[Value of neurophysiological studies in diagnostic verification of carpal tunnel syndrome]

The success of surgical treatment of carpal tunnel syndrome depends largely on correct diagnosis. Nerve conduction studies are usually recommended, especially in cases where history and clinical signs are not very clear. The aim of this study is to show whether nerve conduction studies are helpful in confirming the diagnosis. Fifty-two cases of carpal tunnel decompression (39 patients, 13 male, 26 female, mean age 54 years) were included in the study. Prior to surgery, all patients underwent standardized nerve conduction studies. One patient who developed RSD was excluded. In 33 cases the history was typical for carpal tunnel syndrome (Phalen 1966). The surgical result was classified excellent in 67% and good in 33%. Nerve conduction studies had failed to confirm the diagnosis in five cases, although duration as well as severity of symptoms did not differ from the other cases. In 18 cases the patients' history was considered atypical. Nerve conduction studies indicated carpal tunnel syndrome in 89%. The result of median nerve decompression was satisfactory in 78% (excellent in 45% and good in 33%) and unsatisfactory in 22% of the cases. Notably patients with unsatisfactory results had positive nerve conduction studies. The Phalen and Hoffmann-Tinel testing produced no false-positive results in these cases. General analysis showed that age, severity and duration of symptoms did not significantly influence the result. However, patients with atypical symptoms had a higher incidence of radiological evidence of cervical spondyloarthritis (50 versus 30% in patients with typical symptoms). The results of our nerve conduction studies indicated a sensitivity of 85% and a specificity of 92%, comparable favourably with other reports. We conclude that in patients with classical symptoms nerve conduction studies are not absolutely necessary. However, when symptoms are atypical the diagnosis cannot be based on nerve conduction studies alone. The false-positive results delivered by the nerve conduction studies may be explained with the "double crush" theory, since cervical spondyloarthritis prevailed in patients with atypical symptoms.