European European Urology 47 (2005) 403–408

Urology

Decompression and Transposition of the Pudendal Nerve

in Pudendal Neuralgia: A Randomized Controlled Trial
and Long-Term Evaluation
Roger Roberta, Jean-Jacques Labatb,*, Maurice Bensignorc, Pascal Glemainb,
Cédric Deschampsc, Sylvie Raoulc, Olivier Hamelc
a
Neurotraumatologie, Hotel Dieu Chu Nantes, 44093 Nantes Cedex 1, France
b
Clinique Urologique, Hôtel Dieu Chu Nantes, 44093 Nantes Cedex 1, France
c
Unité d’évaluation et de traitement de la douleur, Centre Catherine de Sienne, 2 rue Eric Tabarly, 44200 Nantes, France
Accepted 13 September 2004
Available online 30 September 2004

Abstract
Background: We assess that pudendal neuralgia is a tunnel syndrome due to a ligamentous entrapment of the
pudendal nerve and have treated 400 patients surgically since 1987. We have had no major complication. We
conducted a randomized controlled trial to evaluate our procedure.
Methods: A sequential, randomized controlled trial to compare decompression of the pudendal nerve with non-
surgical treatment. Patients aged 18–70, had chronic, uni/bilateral perineal pain, positive temporary response to
blocks at the ischial spine and in Alcock’s canal. They were randomly assigned to surgery (n = 16) and control
(n = 16) groups. Primary end point was improvement at 3 months following surgery or assignment to the non-
surgery group. Secondary end points were improvement at 12 months and at 4 years following surgical intervention.
Results: A significantly higher proportion of the surgery group was improved at 3 months. On intention-to-treat
analysis 50% of the surgery group reported improvement in pain at 3 months versus 6.2% of the non-surgery group
(p = .0155); in the analysis by treatment protocol the figures were 57.1% versus 6.7% (p = .0052). At 12 months,
71.4% of the surgery group compared with 13.3% of the non-surgery group were improved, analyzing by treatment
protocol (p = .0025). Only those randomized to surgery were evaluated at 4 years: 8 remained improved at 4 years.
No complications were encountered.
Conclusions: In this study we demonstrate that decompression of the pudendal nerve is an effective and safe
treatment for cases of chronic pudendal neuralgia that have been unresponsive to analgesia and nerve blocks.
Following surgery, other medical interventions may be necessary.
# 2004 Elsevier B.V. All rights reserved.

Keywords: Neuralgia; Pelvic pain; Perineum; Sacral plexus; Neurosurgical procedure; Nerve compression
syndromes; Prostatitis

1. Introduction drome, and levator ani syndrome. The diagnosis of

pudendal neuralgia [2,3] is based on clinical symp-
Patients suffering from chronic perineal pain may be toms: chronic debilitating perineal pain that is usually
assigned several diagnoses including prostatodynia, exacerbated in the seated position and relieved by
prostatitis, vulvodynia, chronic pelvic pain [1] syn- standing, there is no nocturnal pain, normal imaging
and the pain is unresponsive to usual analgesics. To our
* Corresponding author. Tel. +33 240083910; Fax: +33 240032683. knowledge, there is no statistical study about the
E-mail address: jjlabat@club-internet.fr (J.-J. Labat). frequency of pudendal neuralgia in the literature.
0302-2838/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.eururo.2004.09.003
404 R. Robert et al. / European Urology 47 (2005) 403–408

Our team treats 700 patients a year for perineal pain

without any urologic, gynecologic and proctologic
explanation. Among them, 200 have the diagnostic
criterias of pudendal neuralgias as described above.
70 of them have no benefit with traditional antalgic
treatment including the specific blocks. Finally, 40
patients out of 700 will be operated.
We have previously shown that the pudendal nerve
can be subject to a ligamentous entrapment and that
decompression and transposing the pudendal nerve
may benefit patients with chronic pain [4]. We have
operated on 400 patients since 1987 [5] and our
surgical findings reinforce our view that a broad sur-
gical release is necessary contrary to what has been
proposed by others (and not evaluated) [6]. We wished
to confirm objectively whether our clinical experience
was valid. We therefore conducted a prospective ran-
domized controlled trial to assess our procedure.
Fig. 1. Ischial spine block (fluoroscopy): Following antiseptic preparation
of the skin, a 22G-90 mm spinal needle is inserted vertically just medially to
the ischial spine. An injection is made with 4 ml of 1% lidocaine and 40 mg
2. Methods methylprednisolone acetate.

