A comparison of EMG procedures in the carpal tunnel syndrome with clinical-EMG correlations.

One hundred and twenty-two patients were selected on the basis of symptoms of finger numbness and tingling thought to suggest carpal tunnel syndrome. The severity of the symptoms was graded and the patients were studied with seven established EMG procedures, motor inching to the abductor pollicis brevis and second lumbrical muscles, and sensory inching. Symptom severity was compared with the degree of nerve conduction abnormality and results from symptomatic hands with those abnormal results from patient's asymptomatic hands. Motor inching to the abductor pollicis brevis muscle was the most sensitive study and, when combined with sensory inching, gave a sensitivity of 97-100% (depending on symptom severity). Motor inching to the second lumbrical muscle alone detected the lesion site in several severely involved nerves. Guidelines are suggested with which one can estimate the likelihood that a patient's finger sensory symptoms are on the basis of carpal tunnel syndrome.