Nerve stimulation may help preserve erectile function
Enhancements to nerve sparing during prostatectomy help patients postoperatively

Zvi Wirschubsky, MD, PhD

UT  CORRESPONDANT

Stockholm, Sweden--A tumescence response to nerve stimulation may guide urologists in preserving cavernosal nerves and improving erectile function following radical prostatectomy. Previous studies have sbown different rates of erectile failure after this procedure because neuromuscular bundles may be obscured during surgery by bleeding, over­lying tissue, surrounding fat, or blood vessels. Nerve sparing may be offered to improve the Out­come for patients undergoing prostatectomy.

During the European Association of Urology Congress here, two groups presented their results with nerve-sparing prostatectomy. Laurence Klotz, MD, and colleagues from the Division of Urology, Sunnybrook Health Sciences Centre, University of Toronto, Canada, discussed their 1-year follow-up results with 25 patients who were analyzed with a nerve stimulator and tumescence monitor device (CaverMap, Blue Torch Inc., Ashland, MA) during radical prostatectomy.

"For many surgeons, nerve sparing comes to rest near the bottom of a priority list, which consists of achieving cancer-free status with negative margins, minimizing blood loss, keeping operation time down, and teaching the technique to fellows, resi­dents, and students," Dr. Klotz said.

Studies on animals and humans have previously demonstrated that the electrical stimulation of the cavernous nerve increases pressure in the cavernous bodies and can produce a vis­ible tumescence response. The de­vice was used to identify the course of the cavernous nerves and guide the surgeon in avoiding nerve damage. Based on presence or absence of confirmed response, more informed decisions could be made regarding the dissection strategy for optimal preservation of the erectile nerves.

Nineteen patients were potent pre­operatively and had surgical condi­tions that permitted intranperative stimulation and nerve sparing.

Eighty-nine percent of patients had a tumescence response during nerve stimulation. Five patients reported nor­mal erectile function, while 11 reported partial function, defined as occasional erections suffi­cient for intercourse. Two patients with preoperative erectile failure exhibited an intraoperative tumescence response. There were no ap­parent adverse effects from using the device.

Only 12% of patients had positive margins confined to the lateral margin and/or apex, in whom the modifications associated with nerve sparing conceivably could have altered margin status. This clinical data suggests that stimulation of the cavernosal nerves while monitoring changes in penile tumescence to map the course of the nerves improves nerve sparing and erectile function following radical prostatectomy.

The nerve locator device forces the surgeon to pay particular attention to the nerve-sparing component of the operation and to allocate the time and effort required to perform it optimally. A phase if randomized study using preoperative evaluation with Rigi-Scan (Timm Medical Technologies, lnc., Eden Prairie, MN) and at 1 year post-operatively recently has been carried out to confirm these findings.

Effectiveness of electrostimulation

Uwe H.G. Michl, MD, and Hartwig Huland, MD, of the deparanent of urology, University of Hamburg, Germany, evaluated the effectiveness of intraoperative electrostimulation for identification of the erectile nerves.

"The functional anatomy of the erectile nerves is variable," Dr. Michl said. "Intraoperative electrostimulation of the erectile nerves needs a special kind of anesthesia, as well as local blocking of alpha receptors."

A total of 18 men undergoing nerve-sparing prostatectomy were analyzed with intracavernosal pressure (ICP) directly from December 1996 through September 1997. Two separate needle electrodes were used for stimulation. ICP was recorded with a needle connected to a pressure transducer, and stimulation was performed under normal or total intravenous anesthesia (TIVA).

Sympathetic nerves were blocked by intracavernosal injection of urapidil, 5 mg, at the beginning of the operation, which led to a significant increase in ICP during electrostimulation and could be measured in all patients. Without TIVA and without urapidil, only inconstant reactions (CS cm water) were recorded.

Urapidil caused a slight rise of ICP. Stimulation of the nerves beside the prostate re­sulted in an initial decrease of ICP, followed by a continuous increase of up to 60 cm water with visible erection. The reaction was more pronounced during stimulation next to the seminal vesicles, and a sharp rise of ICP occurred by stimulation lateral of the seminal vesicles. Stimulation of an intermediate position showed a sharp rise of ICP followed by a continuous increase. Follow-up over a minimum of 12 months showed improved potency.

"Our data clearly shows that intra­operative stimulation of selective erectile nerves is effective and seems to be a valuable tool for their preservation," Dr. Michl said. "Postoperative potency increased with intra-operative electrostimulation."

The Canadian study was sup­ported by a grant from UroMed. UT

©Reprinted from DERMATOLOGY TIMES, June 1999 AN ADVANSTAR * PUBLICATION Printed in U.S.A.