2.1. Study inclusion criteria tion of the pudendal nerve. Medical treatment of the pain was
Patients eligible for inclusion in the study had chronic perineal identical in the two groups during follow up. It included anti-
pain of at least one year’s duration in the area served by the convulsant and antidepressant medications for neuropathic pain,
pudendal nerve. Pain could be unilateral or bilateral, was exacer- relaxation and behavioral therapy. Steroid pudendal nerve blocks,
bated in the seated position, and was not marked at night. Patients were administered when the pain was unresponsive to analgesics.
had to be between the ages of 18–70, in good general health, have a Several techniques have been described for carrying out pudendal
pain intensity of at least 70 mm on a 100 mm visual analogue scale nerve blocks. We used two principal transgluteal approaches: at the
(VAS) [7] a minimum score of 3 on the behavior scale (Table 1), a ischial spine (IS) (Fig. 1) and in Alcock’s canal (Fig. 2). The
positive diagnostic response to an anesthetic block of the pudendal diagnostic test is the temporary relief of the pain as a result of the
nerve defined as numbness in the usually painful area after nerve local anaesthetic. A secondary therapeutic effect resulting from the
block with a temporary reduction in pain while seated, persistence steroid can be expected. In our previous experience, there is a
of perineal pain in spite of at least two steroid blocks of the reduction in pain in two thirds of patients with 2–3 blocks each,
pudendal nerve at the ischial spine and in Alcock’s canal [8] no over a period of 6 months. We find it appropriate to perform the
evidence from pelvic CT scans of pelvic or perineal pathology, and blocks at minimum intervals of 6–8 weeks and to limit the number
a depression score of 9 or below on the sub-scale of 6 items of the of blocks to 2–4.
‘‘depressive score’’ on the Hamilton depression rating scale [9,10] Physiotherapy was offered especially when a myofascial com-
ponent was identified (triggers points localized in piriformis,
2.2. Study design obturator internis or levator ani muscles) and consisted of muscle
The study was a sequential, randomized controlled trial, without stretches and relaxation [11].
blinding. Eligible patients gave informed consent after reading The only difference, in the treatment, between the two groups is
written information on the study. The ethics committee of the related to the fact that only the patients in the first group were
Nantes Centre Hospitalier et Universitaire (Comité Consultatif operated on.
pour la Protection des Personnes en Recherche Biologique)
approved the protocol. The source of funding was the CHU of 2.3. Surgical procedure
Nantes. Patients who agreed to participate were assigned randomly The transgluteal approach that we have described in 1989 [5]
to one of two treatment groups: surgery or control. Those in the following Amarenco’s hypothesis [12], allows all possible entrap-
surgery group were offered surgical decompression and transposi- ments that we have detailed to be corrected in a single incision.

Table 1
Six-point behavior scale

(0) No pain
(1) Pain present but can easily be ignored
(2) Pain present, cannot be ignored but does not interfere with daily activities
(3) Pain present, cannot be ignored, interferes with concentration
(4) Pain present, cannot be ignored, restricting all activities except basic needs such as washing and feeding
(5) Pain present, cannot be ignored. Bed rest necessary.
 R. Robert et al. / European Urology 47 (2005) 403–408 405

dilatations. The closure is effected in three planes. The sacrifice of

the two ligaments has no morbid consequences for the sacro-iliac
joint. The duration of surgery for one nerve is about 30 minutes. A
3–5 days hospital stay is required.

