Pudendal Neuralgia Treatment By Injections And Surgery: Did We Help Patients?

Methods

  This is a retrospective study of prospectively collected data from records of 169 patients who received treatment for pudendal neuralgia in the period from June 2006 till May 2018 in a private medical centre (Humanitas San Pio X) in Milan/Italy.

Nantes criteria for PNa were applied on patients to aid in the diagnosis including pudendal nerve blocks and also, neurophysiologic studies. Diagnostic pudendal blocks were performed using electrical stimulation through a needle with infiltration of Bupivacaine 0.25% 5 cc around the pudendal nerve. The diagnosis was confirmed when patients documented disappearance of pain after nerve block (positive block). For neurophysiologic investigation we used PN somatosensory evoked potential (SSEP), sacral reflex and PN motor terminal latency (PNMTL) to objectively assess integrity of pudendal nerve and degree of affection. Abnormal values were considered for latencies more than 3.5 milliseconds in PNMTL, P40, N50 and P40-N50 were evaluated with SSEP.

Perineural pudendal injections (PNPI) were offered to all patients with persistent pain after conservative treatments. PNPIs were usually achieved in a similar way to the diagnostic block injecting Bupivacaine 0.25% 5 cc and Methylprednisolone 40 ml around the pudendal nerves with two blocks, between the SS and ST ligaments and one into Alcock's canal between the obturator muscle and its fascia. When patient documented an improvement of symptoms PNPI was continued for a series of three PNPI at 4 weeks interval 0, 4, and 8. Surgery was considered for patients who met the Nantes criteria with a positive pudendal block but persistent pain after PNPI. Type and approach of surgery were selected by our surgeons according to experience. Trans-gluteal and trans-ischiorectal pudendal neurolysis were the two surgical approaches.

Trans-gluteal approach with a buttock incision at the level of ischial spine explores the ST, SS ligaments and Alcock's canal through which relieving compression on PN. Trans-ischiorectal approach was performed on a female patient through a small incision which was made in the back of the vagina and the surgeon cut the SS ligament to release the compression between the ST and SS ligaments. Also, the surgeon explored the Alcock’s canal by finger dissection and released the nerve from any tethering fascia. Visual Analogue Scale (VAS) was used to subjectively measure the responses of patients to our diagnostic and therapeutic procedures. Patients were instructed to point to the position on a line between two faces to indicate how much pain they are currently feeling. The far left face indicates "no pain" and the far right one indicates "worst pain ever." The mean time for follow up of patients was for 32.3 months (2-101) in the form of regular visits to out-patient clinic and/or contacting them by phone call. Patients with anal fissure, abscess, inflammatory bowel disease, solitary rectal ulcer, prostatitis, pelvic endometriosis, neurologic diseases, and psychiatric disorders were excluded. Approval for the conduction of the study was given by both the ethical committee of the hospital and patients. Appropriate tests were applied for statistics.

Results

 The total number of patients was 169; 118 were females and 51 males. The mean age of patients was 53.2 years (28-78). All patients were diagnosed to have PNa according to Nantes criteria; 80% had also an abnormal value at neurophysiologic investigation (SSEP and PNMTL). Fifty seven patients (33.7%) had no improvement after a series of three PNPI. Eight patients (4.7%) showed no response to the first injection of PNPI series and management had been abandoned. Six percent of patients underwent repeated courses of the three PNPI series but showed no improvement. Approximately 66.3% of patients (112) responded well to PNPI series; 20.5% (23) had a complete recovery, while 79.5% (89) had a positive temporary response. The total number of patients considered for surgery was 43 (25.4%); 17.7% (30) who showed no improvement after PNPI series but with positive block, and 7.7% (13) among the patients who showed a PNPI positive temporary response.

Forty-two patients underwent trans-gluteal pudendalneurolysis, while one patient underwent trans-ischiorectal pudendal nerve decompression surgery. After surgery 72% of patients did respond well; 13 (30%) complete recovery and 18 (42%) showed improvements (> 80% in a VAS scale). Twelve (28%) patients did not improve after surgery.

Discussion

Conservative therapy is considered as the core treatment for PNa. Prevention of certain exercises like cycling and adduction at hip joint is important along with modification of lifestyle behavior and work environment that lead to minimize sitting and so decrease pressure on pudendal nerve.

