The effect of provocative tests on electrodiagnosis criteria in clinical carpal tunnel syndrome.

INTRODUCTION AND OBJECTIVE: Nerve conduction study is the most sensitive test for diagnosis of carpal tunnel syndrome (CTS). This test is normal in some patients with mild CTS. Median nerve conduction study evaluation after a provocative test (e.g. wrist flexion) may be helpful for diagnosis of mild CTS. This study aimed to determine the effect of wrist flexion on median nerve conduction in patients suspected to CTS and in healthy subjects.

MATERIALS AND METHODS: In this case-control study, 20 patients (20 hands) with clinical signs of CTS and normal routine electrodiagnosis test results and 20 healthy subjects were investigated. Measured parameters included: median nerve distal sensory latency (DSL), nerve conduction velocity (NCV) across wrist, compound nerve action potential (CNAP), distal motor latency (DML) and compound muscle action potential amplitude (CAMPAMP). The above noted parameters were measured before and after 5min of full wrist flexion. Data were analyzed using paired T-test.

RESULTS: Distal sensory latency increment and NCV decrimental after 5 min of wrist flexion in the patients group were statistically significant (p<0.01). The same parameters did not show significant incremental or detrimental changes in the control group.

CONCLUSION: Median nerve DSL and NCV measurement after 5 min of wrist flexion may be helpful in determining more sensitive parameters in the electrodiagnosis of CTS.