2.4. Outcome measures

The primary endpoint of the study was the proportion of patients
judged to have improved at three months following surgery or after
3 months of medical treatments. Two principal outcome criteria
were used: pain evaluated on a VAS, and quality of life, evaluated
on a 6-point self-rated behavioral scale (Table 1). Treatment was
considered effective if the pain score had decreased by at least
30 mm on the VAS and if the effect on quality of life rated less than
3 on the behavior scale. We followed up both groups at 1 year and
Fig. 2. Alcock’s canal block (CT scan): The patient is installed in prone the surgical group was assessed again at 4 years to find out whether
position. The ideal course of the needle is simulated on the screen by joining improvement was maintained.
the posterior edge of the symphysis pubis to the internal edge of the ischium,
passing between the obturator internus and its aponeurosis, and in extending 2.5. Statistical methods
this line back to the skin. The needle is inserted obliquely remaining in the Due to the difficulty in blinding surgical techniques, the study
vertical plane defining the section, parallel to the fascia of the obturator was not blinded. The Medical Computing and Statistics Unit
internus. carried out the randomization, balanced with unequal block sizes,
independently of the investigators [13]. Efficacy in 60% of patients
at 3 months was assumed in the surgical group and in 30% of
There are two main entrapment locations, eventually associated: in patients in the non-surgery group. To establish a statistically
the claw between the sacrospinous and sacrotuberous ligaments significant difference of this size, with a p value of 5% in a
near the ischial spine, in the Alcock’s canal due to the falciform one-tailed test and 90% power, using a sequential design, with
process of the sacrotuberous ligament and/or fascia of the obturator analysis of efficacy every 8 cases and the triangular test, a max-
internus muscle. imum of 48 study participants was estimated.
Under general anesthesia, a gluteal incision of about 7 cm in
length is made on both sides of a transversal line from the top of the
coccyx, oriented obliquely according to the direction of the gluteus
maximus muscle fibres, which are dissected and disinserted from 3. Results
the sacrotuberous ligament. The narrow section of the sacrotuber-
ous ligament, located at the level of the ischial spine, is then Between June 1994 and July 1996, 181 patients were
resected transversally. The pudendal neurovascular bundle is then
seen in a multidisciplinary clinic for perineal pain and
visible and released from the dorsal surface of the sacrospinous
ligament. A simple retractor holding medially the ischio-rectal fat of these, 35 were eligible for the study (patients pre-
is sufficient to open the pudendal canal. It is then possible to senting with resistant pudendal neuralgia and potential
perform a digitoclasic release of the nerve. If the fascia of the candidates for surgical decompression). Three patients
obturator is thickened or the falciform process is threatening, these refused to participate. The other 32 (23 women and 9
can be incised. The sacrospinous ligament is cut and the nerve can
men) were recruited in sequence and randomized, 16 to
then be transposed frontally to the ischial spine. One may then
assess the diameter of the nerve, its shape (flattened or not), its each of the study groups. The analysis of these 32
inflammatory appearance, peritroncular fibrosis and satellite veins patients reached statistical significance and we there-

Table 2
Baseline characteristics of the two groups

Surgery (n = 16) (mean  S.D. (range)) Control (n = 16) (mean  S.D. (range)) p value*

Gender Female: 12 Female: 11

Male: 4 Male: 5
Age 51.8  11.8 (24–70) 56.4  8.4 (40–67) 0.23
Duration of symptoms (years) 6.2  4.8 (1–16) 3.4  2.8 (1–30) 0.12
Mean pain score (VAS) 82.9  8.7 (72–100) 85.2  9.2 (72–100) 0.48
Mean behavior score 3.9  0.7 (3–5) 4.1  07 (3–5) 0.36
Hamilton score total 8.1  4.6 (2–18) 11.2  5.3 (5–22) 0.10
Hamilton score depression 3.6  1.9 (0–8) 4.2  2.4 (0–8) 0.50
Latency of bulbo-cavernous reflex right (ms) 51.0  21.0 (30–86) 39.3  5.0 (38–43) 0.71
Latency of bulbo-cavernous reflex left (ms) 43.1  12.0 (32–65) 43.3  7.4 (33–60) 0.17
Pudendal nerve latency right (ms) 4.2  2.4 (1.7–7.8) 5.3  0.6 (4.6–5.6) 0.29
Pudendal nerve latency right (ms) 4.6  1.9 (0.6–7.7) 6.0  2.6 (2.4–10) 0.16
*
Non-parametric Mann–Whitney U test.
406 R. Robert et al. / European Urology 47 (2005) 403–408

