Wang Si-you

Shanghai Research Institute of Acupuncture and Meridian, Shanghai 200030, China

Electroacupuncture Pudendal Nerve Stimulation and Its Application

Wang Si-you

Shanghai Research Institute of Acupuncture and Meridian, Shanghai 200030, China

Voiding dysfunction, such as urge-frequency syndrome, urge incontinence, stress incontinence and unobstructive urinary retention, is often refractory to pharmacotherapy. Electrical neuromodulation has proved to be beneficial for these situations. Electroacupuncture pudendal nerve stimulation (EPNS), as one therapy of electrical neuromodulation, is beneficial for voiding dysfunction. The performance and application of EPNS will be introduced in this article.

Acupuncture Therapy; Long Needle Therapy; Electroacupuncture; Pudendal Nerve Stimulation; Voiding Dysfunction

1 Introduction

Voiding dysfunction, such as urge-frequency syndrome, urge incontinence, stress incontinence and unobstructive urinary retention, is often refractory to pharmacotherapy. Electrical neuromodulation has proved to be beneficial in these situations. The electrical neuromodulation therapies include transvaginal or transanal electrical stimulation (TES), percutaneous tibial nerve stimulation (PTNS), sacral neuromodulation (SNM) and pudendal neuromodulation (PNM)[1].

TES is easily applicable but it is sometimes intolerable for many patients due to discomfort, mucosal injury and high intensity stimulation for acceptable outcome[2]. SNM with the interstim device 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[3]and at least 20% of the patients initially tested do not respond to a test procedure[4]. Its disadvantages include invasiveness of the procedure, the high cost of treatment, the high surgical revision rate, device replacement required when battery runs out and adverse events (pain and infection)[1,5]. Because pudendal nerve (PN) afferents are particularly important for the inhibitory effect on the voiding reflex and SNM only excites part of PN afferents, direct PN stimulation may be more effective[1]. PNM with the interstim device or the bion device (belonging to selective pudendal nerve stimulation) can be used to treat voiding dysfunction refractory to SNM[1,6], but this therapy also has the disadvantages similar to those of SNM[1,7]. PTNS with needle electrodes is minimally invasive, demonstrates efficacy, and is easily applicable and well tolerated[8], but PTNS effects diminish over time after the end of treatment[9,10]. PTNS, SNM and PNM are not used for stress incontinence. TES will result in the contraction of pelvic floor muscles (PFMs) by indirect nerve stimulation[11]and mainly by polysynaptic reflex responses[12]. Therefore, TES can also be used to treat stress incontinence. But the indirect stimulation and reflexive contraction may be the reason why the effect of TESon stress incontinence is not as good as that of pelvic floor muscle training (PFMT) when performed correctly[13]. PFMT improves the structural support of the pelvis[14]and is a commonly used form of conservative treatment for stress incontinence[15]. However, many patients, especially women have difficulty identifying and isolating their PFMs and are unable to perform the exercise effectively. Furthermore, patients who can identify the PFM often find that the required daily exercise routine is burdensome. Thus, the primary disadvantage of PFMT is lack of long-term patient compliance[11]. By combining the advantages of PNM (better effect), PTNS (minimally invasive, easily applicable and well tolerated), TES (passive PFM contraction and good compliance) and PFMT (better effect on stress incontinence) and incorporating the technique of deep insertion of long acupuncture needles, we developed electroacupuncture pudendal nerve stimulation or electrical pudendal nerve stimulation (EPNS)[16]. EPNS was used to treat urgefrequency syndrome, stress incontinence, urge incontinence and unobstructive urinary retention, and good therapeutic effects were obtained[16-18].

