Automatic carpal tunnel syndrome tester

Objective: A device for automatic testing of sensory latency across the carpal tunnel is described. A fixed bar contains a stimulating electrode distally and a bipolar recording set up with the two poles at 7 and 14 cm distance proximally. The device is thus based on the so called 14/7 method, using orthodromic testing. Methods: Automatic testing of electrode resistance and muscle relaxation precedes the self triggered start of stimulation. The latencies are analyzed according to a special algorithm. The proximal/distal latency index is increased in carpal tunnel syndrome (CTS). Results: Healthy controls (32 hands in 32 subjects) and patients referred with suspicion of CTS (258 hands) were studied with the new device, by conventional technique and sometimes by inching (centimetering) across the carpal tunnel. A positive CTS result with the tester was in accordance with the routine test in 94% of the patients. Conversely, routine studies showed CTS in 118 hands. Among those, the tester agreed in 44, showed no signals in 70 and indicated normal findings in 4 hands. In cases with a combination of polyneuropathy and CTS, the CTS was detected in 5 out of 6 cases. A complete test takes about 1 min per hand. Conclusions: The results are very promising.