Simplified orthodromic inching test in mild carpal tunnel syndrome

This prospective study was undertaken to determine the clinical relevance, reliability, sensitivity, and specificity of the orthodromic inching test w ith 2-cm incremental study of the median nerve over the four intracarpal ce ntimeters in 50 control and 50 successive (unselected) patient wrists with mild carpal tunnel syndrome (CTS). In controls, the mean maximum conduction delay per 2 cm (CD/2cm) was 0.445 +/- 0.04 ms, and abnormality was defined as at least one CD/2cm exceeding the mean + 2.5 SD of the normal CD/2cm. T his yielded a specificity of 98%. In patients with mild unselected CTS, thi s simplified orthodromic inching test (SOIT) detected the median nerve lesi on at the wrist in 47 cases (sensitivity = 94%). The SOIT detected 15 more CTS cases than did the orthodromic median-ulnar latency difference of the 4 th digit (Chi square = 13; P =.002). Thus, the SOIT was as effective as an incremental study every centimeter over 10 cm, and the time required for th e test allows its routine use when other electrodiagnostic tests fail to re veal any median nerve impairment. (C) 2001 John Wiley & Sons, Inc.