2 Performance of EPNS

EPNS is performed as follows. The patient takes a prone position. Four sacral points (Fig.1-2) are selected for deep insertion of long acupuncture needles (Suzhou Shenlong Medical Apparatus Factory, China). The two upper points are located about 1 cm bilateral to the sacrococcygeal joint (Fig.1). On the upper points, a needle of 0.40 mm in diameter and 100 mm in length is inserted perpendicularly to a depth of 80-90 mm to produce a sensation referred to the urethra or the anus by stimulating the main trunk of the pudendal nerve (Fig.2-3). The locations of the two lower points are about 1 cm bilateral to the tip of the coccyx (Fig.1). On the lower points, a needle of 0.40 mm in diameter and 100 mm or 125 mm in length was inserted obliquely towards the ischiorectal fossa to a depth of 90-110 mm to produce a sensation referred to the urethra by stimulating the perineal nerve (the perineal branch of the pudendal nerve), (Fig.2-4). After the sensation referred to the above regions is produced, each of two pairs of electrodes from a G6805-2 Multi-purpose Health Device (Shanghai Medical Instruments High-Techno, China) is connected with the two ipsilaterally inserted needles with the anode to the upper needle and the cathode to the lower needle. The device is set to produce electrical stimulation (biphasic, 2 ms pulse duration) at a frequency of 2.0-2.5 Hz and a moderate intensity (25-35 mA) for urge-frequency syndrome, urge incontinence and unobstructive urinary retention or at a frequency of 2.5 Hz and an intensity (45-55 mA) as high as the patient can tolerate without discomfort for stress incontinence. The electrostimulation is set for 60 min each time. PFM contraction around the urethra (often comfortable) must be kept during the entire electrostimulation.

Fig.1 Four sacral points

Fig.2 Four sacral points with inserted needles

Fig.3 Needle insertion directions

3 Interpretation

The site about 1 cm bilateral to the sacrococcygeal joint is close to the main trunk of PN (Fig.1), so the body surface over it (the upper point) is selected for deep perpendicular insertion of a long needle (Fig.2-3). Because PN contains sensory fibers innervating the external genitalia and anus, the sensation is referred to the urethra or anus during needle insertion. In the ischiorectal fossa, PN branches into the perineal nerve innervating the PFM (including the sphincter urethra, compressor urethra and urethrovaginal sphincter, namely deep transverse perineal muscles), part of the levator ani muscle, the superficial perineal muscles and the skin of the scrotum/labium majus, and the dorsal nerve of the penis/clitoris innervating the skin of the penile/clitoral shaft. Therefore, the sensation is only referred to the urethra when a long needle is inserted beside the tip of the coccyx laterally towards the ischiorectal fossa to make the needle tip reach the perineal nerve (Fig.2-4), and rhythmic peri-urethral PFM contractions (often comfortable) are felt when moderate- or high-intensity electrical stimulation is provided.

As shown in Fig.4, 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[19]. 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, contract the PFM and stimulate PFMT[16]. The simultaneous records have also showed that the correct position of the (not isolated) needle tip is very important during the performance of EPNS (Fig.5-6)[16]. It can be seen in Fig.5-6 that when EPNS is performed correctly, simultaneous recordings show: ① B-mode cranio-caudal PFM movements; ②M-mode PFM movement curves (Fig.5; amplitude: about 1 mm); ③ a sawtooth curve of VP changes [green a–b period in Fig.5, amplitude: (2.61±1.29) cm H2O); ④ PFM myoelectric waves [red a–b period in Fig.5, amplitude: (23.9±25.3) μV]. If during the EPNS process the two lower needles were gradually drawn back 1-2 cm away from the original positions, then the above ultrasonographic PFM movements and VP changes disappeared (Fig.6; green b–c period in Fig.5-6). If the positions of the needle tips were restored to their original settings, the above ultrasonographic PFM movements and VP changes returned to the originals also (green c–d period in Fig.6). The results indicate that only if the needle tip is very close to PN, can PN be excited and the PFM contract most effectively.

Fig.4 CT transverse plane at the coccygeal apex with the lower needle tip in the ischiorectal fossa (adjacent to the pudendal nerve at Alcock's canal)

Fig.5 Simultaneous measurements (including early record) (V=vagina, m=M-mode line, M=M-mode image, t=the time corresponding to the left image)

Fig.6 Simultaneous measurements (including late record) (V=vagina, m=M-mode line, M=M-mode image, t=the time corresponding to the left image)

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R246.1

A

Date: January 15, 2013

Author: Wang Si-you, professor. E-mail: wangsiyou1234@163.com