Table 3 success had VAS scores under 40 at 12 months. The 4

Results at three months (primary end point)
patients who had surgery and were classified as failures
Intent to treat, Per protocol, at 12 months remained failures at 4 years. The 2 cases
n (%) (n = 32) n (%) (n = 29) classified as a success at 12 months, but as failures at 4
Success Failure Success Failure years, had pain ratings of over 40 mm at the 12-month
Surgery 8 (50.0) 8 (50.0) 8 (57.1) 6 (42.9)
follow-up. It therefore appears that pain intensity at 1
Control 1 (6.2) 15 (93.8) 1 (6.7) 14 (93.3) year indicates long-term results whatever the initial
Fisher exact test 0.0155 0.0052 score was.
In this study, we had no complication (infection,
hematoma, neurological impairment, increasing of
fore discontinued the study at this point, according to pain).
the sequential procedure decided, at its start. Table 2
shows that there were no significant differences
between the groups with respect to baseline character- 4. Discussion
istics. Following allocation, 2 patients in the surgery
group withdrew from the study before surgery, and one 4.1. Overall results
patient in the control group withdrew before the 3- This study demonstrates that surgical decompres-
month endpoint. These three cases are classed as fail- sion of the pudendal nerve in intractable pudendal
ures in the intention-to-treat analysis at 3 months. neuralgia is effective for patients in whom medical
Table 3 shows that at 3 months, pain was alleviated treatment, physical therapy and nerve blocks have
significantly more often in the surgery than in the failed. Although a success rate of 10 out of 14 at
control group (intention-to-treat analysis): eight one year may not seem high, it is a good outcome
patients (50%) of the surgery group were improved for a chronic pain syndrome where more conservative
versus 1 patient (6.2%) of the control group treatments have failed. Patients included in this
(p = 0.0155). In the analysis by treatment protocol protocol had high VAS scores (7/10); 10 out of 14
the figures are 8 improved patients (57.1%) versus 1 clearly improved 3 points on the VAS by surgical
patient (6.7%) (p = 0.0052). Among 15 patients of the treatment. Four of them are painless (VAS = 0). These
control group, 6 had blocks during this period versus 4 results are quite different comparatively to the control
out of 14 in the surgical group. At 3 months, 9 of the 16 group.
patients in the control group wished to transfer to The surgical procedure is therefore validated and
surgical treatment. They were not included in the can reasonably be proposed for such patients. The
surgical protocol and were all considered as failures efficacy of the surgery confirms the etiology of these
of the non-surgical treatment at 12 months. Six others postural perineal pain syndromes, previously consid-
elected to continue with medical treatment. ered as organs pathology (i.e., prostatodynias, vulvo-
At 12 months in the analysis by treatment protocol dynias, levator ani syndrom, . . .).
(Table 4) 10 patients in the surgery group (71.4%) and Like in very common entrapment syndromes, no
2 controls (13.3%) had a successful outcome as defined risk factors can be defined. Prevalence of women
for the study (p = 0.0025). Four of them are painless (60%) may be explain by parturition; sport as bike
(VAS = 0). The surgery group was assessed again at 4 clearly exposes to this pathology [12].
years. Eight of the 10 patients classified as successes at
one year, remained so at 4 years. Seven of them had 4.2. Time-interval to evaluation
VAS pain scores of less than 15 mm and were con- Assessment at 3 months was chosen for the primary
sidered completely cured. The eighth patient had a end point and at 12 months for the secondary end point.
score of 38. Thus all patients considered as long lasting This choice may seem inappropriate in the evaluation
of chronic pain, but has been shown here to be relevant
Table 4
because although it does not necessarily give the
Results at 12 months (secondary end point): analysis by treatment protocol definitive result, it nevertheless reveals the efficacy
(n = 29) of the surgery compared with no surgical intervention.
Success, n (%) Failure, n (%) For ethical reasons, it seemed difficult to do the initial
evaluation after more than 3 months. In fact, several
Success 10 (71,4%) 4 (28,6%)
Failure 2 (13.3%) 13 (86.7%)
patients of the control group decided to go out of the
protocol in order to be operated. So, they have not been
Fisher exact test 0.0025
evaluated at 12 months. However we also followed up
 R. Robert et al. / European Urology 47 (2005) 403–408 407

