Intraoperative cavernous nerve stimulation during nerve sparing radical prostatectomy: how and when?

Although nerve-sparing prostatectomy is widely practiced, the results with respect to potency preservation often do not meet expectations. The concept of intraoperative cavernous nerve stimulation is rational. Recent data that link the response to sildenafil after prostatectomy to bilateral nerve sparing has increased the importance of optimizing nerve sparing. The cavernous nerves are often difficult to visualize and may have a variable course. A tumescent response to nerve stimulation can be consistently demonstrated. The response may be subtle, and characterized by a minimal increase in penile circumference and blood flow. Immediately after prostectomy, proximal nerve stimulation identifies whether neural continuity has been maintained, and is predictive of recovery of erectile function. A new device, the Cavermap, has been developed to permit intraoperative nerve stimulation with tumescence monitoring. An initial phase 2 and subsequent phase 3 single blinded, randomized, multicenter study that compared Cavermap-assisted prostatectomy with conventional nerve sparing demonstrated a significant benefit in terms of the duration of nocturnal tumescence by Rigiscan (Timm Medical Technologies, Eden Prairie, Minnesota) at 1 year. Other approaches are being explored, including sural nerve grafting, use of nerve stimulation during cystectomy or abdominal-perineal resection, and direct corpus cavernosum pressure monitoring during nerve stimulation. These approaches warrant further evaluation.