Automatic quantitative analysis of the electromyogram in partially denervated distal muscles: comparison with motor unit counting.

Using the ANOPS-101 minicomputer, an automatic analysis of muscle action potentials (MAP) was performed on a total of 53 extensor digitorum brevis (EDB) and abductor pollicis brevis (APB) muscles in patients with other evidence of denervation. The results were compared with observations made on 27 control subjects and they were also matched against estimates of functioning motor units made by the incremental stimulating technique of McComas et al (1971). Although the incidence of abnormal MAP parameters was relatively low in both muscles, it was possible to improve the diagnostic yield by combining the results for individual muscles. The relative merits and disadvantages of motor unit counting and automatic MAP analysis are discussed.