Effect of Median Nerve Compression Test on the Nerve Conduction Speed in Carpal Tunnel Syndrome

Objective To determine the effect of median nerve compression on median nerve conduction speed in patients with carpal tunnel syndrome(CTS).Methods In this case-control study,29 subjects were enrolled.CTS group included 14 patients(22 hands) with CTS confirmed by electrodiagnostic studies,while the control group included 15 healthy subjects(30 hands).The across wrist nerve conduction of median and ulnar nerve was measured when the wrist was in neutral position.Measured parameters included distal sensory latency(DSL),sensory nerve action potential(SNAP),sensory conduction velocity(SCV),distal motor latency(DML) and compound muscle action potential(CMAP).Sensory nerve conductions were tested first,and then the motor nerve conduction.The patients were asked to perform the median nerve compression test by flexing elbows,pronating forearm and pushing the dorsal surfaces of both hands together into maximum wrist flexion for 5 minutes.Then the above parameters were measured again.Results By electrodiagnostic studies,22 hands and 24 bands were diagnosed with CTS before and after the median nerve compression test,respectively.After the compression test,the median nerve DSL were significantly prolonged in CTS group(P0.05) but no significant differences were found in the median nerve DML(P0.05).The parameters of ulnar nerve in group CTS and median nerve and ulnar nerve in control group failed to show any significant change(P0.05).The CTS group had longer median nerve DSL and DML than the control groups(P0.05),but the differences in ulnar nerve DSL and DML were not significantly between the two groups.Conclusion A 5-minute median nerve compression test may make the median nerve DSL prolonged and may be a helpful diagnosis of early CTS.