Simplified Evaluation of the Paradoxical Puborectalis Contraction With Surface Electrodes

PURPOSE: Paradoxical puborectalis contraction during defecation is one possible explanation for constipation. The degree of paradoxical contraction can be evaluated by intramuscular electromyography from the puborectalis and external anal sphincter muscles. This study aimed to determine whether a noninvasive technique with surface electrodes placed over the subcutaneous part of the external anal sphincter is feasible in the evaluation of paradoxical activity. METHODS: Twenty-five patients with constipation were studied. Sphincter muscle activity during strain and squeeze maneuvers was recorded using surface electrodes placed 1 cm from the anal verge. In addition, intramuscular recordings were made simultaneously from the external anal sphincter and puborectalis muscles. The degree of paradoxical activation was calculated as a strain/squeeze index. The patients were examined either in the left lateral position or sitting on a commode. RESULTS: The study revealed significant (P < .01) correlations between indices obtained from the surface anal sphincter recordings and the intramuscular recordings (from the external anal sphincter and the puborectalis muscles). CONCLUSION: Surface recordings from the external anal sphincter seem to be an equally reliable, less time consuming, and less painful alternative to invasive measurements of paradoxical activity. In a few patients, however, invasive recordings may still be required.