[The centimeter test: diagnostic test for beginning carpal tunnel syndrome]

This study, in 13 control subjects, assesses the normal value of the centimeter conduction delay (CCD). The mean CCD is 0.184 ms, the maximum CCD is less than 0.40 ms and the ratio between maximum and normal CCD never exceeds 2. In 47 patients with clinical features of carpal tunnel syndrome and normal classical EMG data, the centimeter test selected two groups. The first consists in 32 patients with a pathological maximum CCD varying from 0.36 to 1.10 ms and a maximum to normal CCD mean ratio of 3.75. The second group consists in 15 patients with a maximum CCD between 0.21 and 0.39 ms and a maximum to normal CCD mean ratio of 1.52.