The significance of second lumbrical-interosseous latency comparison in the diagnosis of carpal tunnel syndrome.

ABSTRACT

AIM: To assess the significance of the second lumbrical-interosseous latency (2LI-DML) comparison in the diagnosis of carpal tunnel syndrome (CTS). PATIENTS AND METHODS: We examined 150 consecutive hands of patients referred with suspected CTS, using the 2LI-DML test and other standard measures of median nerve function. Correlations of the 2LI-DML test with standard tests were computed. RESULTS: Hundred and four hands were electrophysiologically confirmed to have CTS. The 2LI-DML test was abnormal in 99/104 (95.2%) hands with CTS with a mean value of 1.54 +/- 1.12 ms. Among the other measures, the orthodromic median-ulnar palmar velocity comparison was the most frequently abnormal test (95/104 hands, 91.3%), followed by the double-peak morphology of orthodromic sensory action potential from digit 4 (94/104, 90.4%). The 2LI-DML test significantly correlated, either positively or negatively, with all other standard tests. CONCLUSION: The 2LI-DML comparison is highly sensitive in diagnosing CTS, even in mild cases in which standard tests fail to detect abnormalities.