Although the usefulness of percutaneous tibial nerve stimulation (PTNS) therapy to overactive bladder (OAB) have reported to be effective, it was invasive because a fine needle electrode must be inserted for the electrical neuromodulation. We have developed silver spike point (SSP), a non-invasive (painless) electrode without inserting a needle for the stimulation (Figure 1). This method had already been applied to the treatment of anesthesiology and so on (1, 2, 3). The aim of this study was to investigate the safety and efficacy of transcutaneous tibial nerve stimulation (TTNS) therapy using SSP electrodes in refractory OAB.

Patients with refractory overactive bladder who could not be cured by drug therapy were included. This study was a prospective study, and the patient underwent TTNS therapy using silver spike point electrodes twice a week for 6 weeks (12 times in total). One treatment session was 30 minutes. The stimulation sites were SP6 (Sanyinjiao) point of both legs, and the silver spike point electrode was placed at each site (Figure 2). The silver spike point electrode was made of silver plated brass that can stimulate nerves without inserting a needle. The tip of silver spike point electrode stretched skin and lowers electric resistance. As a result, electric current was concentrated on the tip, and electric stimulation became possible. The pulse wave was a biphasic symmetrical wave, the pulse width was 50 μs, and the frequency was from 2 to 16 Hz. The intensity was maximum tolerable level. The primary endpoint was the change in total score of overactive bladder symptom score. Secondary endpoints were subjective therapeutic effectiveness, change in the total score of the International Consultation on Incontinence Questionnaire-Short Form, the number of daytime voids, the number of nighttime voids, the frequency of urgency episodes, the frequency of urinary incontinence episodes, the maximum voided volume and the average voided volume in frequency-volume chart. These were evaluated before and at 4 weeks after the treatment.

Eighteen cases (13 males and 5 females) were included in this study. The age was 62.7 ± 18.7 years old (8 to 83 years old). There was no adverse event. The total score of overactive bladder symptom score was significantly decreased from 9.6 ± 2.0 points before treatment to 7.3 ± 3.0 points after treatment (P = 0.0039). Most of the patients (66.7 %) were satisfied feeling the effect. The total score of International Consultation on Incontinence Questionnaire-Short Form was significantly reduced from 10.1 ± 5.1 points before treatment to 5.1 ± 6.9 points after treatment (P = 0.0021). In frequency-volume chart, the urinary frequency, the frequency of urgency episodes and the frequency of urinary incontinence episodes were 11.1 ± 2.8, 3.2 ± 3.6 and 1.5 ± 1.8 times ,before the treatment, and 10.5 ± 2.8, 2.0 ± 2.8 and 1.0 ± 1.7 times, respectively, after the treatment (P = 0.3448, 0.0234 and 0.1387, respectively). The maximum voided volume and the average voided volume were 271.9 ± 116.1 and 152.0 ± 70.1 ml before treatment and 307.3 ± 170.9 and 160.9 ± 74.7 ml after treatment (P = 0.4199 and 0.6023), respectively.

The TTNS therapy with silver spike point electrodes in refractory overactive bladder was safe and effective. Although there was a significant difference in the frequency of urgency episodes, there was no significant difference in the urinary frequency and the frequency of urinary incontinence episodes in frequency-volume chart, probably due to the small number of cases.

This study was the first to evaluate the safety and effectiveness of TTNS therapy with silver spike point electrodes in refractory overactive bladder. The benefits of this method seemed to be that it was painless and did not cause adverse events such as infections.
The TTNS therapy with silver spike point electrodes was found effective and safe.

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