Pudendal nerve evoked potential monitoring in procedures involving low sacral fixation

Pudendal nerve evoked potentials were used in orthopaedic surgical procedures involving fixation below the S1 level. Pudendal nerve stimulation was used to monitor 154 patients. Eleven patients (7.14%) had responses that were either difficult or impossible to interpret in that they were not consistently replicable. In one case (0.65%), responses were lost during surgery, and there were no subsequent neurologic sequelae (false-positive response). No patients had postoperative deficit to the sacral roots or to the global cord. Although it is possible to obtain definitive dermatomal responses down to S1, the use of pudendal nerve stimulation was found to provide additional means of monitoring lower sacral roots. Since the pudendal nerve is intimately associated with bowel, bladder, and sexual dysfunction, easily obtainable routine monitoring of this nerve can provide significant safety that the conventional somatosensory and dermatomal responses give to higher spinal levels.