Usually the pain of PNa produces spasm in pelvic floor muscles which in turn adds more pressure on the pudendal nerve causing an increase in levels of pain. This vicious circle seems difficult to break, leading to peripheral and central sensitization of pain. Nevertheless 20%-30% of patients following lifestyle modification are predicted to improve.¹⁴once patients did not respond well to lifestyle modifications; medications can play a role in treatment such as muscle relaxants, anticonvulsants, antidepressants, and analgesics.^{15, 16}

In this study 66.3% of patients who did not respond to conservative treatments showed improvements after PNPI in accordance with the results of a study conducted by Vancaillie in 2012.¹⁷

PNPI is an imperative treatment for PNa through which local anesthetics (to block the nerve) and steroids (to minimize inflammation) are injected around the nerve and this is performed both image guided by fluoroscopy, ultrasound, or CT scan or using electrical stimulation through a needle or unguided and transvaginal in women. PNPI aims to relieve pain initially with Bupivacaine which is of rapid onset; lasting hours to a few days. But for longer term effect corticosteroids are used with onset after 1‐3 days; lasting 0‐5 weeks.Symptoms relief after PNPI may last hours, days, weeks and they may completely resolve after one, two, or three PNPI. Failure of PNPI to relieve pain may occur in case of severe nerve compression, presence of concurrent Pain Generators like Maigne syndrome or posterior ramus syndrome, and injections into ischio-anal fat rather than Alcock's canal.^{12, 18, 19}

Pudendal neurolysis surgery is usually considered after failure of conservative therapies. The length, degree, and etiology of nerve injury usually affect the outcomes from PN decompression surgery. The four approaches are the trans-gluteal, the trans-ischiorectal fossa, the perineal, and the laparoscopic. One of the most commonly used approaches is the trans-gluteal one which was described by Roger Robert in which a good visualization of the nerve is achieved. The sacrotuberous and sacrospinous ligaments are divided to relieve compression on the nerve at the ischial spine. Alcock’s canal is also explored to free the nerve from any tethered fascia.¹⁹

In the trans-ischiorectal fossa approach described by Bautrant, a small incision is made in the back of the vagina and the surgeon divides the sacrospinous ligament to release the compression between the ST and SS ligaments. Again Alcock’s canal is explored by finger dissection and the nerve is released from any fascia that might be tethering it. Bautrant showed the response to 104 decompression surgeries; with 62% (38 out of 62 patients) of totally asymptomatic patients after 1 year.²⁰

The perineal approach was described by Shafik. In this technique (Anterior approach); the patient is in the lithotomic position, a vertical para-anal incision 2 cm from anal orifice is made and the ischio-rectal fossa is entered across which the inferior rectal nerve is identified and hooked by finger and traced to PN in the pudendal canal where fasciotomy can be performed. This approach is totally blind using surgeon's finger and Shafik reported disappearance of pain in 9 women out of 11.^{21, 22}

During the laparoscopic surgery, the SS ligament is divided allowing visual access of the nerve at the ischial spine and Alcock’s canal. The nerve is released from scarring, fibrotic tissue, and swollen varicose veins. A solution of heparin may be infused into the area to prevent scar tissue formation.^{5, 23}

The outcome of surgical decompression of PN through the previously mentioned approaches is reviewed in literature and summarized in (Table I).

Table I: Comparison of the surgical outcome of PN decompression.

In the literature almost 40 % of patients who underwent decompression surgery have significant improvement in pain and 30 % have some improvement while the remaining 30 % have no change in pain. However it is considered a successful surgery if there is at least a 50% reduction in pain and symptoms.²

Our results showed 72% improvement in patients with PNa treated by surgical decompressions which were comparable to what is evident in literature. According to our study, 30% had a complete recovery and 42% showed an improvement> 80% in a VAS scale after nerve decompression.

Conclusion

  Pudendal neuralgia is an infrequent cause of chronic pelvic pain affecting the quality of patient's life. PNPI and surgical decompression of pudendal nerve can give hope to most of the patients with good results.

Acknowledgement

 Nothing to declare

References

1. Mahakkanukrauh P, Surin P, Vaidhayakarn P. Anatomical study of the pudendal nerve adjacent to the sacrospinous ligament. ClinAnat 2005; 18:200-205.
2. Mathias SD, Kuppermann M, Liberman RF, Lipschutz RC, Steege JF. Chronic pelvic pain: prevalence, health-related quality of life, and economic correlates. Obstet Gynecol. 1996;87(3):321 7.
3. Itza Santos F, Zarza-Luciáñez D, Salinas J, GómezSancha F.PudendalNerveEntrapmentsyndrome.Rev Neurol 2010; 50 (3): 157-166.

