IC patients prefer pudendal target for neuromodulation

October 15, 2005

San Antonio--Targeting the pudendal nerve directly with neuromodulation rather than the third sacral nerve root might produce better results for patients with interstitial cystitis.

San Antonio--Targeting the pudendal nerve directly with neuromodulation rather than the third sacral nerve root might produce better results for patients with interstitial cystitis.

Although objective data did not bear this out, patient preference did in a small, single-blinded, randomized crossover trial presented here at the AUA annual meeting. Researchers at William Beaumont Hospital in Royal Oak, MI, tested both types of stimulation using two electrodes with InterStim (Medtronic, Minneapolis) instead of the usual one.

Twenty-two patients who had refractory IC and who chose neuromodulation treatment had a quadripolar, tined lead placed at S3 and a second lead placed at the pudendal nerve. Both leads were positioned using a posterior approach with fluoroscopic guidance. Test stimulations confirmed activity in both locations, and plain radiographs confirmed placement of the leads.

Each lead was tested on every patient for 7 days without the patient knowing which lead was activated. To assess results, researchers had patients maintain voiding diaries, answer symptom questionnaires, and rate their improvement. After the crossover testing phase, patients chose which lead they wanted to be used with the permanently implanted pulse generator.

Of the 22 patients, 17 (77%) showed a response (50% improvement in symptoms) and had the pulse generator implanted. Four of the 17 (23.5%) chose the sacral lead; 13 (76.5%) preferred the pudendal lead. The order in which the leads were tested had no impact on the final lead placement, noted David Konstandt, MD, chief urology resident at William Beaumont Hospital, who worked on the study with Kenneth Peters, MD, and colleagues.

Significant improvement

Most subjective data from patients about symptoms and improvement were statistically significant in favor of pudendal nerve stimulation. Patients reported a mean 59% improvement with pudendal nerve stimulation versus a mean 44% improvement with sacral nerve stimulation. On a seven-point scale ranging from markedly worse to markedly better, pudendal nerve stimulation was superior to sacral nerve stimulation for controlling urinary frequency and urgency. However, there were no differences between the two methods in vaginal pain, pelvic pain, sexual function, or incontinence.

The number of voids per day, the mean voided volume, and the smallest voided volume were significantly improved over baseline, but they were not significantly different between sacral and pudendal nerve stimulation.The team found no pretreatment characteristic that could determine which patients would do better with which lead.

"I honestly think that if you did a head-to-head trial and randomized 50 patients to sacral and 50 patients to pudendal and they didn't get to test each one within themselves, you'd have a very similar implant rate and response rate. I think it's only because patients were able to experience both that there was a difference in choosing pudendal over sacral," Dr. Konstandt said.

Anatomy might offer an explanation for the differences. Traditionally, sacral nerve stimulation is done unilaterally at the S3 nerve root. The pudendal nerve, however, usually originates from nerve roots at S2, S3, and S4, so the afferent stimulation to the spinal cord could pass through all three nerve roots, adding to the effectiveness of the stimulation.

A choice for patients

Dr. Konstandt said he looks toward a future when all urologists implanting neuromodulators could offer this choice to their patients, and could even offer the pudendal option to patients for whom sacral nerve stimulation has failed.

Is this technique ready for prime time?

"No," he replied. "It's ready for more clinical trials, which are being developed. Maybe, as we accrue more patients, there will be some statistical significance in terms of objective data between sacral and pudendal."

"Neuromodulation is an evolving area," Kristene Whitmore, MD, chief of urology at Graduate Hospital in Philadelphia, told Urology Times. "It's really going to continue to change."

She cited other studies on new approaches to neuromodulation, such as bilateral (rather than unilateral) stimulation that also captures the sacral nerve roots from S2 to S5 and a new, small device that can be placed at the pudendal nerve and charged with an external device. Even pelvic floor physical therapy and acupuncture are neuromodulation techniques, Dr. Whitmore pointed out, adding that urologists can expect many new applications and improvements in the treatment of IC.