The carpal tunnel syndrome. Relationship between median distal motor latency and graded results of needle electromyography.

Needle Electromyography (NEMG) was performed in 228 patients who had been diagnosed by means of motor and sensory median nerve conductions of having Carpal Tunnel Syndrome (CTS). Evaluating abnormal spontaneous muscle activity (fibrillations, positive sharp waves, fasciculation potentials and myokymic discharges) and recruitment pattern, 51.7% of them showed abnormal NEMG. According to the amount of abnormality found, the studies were classified into: normal, grade 1, grade 2 and grade 3. Median Distal Motor Latency (DML) to APB was prolonged beyond the upper confidence limit in 155 (68%) hands, showing a mean value of 5.69 +/- 2.79 msec. Statistically significant difference (p < 0.001) of DML mean value among patients with a NEMG "normal", "grade 1" or "grade 2" have been found. We revise previous reports about NEMG on the CTS and discuss practical consequences of our findings.