Objective
High body temperature may alter nerve conduction in demyelinated neurons. This study was designed to investigate the changes in nerve conduction parameters in response to the heat applied over the wrist in the patients with carpal tunnel syndrome (CTS).

Method
16 hands of CTS patients and 16 hands of normal subjects were involved in this study. Motor and sensory nerve responses were measured at 32^oC and 42^oC in all the subjects. Infrared was applied on the wrist to warm the skin to 42^oC. Changes of relative amplitude, duration, and latency of evoked potentials in median sensory and motor nerves of CTS patients were compared with those of the normal subjects. Correlation between the latency measured at 32^oC and changes of amplitude of motor and sensory nerve responses after warming to 42^oC was evaluated in CTS group.

Results
Relative reduction in duration of motor responses in CTS group was significantly greater than in normal group. Relative reduction of motor and sensory amplitude, and sensory latency were greater in CTS. There was no significant relation between motor and sensory latency at 32^oC and relative amplitude reduction in motor and sensory responses at 42^oC.

Conclusion
Increase in temperature may increase the number of blocked nerve fibers in patients with CTS than in normal subjects.