In early or mild carpal tunnel syndrome (CTS), conventional electrodiagnostic studies may show normal responses. In 50 hands from 50 control subjects and 16 hands from 10 CTS patients, mean values for latencies and amplitudes of the median and
ulnar
nerve were obtained, and then difference (median-ulnar) and ratio(median/ulnar) were calcuiated.
the difference of distal latency ratio(median/ulnar) and distal latency ratio (median/ulnar) in control and patients group were statistically significant. The amplitude ratios of median to ulnar sensory action potentials in control and patients
group
wee 1.23 and 0.80. respectively, and the difference between two groups were statistically significant.
Using discriminant analysis, it is suggested that the sensitive diagnostic methods of CTS are the ratio fo median sensory latencies stimulated at palm and wrist, the latency of median sensory nerve stimulated at wrist, the latency of median motor
nerve
stimulated at wrist and the difference between the distal motor latencies of median and ulnar nerve, in order of sensitivity.
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