The Long-term Efficacy of Electrical Pudendal Nerve Stimulation for the Urgency-Frequency Syndrome in Women

Urgency-frequency syndrome (UFS) is often refractory to pharmacotherapy. Electrical neuromodulation has proved to be valuable in this situation. The electrical neuromodulation therapies include transvaginal electrical stimulation (TES), percutaneous tibial nerve stimulation (PTNS), sacral nerve stimulation (SNS) and pudendal nerve stimulation (PNS). Their effects can be explained by modulation of reflex pathways at spinal and supraspinal levels.

TES is easily applicable but it is sometimes intolerable for many patients due to discomfort, mucosal injury and high intensity stimulation for acceptable outcome. SNS differs from TES by its continuous stimulation and close nerve contact. It has a high rate of success, but symptoms appear to recur almost immediately after discontinuation of the stimulation and at least 20% of the patients initially tested do not respond to a test procedure. Its disadvantages included invasiveness of the procedure, the high cost of treatment, the high surgical revision rate, device replacement and adverse events. Because pudendal nerve (PN) afferents are particularly important for the inhibitory effect on the voiding reflex and SNS only excites part of PN afferents, direct PN stimulation may be more effective. PNS can be used to treat UFS refractory to SNS, but this therapy also has the disadvantages similar to those of SNS. PTNS is minimally invasive, demonstrates efficacy, and is easily applicable and well tolerated, but the results of chronic PTNS treatment are unknown in initially successful patients and PTNS effects diminish over time.

By combining the advantages of PNS and PTNS and incorporating the technique of deep insertion of long acupuncture needles, we developed electrical pudendal nerve stimulation (EPNS). In EPNS, long acupuncture needles of 0.40 Х 100 or 125 mm were deeply inserted into four sacral points and electrified to stimulate the pudendal nerves. CT transverse plane at the coccygeal apex has showed that the position of the lower needle tip is similar to where (adjacent to PN at Alcock's canal) the Bion device is implanted for chronic PN stimulation. Besides the radiographic evidence, simultaneous records of perineal ultrasonographic PFM contraction, vaginal pressure and pelvic floor surface electromyogram in our previous study have proved that EPNS can exactly excite PN. Our previous study has also proved that EPNS has a good post-treatment effect on UFS in women. The purpose of the present study is to show the long-term efficacy of EPNS for UFS in women.