Percutaneous sacral neurostimulation of penile erection during radical prostatectomy: surgical technique

Intraoperative neurophysiological monitoring (IONM) has been introduced as a potentially useful adjunct technology when performing pelvic surgeries such as radical prostatectomy for improving postoperative functional outcomes. It involves surveying the functional integrity of critical intrapelvic nerve structures in conjunction with registering neuronally mediated functional effects in the pelvic region during surgery, such that intraoperative adjustments can be made with the intent to minimize iatrogenic nerve injury. Such critical nerve structures include the periprostatic cavernous nerves, the source of neurochemical mediators of penile erection and urinary continence. To implement this technology, a neuronal stimulus is needed for activating physiological responses in the pelvic region. As such, we describe an innovative technical procedure for applying neurostimulation at the sacral spinal cord, bearing in mind the significance of this spinal level in neuroregulating pelvic functions, including penile tumescence and urethral sphincteric activity. Our procedure involves percutaneous insertion of 26-gauge, 50-mm monopolar insulated needle electrodes into the low back, guided by external physical landmarks, that contact the laminae at the fourth and fifth lumbar vertebral levels, from which an electrical current is delivered, thereby driving sacral spinal cord neural impulses to pelvic organs and structures. We performed the procedure in a pilot investigation of patients undergoing open radical prostatectomy just prior to surgical dissection of the prostate, assessing tumescence responses using a proprietary Sentinel^® functional near-infrared spectrophotometry sensor cuff placed on the penis. In five patients with mild or no erectile dysfunction preoperatively, we recorded higher than baseline variance in oxygenated and deoxygenated hemoglobin concentrations after neurostimulation (P<0.05), consistent with the onset of penile tumescence. In two patients with moderate to severe erectile dysfunction, neurostimulation did not elicit significant spectrophotometric changes or penile tumescence. There were no adverse events related to this procedure. Our findings suggest that sacral neurostimulation using a percutaneous needle electrode insertion technique is a feasible and safe procedure that may be used intraoperatively during radical prostatectomy to induce penile erection. Its potential role for assessing the functional integrity of neuroregulated erectile function in an IONM platform for radical prostatectomy surgeries is proposed, although further investigation is needed to demonstrate its utility for this purpose.