Pudendal nerve stimulation shows effect in OAB

Montreal-Urinary incontinence caused by neurogenic overactive bladder can be successfully treated with a novel system of pudendal nerve stimulation, according to a small Italian study presented at the annual meeting of the International Continence Society here.

The minimally invasive percutaneous procedure, known as chronic pudendal nerve stimulation (CPNS), appears to be both safe and effective. In addition, it may have a positive effect on erectile and bowel dysfunction, the researchers reported.

The procedure involves the implantation of a tined lead close to the pudendal nerve under neurophysiologic guidance, explained Michele Spinelli, MD, principal investigator and a physician at the spinal unit of Niguarda Hospital in Milan.

The CPNS method, which the researchers began using in June 2002, involves measuring pudendal nerve terminal motor latency responses and compound muscle action potentials at the external anal sphincter. The best response generated is regarded as the reference potential response. Patients then have leads implanted surgically and are anesthetized locally in the sacral area where the leads are placed. A pulse generator is then implanted.

"It is important that this is done under neurophysiological guidance," Dr. Spinelli emphasized.

Indeed, neurophysiologic monitoring verifies the consistency between the recorded trace and the reference potential response and permits researchers to check responses to sacral area dysfunctions.

Improvement in continence

Twenty of the 36 patients first underwent invasive sacral neuromodulation staged implant with tined lead, while 16 patients underwent CPNS using the same system. Of the 20 who first underwent sacral neuromodulation before CPNS, nine had worsening of symptoms, and 11 had no success at all.

Patients completed neurophysiologic and urodynamic evaluation at baseline and follow-up. They completed a bowel and voiding diary for 7 days, and half the male subjects completed the International Index of Erectile Function (IIEF).

The patients' average number of urinary incontinence episodes fell from seven to 2.6 during the study's screening phase, which the authors attributed to CPNS. The majority of patients with urge incontinence (29) became continent during the screening phase. An additional two patients reduced their daily incontinence episodes dramatically from nine to one, and one reduced the number of episodes by half. Four patients experienced no improvement in their incontinence symptoms.

At a mean follow-up of 21 months, 17 were dry using self-catheterization for voiding, two used catheterization twice a day, and 15 patients voided without a catheter.

Urodynamic assessment demonstrated objective improvement. Among patients with urge incontinence, the maximum cystometric capacity rose from 153.3 to 33.1 mL. The pressure at maximum cystometric capacity fell from 66 to 36 cmH₂O. One patient exhibited symptoms of retention and showed no improvement in either urodynamic or clinical values.

"It is very simple for the clinician to use," Dr. Spinelli said. "The challenge is to find the best electrical parameters of stimulation since the patients are starting from different situations at baseline."

Erectile, bowel function

The procedure not only has an effect on bladder function, but also on other sacral area functions, such as erection and bowel function, Dr. Spinelli pointed out.

"If you stimulate this target [sacral area], it has an effect on other areas," he said.

The seven men who completed the IIEF reported an increase in the mean percentage on the IIEF from 32% to 79%. Concomitant with this rise was a drop in their use of oral drugs to treat erectile dysfunction.

A total of 15 patients had constipation at baseline, and 11 indicated normal bowel function subsequent to undergoing CPNS, with an increase in the number of weekly evacuations from 2.5 to seven, as well a s a decrease in straining and laxative use. One patient who had fecal incontinence became continent.

Researchers will embark on a larger study involving multiple centers to confirm their results, Dr. Spinelli said.