Sensitivity of the various tests for the diagnosis of carpal tunnel syndrome.

The electrophysiological results of a prospective study of 150 successive cases of carpal tunnel syndrome in 96 patients are reported to evaluate the sensitivity of nine different electrophysiological tests and thresholds for the diagnosis of carpal tunnel syndrome. The distal motor latency was > 5 ms in 35% of cases and > or = 4 ms in 55% of cases. The distal sensory latency from the PIP joint of the middle finger was up to 3.4 ms in 61% of cases. The middle finger orthodromic conduction velocity (14 cm) was < or = 45 m/s in 66% of cases and the orthodromic conduction velocity after palmar stimulation (8 cm) was < or = 45 m/s in 76%. The remaining 24% of cases were assessed by special tests such as specific median-ulnar latency difference (21%), and the centimetric test was altered in all. Highly sensitive tests are required to assess or exclude the diagnosis in one quarter of cases of carpal tunnel syndrome. Although the specific median-ulnar latency difference is the easiest test to perform, the centimetric test is the most valuable for the assessment of the mildest forms of carpal tunnel syndrome.