Electromyography of the external anal sphincter - Comparison between needle and surface electrodes

PURPOSE: Electromyography of the external and sphincter is frequently used when investigating patients with defecation disorders. Investigations are o ften performed using an invasive technique by perineal insertion of a needl e or wire electrode. The aim of the present study was to investigate whethe r surface electromyography, with electrodes applied to the perineal skin, i s a reliable method in the diagnosis of paradoxical anal sphincter reaction . METHODS: Seventy-one patients with defecation disorders participated in t he present study. They were investigated with electromyography of the exter nal anal sphincter using surface and needle electrodes. RESULTS: In 65 of 7 1 (92 percent) patients the electromyography recording showed the same resu lt during straining using surface electrodes when compared with needle elec trodes. Twenty-two of these 65 patients had paradoxical anal sphincter reac tion, and 43 patients had decreased electromyography activity. In 65 of 71 (8 percent) patients the electromyography recording showed a different patt ern during straining using surface electrodes when compared with needle ele ctrodes. CONCLUSION: The present study demonstrates a good correlation betw een surface electrodes applied to the perineal skin and concentric needle e lectrodes in the diagnosis of paradoxical anal sphincter reaction. Noninvas ive electromyography recordings of the external anal sphincter are often pr eferred in the diagnosis of paradoxical anal sphincter reaction.