Standardization of anal sphincter electromyography: effect of chronic constipation.

Severe chronic constipation has been implicated as a cause of damage to the pelvic floor innervation. The aim of the present study was to examine the role of mild to moderate chronic constipation, a condition more relevant for clinical electromyographers, because this complaint is common in patients sent for evaluation of possible neurogenic dysfunction of lower sacral myotomes. A group of 59 subjects without major uroneurological dysfunction, proctological disorders, or neurological abnormalities participated in the study, which involved concentric needle electromyography of the external anal sphincter (EAS). Motor unit potentials (MUPs; sampled using multi-MUP analysis) and interference pattern (IP, sampled using turn/amplitude analysis) of chronically constipated and control subjects were compared. No effect of chronic constipation on MUP/IP parameters compatible with neurogenic injury was found. Our results suggest that mild chronic constipation does not cause damage to the EAS innervation, and that no separate reference values are needed for this group of subjects.