Reference values of motor unit potentials (MUPs) of the external anal sphincter muscle

Objective: To provide reference values for the isolated motor unit potentials (MUPs) in the external anal sphincter (EAS) muscle, as mean duration, mean amplitude, mean area, number of turns and number of phases, related to the age of the patient. These data are not available in worldwide literature in spite of the fact that the EAS muscle is being increasingly mentioned in relation to differential diagnosis. Methods: Study of 235 subjects aged 0–80 years using an automated analysis program. Results: The study performed shows a clear gradual progression of the mean duration with patient age. The variability of all other parameters tested is also analyzed. Conclusions: Our study shows that the classical values of MUPs isolated in the EAS muscle are directly related to age, and that this method is fully reliable to study its pathological conditions.