Journal of Neurology, Neurosurgery, and Psychiatry 1983;46:1115-1118 The use of conventional electromyography to assess external sphincter neuropathy in man

SUMMARY Conventional electromyography was used to measure motor unit potential duration in the external anal sphincter in normal subjects and patients with idiopathic faecal incontinence. The results revealed a direct correlation between age and mean motor unit potential duration in control subjects, but no differences between age-matched male and female subjects. Patients with faecal incontinence exhibited prolongation of mean motor unit potential duration compared with matched controls. This technique provided useful quantitative data on reinnervation within the anal sphincter, complementing the results of single fibre electromyography. Recent work has indicated that most patients with idiopathic faecal incontinence have denervation of the external anal sphincter.'-4 This conclusion is based on histological examination of muscle speci-mens, taken at operation, ' 2 and on single fibre elec-tromyography (SFEMG).34 Conventional elec-tromyography has been used previously to record motor unit potentials from normal anal sphincters and to demonstrate some of the qualitative abnor-malities that may be found in neuropathic sphincter muscle.8 This technique was applied in a systematic quantitative manner to study motor nerve regenera-tion within the anal sphincter. Material and methods Subjects Recordings were taken from 18 patients (17 female, one male; aged 38 to 93 years, mean = 69 years) and 20 nor-mal controls (eight males, 12 females; aged 20 to 80 years, mean age 56 years). The controls were hospital patients with disorders not affecting the gastrointestinal or nervous systems. Informed consent was obtained in all cases, and the study was approved by the Ethical Committee of th