New nerve stim approach may provide option in OAB

April 1, 2007

Dorsal genital nerve stimulation using a minimally invasive, pre-pubic approach appears to reduce the symptoms of overactive bladder and is well tolerated by patients, according to results of a prospective, multicenter feasibility study.

Key Points

Christchurch, New Zealand-Dorsal genital nerve stimulation using a minimally invasive, pre-pubic approach appears to reduce the symptoms of overactive bladder and is well tolerated by patients, according to results of a prospective, multicenter feasibility study.

The 21 women in the study tolerated both the placement of stimulating electrodes and the sensation of stimulation. Positive effects from stimulation appeared during the 7-day treatment period.

Women in the study averaged 52.7 years of age, with an average duration of incontinence of 6 years. Placement of electrodes required only 5 to 10 minutes for each patient and was performed under local anesthesia. Test stimulation was used to confirm correct electrode placement.

Subjects underwent a 5-day anticholinergic washout period, after which researchers obtained baseline data, including a 3-day bladder diary and 24-hour pad test.

"One of our objectives was to determine if there were any acute effects of stimulation on urodynamic parameters or on the pudendal-anal reflex to develop a screening technique for identifying candidates for permanent implantation," Dr. Goldman said.

Good results for most

Pad weight was reduced by 50% or more in 13 of 17 subjects for whom data were available, while eight patients reported a 50% or greater reduction in leaks. Also encouraging was the fact that 81% of patients who reported severe urgency at baseline had a 50% or greater improvement.

"Prior to the human studies, we could not predict whether an electrode could be effectively placed near the dorsal genital nerves," Dr. Goldman said during the International Continence Society annual meeting. "We had to conduct a series of preclinical cadaver studies to identify the course of the dorsal genital nerves and to define the optimal implantation technique."

Seven subjects experienced what the authors described as "mild adverse events," including skin irritation and bruising around the electrode exit site. Interestingly, relief from symptoms appeared to continue for some subjects during a 3-day post-treatment period.

The stimulation technique used by Dr. Goldman and colleagues differs from that currently used to relieve symptoms of urge incontinence. Sacral nerve stimulation, for example, is applied unilaterally to the S3 sacral nerve, which contains both motor and sensory fibers of various sizes. Nonspecific stimulation of the pudendal nerve in the perineum is also being studied.

The Goldman group's approach, on the other hand, delivers bilateral, specific stimulation to the dorsal genital nerves-a "pure sensory nerve," as Dr. Goldman puts it-which has an inhibitory effect on the bladder.