2006; 30: 575-579)