MEDIAN-ULNAR MOTOR LATENCY DIFFERENCE IN THE DIAGNOSIS OF CARPAL-TUNNEL SYNDROME

The differences between the distal motor latencies of the 2nd lumbrica l muscle (following stimulation of the median nerve) and the 2nd inter osseus muscle (stimulation of the ulnar nerve) were determined in 56 h ealthy volunteers and three patient groups: 20 with polyneuropathy (PN P), 76 with carpal tunnel syndrome (CTS), and 16 with CTS. and coexist ent PNP. The median-ulnar motor latency difference is less than 1,0 ms in normals and PNP patients but is significantly prolonged in both gr oups of CTS patients. The method has a sensitivity of 80 % in detectin g carpal tunnel syndrome compared to 83 % of the median sensory nerve conduction velocity and 71 % of the latency to the abductor pollicis b revis muscle, but it turned out to be the most spesific test for patho logical changes and is furthermore the only technique to detect a CTS in patients with underlying polyneuropathy.