Pudendal EA for LUTS

Stimulated by Chen et al 2021.[1]

Photo by Pixabay on Pexels.com

EA – electroacupuncture
LUTD – lower urinary tract dysfunction
LUTS – lower urinary tract symptoms
SNM – sacral neuromodulation
IPG – implantable pulse generator
EPNS – electrical pudendal nerve stimulation

key to acronyms

This week I am choosing a case report to highlight because it nicely illustrates the overlap between EA and more sophisticated and expensive forms of neuromodulation used for LUTD.

This report comes from Hangzhou, which I have mentioned recently for the first time on this blog (see ST36 EA and antitumour effects). It describes a 51-year-old man with quite significant lower urinary tract symptoms (LUTS). As well as having urgency and frequency, he also had intermittent urinary retention, for which he would self-catheterise 1 to 3 times per week. His daytime frequency was 12 to 14 times, and he had 4 to 5 episodes of nocturia per night.

Hangzhou is on the Qiantang river, which opens into the Hangzhou bay to the south of Shanghai and north of Ningbo

He had numerous investigations, most of which were normal. His prostate was of normal size, and MRI was normal. Urodynamics demonstrated an underactive detrusor but no outflow obstruction.

He was started on tamsulosin and baclofen, but these were ineffective, and he was offered sacral neuromodulation (SNM). This starts with placement of a permanent lead through the S3 foramina from the posterior aspect, so that the end lies close to the anterior ramus of the S3 spinal nerve. This lead is connected to a temporary lead that is tunnelled laterally so that it comes out near the iliac crest and it can be attached to an external stimulator. If the stimulation proves effective, the second stage is to implant a stimulator in the ipsilateral buttock and replace the temporary lead with a permanent one. These are expensive devices, and the total price tag rapidly runs to over £20k per patient. This figure then just increases over time with the requirement for battery changes or treatment of complications.

SNM costs at least £20k per patient

In this case the device was offered as part of a trial, so there was no cost to the patient. The patient reported mild improvement only at stage 1 but proceeded to have an implantable pulse generator (IPG) sited (stage II) anyway. There was no further improvement after implantation and after 3 months any positive effect was lost, and he felt irritable when the IPG was turned on. He also complained of insomnia and depression.

Approximately 1 year later the patient presented to the authors’ clinic and was offered bilateral electrical pudendal nerve stimulation (EPNS). This involved a pair of needles (0.40x100mm) being inserted on each side of the sacrococcygeal joint (probably near BL54) and another pair at the level of the tip of the coccyx (sounds like BL35). The upper needles were inserted perpendicularly to a depth of 80mm and the lower needles were inserted obliquely in a lateral direction to about 90mm.

I have been intrigued by the anatomical aspects of attempting direct EA stimulation of the pudendal nerve since first coming across the technique in Porto Alegre care of my friends in the GEANF. Later I was approached by a colleague from Portugal (Mariana) who had modified the GEANF approach she had learned to avoid the problem of motor point stimulation of gluteus maximus, and I helped publish her findings in Acupuncture in Medicine.[2] It was around the same time that I first saw a 4 needle EA protocol (BL33 and BL35 bilaterally) used in a large clinical trial of stress incontinence (see EA for SUI),[3] and I suspected that the approach targeted the pudendal nerve as well as the S3 nerve root.

I resurrected the diagram I had created for the paper with Mariana (see Sacral needling for the original) and placed the needles according to the description in this case report on EPNS to try to work out exactly where the needles went.

Edited version of the image used in Oliveira 2018,[2] illustrating the position of the needle placement described in Chen et al 2021.[1] The gluteus maximus muscle and the sacrotuberous ligament are faded so that the deeper structures can be seen. Anatomical image prior to editing is reproduced with permission. Primal Pictures. All rights reserved. Primal Pictures, a division of Informa, UK. www.primalpictures.com http://www.anatomy.tv/

The upper needle is at S4 level, which will be below the piriformis and the sciatic nerve and its roots. It looks as though it could get stuck in the sacrotuberous ligament, so I guess the approach goes just above this structure. With sufficient depth the needle reaches the sacrospinous ligament, and the pudendal nerve runs along the top of this ligament before winding around it to enter Alcock’s canal along with the pudendal vessels. The lower needle appears to run below the sacral attachment of the sacrotuberous ligament almost in line with the sacrospinous ligament. Whilst I have made it look straightforward in the diagram, when inserting a needle so deeply, the slightest change in angulation could lead to a big difference in where the tip ends up. Presumably the angulation was adjusted until the patient felt a referred sensation in the pudendal nerve distribution, in this case the authors mention sensation referred to the urethra.

In this case we are told that the EA was applied daily for 60 minutes at 2Hz and moderate intensity. They mention 25–35mA, but it sounds like they are missing a decimal point in there as 2.5–3.5mA on the devices I use would be moderately strong for most patients. I just looked up the device they used online, and it doesn’t appear to have a readout in milliamps so it could be an error of interpretation on the analogue intensity dial.

The patient improved, and after 4 weeks of daily weekday treatment he stopped using the IPG. After 8 weeks he was discharged home, and was very good for 2 weeks, but started developing some difficulties with voiding by week 3, so he had turned on his IPG again.

I note that this group are currently running a trial of EPNS compared with more standard EA in urinary incontinence after stroke.[4]

When I started out on this blog, I was expecting to comment that EA should be tried before SNM in most cases of LUTS due to LUTD, but I’m not sure this case illustrates that point very well. This EPNS treatment involved an 8 week stay as an inpatient, and in the end, the patient turned on his IPG on again after just 2 weeks.

Certainly, we should be trying less invasive approaches before considering EPNS or SNM. I would probably start with pairs of needles at SP6 bilaterally, and if that worked, I would teach the patient to do it themselves 2 or 3 times a week. I don’t think I will ever see daily EPNS performed in hospitals in the west, but I continue to be interested by the anatomical technicalities of safely reaching the pudendal nerve with an acupuncture needle without imaging. In terms of safety I should mention that we are most interested in avoiding the rectum, and it is very close to the points at S4 and below, hence the angulation of the lower needles in a lateral direction. I would also use a slight outward angulation at BL54 (S4) if I was using a 100mm needle.


1          Chen S, Wang S, Gao Y, et al. Bilateral electrical pudendal nerve stimulation as additional therapy for lower urinary tract dysfunction when stage II sacral neuromodulator fails: a case report. BMC Urol 2021;21:37. doi:10.1186/s12894-021-00808-5

2          Oliveira e Lemos M, Cummings M. An Alternative Approach to Pudendal Nerve Stimulation. Acupunct Med 2018;36:423–4. doi:10.1136/acupmed-2018-011751

3          Liu Z, Liu Y, Xu H, et al. Effect of Electroacupuncture on Urinary Leakage Among Women With Stress Urinary Incontinence: A Randomized Clinical Trial. JAMA 2017;317:2493–501. doi:10.1001/jama.2017.7220

4          Chen S, Wang S, Xuan L, et al. Comparison of efficacy and safety between electroacupuncture at “four sacral points” and conventional electroacupuncture for the treatment of urinary incontinence after stroke: study protocol for a randomised controlled trial. BMJ Open 2018;8:e021783. doi:10.1136/bmjopen-2018-021783

Declaration of interests MC