4. Martin Quan. Diagnosis and Management of Infectious Vaginitis.JABFP July-September 1990; Vol. 3 No.3.
5. Hibner M, Desai N, Robertson LJ, Nour M. Pudendal neuralgia. J Minim Invasive Gynecol. 2010;17(2):148–53.
6. Labat JJ, Riant T, Robert R, Amarenco G, Lefaucheur JP, Rigaud J. Diagnostic criteria for pudendal neuralgia by pudendal nerve entrapment (Nantes criteria). NeurourolUrodyn. 2008;27(4):306–10.
7. Marie-Louise T, Cora S, Julian M, Engelbert H, Wolfgang M. Pelvic floor symptoms in female cyclists and possible remedies: a narrative review. IntUrogynecol J. August 2015.
8. Corona R, De Cicco C, Schonman R, Verguts J, Ussia A, Koninckx PR. Tension-free Vaginal Tapes and Pelvic Nerve Neuropathy.J Minim Invasive Gynecol 2008;15(3):262-7.
9. Waseem Khoder, Douglass Hale. Pudendal Neuralgia. ObstetGynecolClin N Am41 2014; 443–452.
10. Lien KC, Morgan DM, Delancey JO, Ashton-Miller JA. Pudendal nerve stretch during vaginal birth: a 3D computer simulation.Am J ObstetGynecol2005; 192(5):1669-76.
11. Butler DS. Adverse Mechanical Tension in the Nervous System: A model for Assessment and Treatment. The Australian Joumal of Physiotherapy. 1989; Vol: 35. No.4.
12. Labat JJ, Riant T, Robert R, Amarenco G, Lefaucheur JP, Rigaud J. Diagnostic criteria for pudendal neuralgia by pudendal nerve entrapment (Nantes criteria). NeurourolUrodyn 2008; 27(4):306-10.
13. Filler AG, Haynes J, Jordan SE, Prager J, Villablanca J, Farahani K, et al. Sciatica of nondisc origin and piriformis syndrome: diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment. J Neurosurg Spine 2005;2(2):99-115.
14. Benson JT, Griffis K. Pudendal neuralgia, a severe pain syndrome. Am J Obstet Gynecol. 2005; 192(SPEC. ISS): 1663–8.
15. Hibner M, Desai N, Robertson LJ, Nour M. Pudendal neuralgia. J Minim Invasive Gynecol 2010;17(2):148-53
16. Magnus L. Nonepileptic uses of gabapentin. Epilepsia 1999;40 Suppl 6:S66-72; discussion S3-4.
17. Vancaillie T, Eggermont J, Armstrong G, Jarvis S, Liu J, Beg N. Response to pudendal nerve block in women with pudendal neuralgia. Pain Med 2012; 13:596-603.
18. Beco J, Pesce F, Siroky M, Weiss J, Antolak S. Pudendal neuropathy and its pivotal role in pelvic floor dysfunction and pain. In: ICS/IUGA conference. 2010. p. 0–12.
19. Ploteau S, Perrouin-Verbe MA, Labatt JJ, Riant T, Levesque A, Robert R. Anatomical Variants of the Pudendal Nerve Observed during a Transgluteal Surgical Approach in a Population of Patients with Pudendal Neuralgia. Pain Physician 2017; 20:E137-E143.
20. Bautrant E, de Bisschop E, Vaini-Elies V, Massonnat J, Aleman 1, Buntinx J, et al. [Modern algorithm for treating pudendal neuralgia: 212 cases and 104 decompressions]. J GynecolObstetBiolReprod (Paris). 2003 Dec; 32(8 Pt 1):705-12.
21. Shafik A. Pudendal canal syndrome as a cause of vulvodynia and its treatment by pudendal nerve decompression. Eur J ObstetGynecolReprod Biol. 1998; 80(2):215–20.
22. Shafik A, El-Sherif M, Youssef A, Olfat ES. Surgical anatomy of the pudendal nerve and its clinical implications. Clin Anat. 1995; 8:110–5.
23. Erdogru T, Avci E, Akand M. Laparoscopic pudendal nerve decompression and transposition combined with omental flap protection of the nerve (Istanbul technique): technical description and feasibility analysis. SurgEndosc. 2014; 28(3):925–32.
24. E. de Bisschop, R. Nundlal. Surgical decompression of pudendal nerve by transperineal approach using a probe with a small balloon. Journal de Gyn ́ecologieObst ́etriqueetBiologie de la Reproduction; 2011: 40, 225—230.
25. Possover M. Laparoscopic management of endopelvic etiologies of pudendal pain in 134     consecutive patients. J Urol.2009 Apr; 181(4):1732-6.
26. Stanley J. Antolak. Pudendal nerve decompression surgery: Transgluteal technique. ICS Glasgow, Scotland August 2011.
27. Popeney C, Ansell V, Renney K. Pudendal entrapment as an etiology of chronic perineal pain: Diagnosis and treatment. NeurourolUrodyn.2007; 26(6):820-7.
28. Robert R, Labat JJ, Bensignor M, Glemain P, Deschamps C, Raoul S, et al. Decompression and transposition of the pudendal nerve in pudendal neuralgia: a randomized controlled trial and long-term evaluation. Eur Urol. 2005; 47(3):403–8.