Reference ranges and impact factors of quantitative electromyography of external anal sphincter

Abstract

Objective To establish a practical reference range on anal sphincter electromyography of healthy volunteers with different physiological characters. Methods A group of 62 healthy volunteers were recruited from April to June 2013 in Peking Union Medical College Hospital through public recruitment for the reference value study of anal sphincter electromyography, including 37 women with various childbirth experiences and 25 men. Motor unit potentials were obtained from bilateral external anal sphincter of each subject by standard concentric electromyography needle. For each subject, the mean values of each motor unit potential parameter (including duration, amplitude, area, mean number of turns, mean number of phases) and the satellite rate were calculated. The reference ranges of each parameter were statistically calculated for various subject characteristics. Results The mean duration of the motor unit potentials of all subjects was (9.92±1.31) ms and the mean satellite rate was 7%±5%. The reference ranges of durations (means±1.96 s) were 7.91-12.19 ms for men, 7.43-10.47 ms for women without vaginal delivery experiences and 7.50-13.54 ms for women with vaginal delivery experiences. The upper limits of satellite rates (means+ 1.65 s) were 13% for men and women without vaginal delivery experiences and 20% for women with vaginal delivery experiences. Conclusions A practical reference range on anal sphincter electromyography with discriminating physiological characters was established. The changes of anal sphincter electromyography in women with vaginal delivery experiences were complicated, which should be carefully interpreted. Key words: External anal sphincter; Electromyography; Reference ranges