all patients at 12 months. It is interesting to note that eral. However it is likely that patients with such fibrosis
two additional patients were improved at 12 months would experience a temporary improvement with sec-
compared with the 8 noted at 3 months. The interval of ondary relapse rather than primary failure. Fibrosis
12 months appears a suitable indicator of lasting may nevertheless explain the two cases in our series
success as patients having had a good result at 12 that had improved at 12 months but had relapsed at 4
months retain this at 4 years if their pain score was years.
below 40 mm at 12 months. We could also have missed a contralateral entrap-
ment in unilateral cases despite careful assessment.
4.3. Design But, if so, we would expect the patient to experience
The study was randomized but not blinded, as we postoperative pain mainly on the non-operated side.
believed blinding would not be ethically acceptable. Intractable chronic pain has significant emotional
We would have had to inflict a buttock incision as sham consequences and a psychological component is an
surgery for the control group. In any case, the surgical integral part of the pain process. Although we tried to
results far exceed what would be expected from any exclude patients with severe depression using a depres-
placebo effect. Placebo effects may be substantial sion scale, the emotional, psychological and social
when managing acute pain but have been shown to distress may be important factors of resistance to
be much less so in chronic pain [14,15]. treatment in all chronic pain syndromes.

4.4. Safety and feasibility

No complications occurred during this series, con- 5. Conclusions
firming our previous experience of 400 patients that
this procedure is safe and the operative risk is negli- This prospective, randomized study demonstrates
gible. that decompression and transposition of the pudendal
Surgery never damages the nerve. As in classical nerve is a safe and effective treatment for patients with
surgery for entrapment syndroms, the goal is to release intractable pudendal neuralgia refractory to other treat-
any source of entrapment, we never found any ments. This diagnosis must be clearly defined by
hypoesthesia nor motor complication after surgery. clinical (chronic debilitating perineal pain, exacerbated
in the seated position and relieved by standing, no
4.5. Failure analysis nocturnal pain, normal imaging), neurophysiological,
Several reasons can be suggested for surgical fail- and diagnostic blocks tests. The success of a surgical
ures: approach also lends credence to our hypothesis that this
Diagnostic error is always possible although we type of pain is due to a tunnel syndrome and may offer
offer surgery only to patients with a convincing clinical a new approach to patients with chronic perineal,
picture and we found entrapped nerves in all. urogenital or anorectal pain previously misdiagnosed
Long lasting or tight compression preoperatively or abusively qualified as ‘‘idiopathic’’ or ‘‘psycho-
could account for irreversible nerve fibers damage genic’’.
initiating chronic neuropathic pain. Relieving the
entrapment might not be sufficient to initiate complete
nerve recovery. Acknowledgements
Incomplete release of the pudendal nerve could be
responsible, particularly if the entrapment was at the We appreciate the help rendered by: CHU de
distal part of the Alcock’s canal and could not be Nantes, promotor of the study; Dr. Jean-Paul N’Guyen
reached through our surgical approach. for statistical methods; Mr. Dominique Le Forestier for
Postoperative fibrosis is also a recognized source of the photographs and Laboratory of Anatomy – Faculty
persistent pain following nerve decompression in gen- of Medicine of Nantes (Pr Joël Le Borgne).

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