Stimulated by Li et al 2025.[1]
EPNS – electrical pudendal nerve stimulation
PPUI – post-prostatectomy urinary incontinence
EA – electroacupuncture
IF – impact factor
APC – author processing chanrge
RCT – randomised controlled trial
PFMT – pelvic floor muscle training
TES – transrectal electrical stimulation
RMS – root mean squared– key to acronyms
I was immediately attracted to the title of this paper because it started with EPNS, although I am not a fan of all the different acronyms surrounding EA-like interventions. In this case it is simply a form of EA in the territory of the pudendal nerve (more on this later).
It is a retrospective cohort study, but smaller (n=389) than the ones we are used to from Taiwan and Korea (see Retrospective cohorts). It is published the open access journal Scientific Reports (IF 3.9), which is from the Nature Portfolio and claims to be the 3rd most cited journal in the world, with more than 834k citations in 2024. It has an APC of £2190, which is about £1k less than our equivalent I was surprised to learn.
A couple of months ago I highlighted an RCT on PPUI, although I used a different acronym that time (see EA for post-RARP UI).[3] There was only a small percentage of robotic assistance in this one, so I stuck with PPUI. The paper actually uses PPI as the acronym, but that is just going to get confusing when we have seen the more familiar use of that acronym very recently on here (see Pneumonia risk in stroke patients on PPIs).
In this retrospective cohort EPNS (EA) was compared with the more conventional treatment approach of PFMT plus TES. From the description in the paper, the PFMT was performed with the TES probe in place and presumably giving EMG feedback, and then the TES was performed. There was 20 minutes of each, giving a total treatment time of 40 minutes. This was performed 3 times a week for 8 weeks.
The patients receiving EPNS were told not to perform any PFMT. Two points were used on each side of the coccyx. The upper one at the level of the sacrococcygeal joint and the lower one at the level of the tip of the coccyx. In both cases the points were approximately 1cm lateral to the bony landmark. At the upper point a needle of 0.40x100mm was inserted perpendicularly to a depth of 80-90mm until the patient felt a sensation referred to the anus. The lower point was needled in an anteriolateral direction towards the ischeorectal fossa until a sensation was felt in the perineum at the root of the penis. The depth was said to be 90-110mm, so a 120mm needle was used in some cases.
My guess is that the upper needle must go beneath the medial attachments of the sacrotuberous and sacrospinous ligaments because it is very difficult to needle through these ligaments. They attach to the upper part of the coccyx below the sacrococcygeal joint, so perpendicular insertion at the level of the joint would aim directly for the ligaments. If you start at the level of the joint and then angle beneath the ligaments, the good news is that the needle is less likely to hit the rectum, but it will certainly be in or close to the levator ani muscle.
The lower needle is angled laterally, which is good, because that angles slightly away from the rectum. I guess that the needle track goes medial to the sacrotuberous ligament and the sensation generated in the perineum presumably indicates stimulation of the pudendal nerve.
The stimulation was performed at 2.5Hz with a biphasic charge-balanced pulse of 2ms for 60 minutes. The intensity was adjusted to achieve visible contraction of the pelvic floor (perineal lift and or anal wink). They suggest the average intensity was 45-55mA, but I strongly suspect that they have missed out a decimal point, so I emailed the lead author to check. He responded with a lot of supplementary information and images, which I will share on the webinar. The output was a peak measurement and he guesses that the RMS average would be ~1mA.
On scanning some references from this paper I came across images that I recognised. Further digging and searching for EPNS on this blog and I realised that I have already come across this 4 point EA technique in 2021 (see Pudendal EA for LUTS). I also found a paper that we had published in Acupuncture in Medicine by the same team as that highlighted previously.[4,5] The same group had published a protocol for a trial comparing EPNS with more conventional EA (abdominal points) for urinary incontinence after stroke.[6] I contacted the lead author to ask about the results of this trial and got a rapid reply and a further paper, which I had not seen since it was not published in a Medline-listed journal.[7] Unfortunately, the results of the trial comparing EPNS with EA was published in Chinese language journals, so I asked for a brief description of the results, and the lead author told me that the EPNS was superior to abdominal EA.
Another relevant blog is Sacral needling 2020 – this mostly revoles around needling into the sacral foramina. I think this would have been a better comparison than abdominal EA for the 4 point protocol described above.
I better mention the results in the current paper before signing off here. In short, the EPNS protocol appeared to be substantially better than the PFMT plus TES, but do remember that this is a retrospective cohort (observational research).
I have just watched the webinar (14th Apr 2021) linked to the blog post from 12th April 2021 (Pudendal EA for LUTS). I see that I go into quite a lot of detail on the pelvic anatomy. Mostly I think it is ok, but I have a slightly different perspective after reading this latest paper and so I have made further modifications to the image above and I will explain further on the webinar this Wednesday.
References
1 Li T, Wang S, Chen Q, et al. Electrical pudendal nerve stimulation versus pelvic floor muscle training with transrectal electrical stimulation for post-radical prostatectomy incontinence: a cohort study. Sci Rep. 2025;15:41603. doi: 10.1038/s41598-025-25567-3
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 Niu J, Wang Y, Wang Y, et al. Electroacupuncture in Patients With Early Urinary Incontinence After Radical Prostatectomy: A Randomized Clinical Trial. JAMA Netw Open. 2025;8:e2534491. doi: 10.1001/jamanetworkopen.2025.34491
4 Chen S, Wang S, Xuan L, et al. Sacral electroacupuncture as a treatment for urge urinary incontinence: a prospective case series. Acupunct Med. 2021;39:522–8. doi: 10.1177/0964528420968846
5 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
6 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
7 Chen Y, Jin X, Hong Q, et al. Electrical Pudendal Nerve Stimulation for Post-Radical Prostatectomy Urinary Incontinence: A Prospective Study. Am J Mens Health. 2025;19:15579883251352657. doi: 10.1177/15579883251352657
The BMAS Blog 
You must be logged in to post a comment.