Electrophysiological study of motor nerve supply of pelvic floor.

Direct stimulation of a branch of the sacral nerves which lies above the pelvic floor and electromyographic recording of activity in the muscles of the pelvic floor showed that this nerve supplied the puborectalis muscle in 19 of the 20 nerves studied in 16 patients. Similar results were obtained when this nerve was stimulated in 2 patients undergoing anterior resection of the rectum. The pudendal nerve was also directly stimulated in 3 patients and found to supply only the ipsilateral external anal sphincter muscles. These findings suggest that the motor nerve supply of the important muscle of continence usually lies above the pelvic floor and not below it as previously believed.