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'Nerve Mapping' Helps
Preserve Erectile Function

October 26, 98. Urologists are evaluating a new surgical tool that can help spare some men from becoming impotent after surgery for localized prostate cancer. The aim is to enhance and improve existing nerve-sparing surgery.
     The new tool aids surgeons in pinpointing the microscopic nerves around the prostate that control sexual function, so that they can avoid damaging these nerves during prostate removal, said James Brooks, MD, an assistant professor of urology who is participating in a national, multi-center study of the device.
     "It's a useful tool to help us locate those nerves and decrease the side effects of the operation. I think it has great potential for decreasing impotence after radical prostatectomy [prostate removal]," said Brooks, who practices with the Stanford Urology Clinic, part of UCSF Stanford Health Care.
     The device, approved in the USA a year ago by the Food and Drug Administration, works by delivering a low-level electrical stimulus to the nerves around the prostate and then measuring the erection response. Through this process, the device helps produce a map of these critical nerves, which are invisible to the naked eye, so that doctors can navigate around them during surgery.
     By simplifying an otherwise challenging surgical procedure, the new tool ultimately could make nerve-sparing surgeries much more widely available to prostate cancer patients, Brooks said. "Doctors will be able to figure out where the nerves are, map them out and save them," he said. "So I think this will be a boon to surgery."
     Men with cancers that have spread beyond the prostate are not candidates for nerve-sparing procedures, he noted. Brooks is currently the only physician in Northern California who is using the new device, which is being evaluated on a large scale at 21 medical centers across the country. The device, called the CaverMap Surgical Aid, is made by UroMed, a biomedical company in Needham, Mass.

Getting consistent results
The field of prostate surgery took a major leap forward in 1982, when Patrick Walsh, MD, a urologic surgeon at Johns Hopkins Medical Center in Baltimore, discovered that the nerves controlling erections do not pass through the prostate, as previously thought, but are instead situated alongside the prostate. By 1984, Walsh had developed a new technique nerve-sparing radical prostatectomy that enabled him to preserve sexual function in a percentage of his prostate cancer patients.
     Results vary while many urologists now use nerve-sparing procedures, the results vary widely depending upon the skill of the surgeon, the age of the patient and other factors, according to published reports. In studies of patients undergoing such procedures, reported rates of success in preserving sexual function have ranged from 11 to 86 percent.
     A recent study from the University of Toronto claims that with use of the CaverMap Surgical Aid, doctors may get consistently good results in nerve preservation. In the study, described in the October 1998 issue of the GOLD Journal of Urology, Toronto researchers say they preserved potency in 16 out of 17 men.

Mapping procedure
The device consists of a white surgical wand with a flexible tip that delivers an electrical stimulus of up to 20 milliamps to the tissue around the prostate. A separate, fluid-filled ring that is placed around the penis can detect even the slightest erectile swelling in response to the stimulus. The physician typically begins locating the critical nerves by placing the tip of the wand at the end of the prostate, then moving it to the middle and finally to the base of the organ. This effectively produces a map of the key nerves involved in erectile function, Brooks said. The patient, under general anesthetic, feels nothing, he said.
     After the prostate has been removed, the physician can retest the nerves to confirm that they have been spared, Brooks said. Most men take months to regain erectile function after any prostate surgery because of the trauma to the region, he noted. Use of the nerve-finding device adds about an hour to the standard surgical procedure, for a total of about three hours, Brooks said. Studies by others have shown that cure rates for localized prostate cancer are the same whether doctors perform a traditional surgery or use the nerve-sparing approach, he said.

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November 1, 1998. ModifiedDecember 26, 1998

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