Condition deep dive
Pudendal nerve entrapment.
Entrapment is the mechanical, operable cause of pudendal neuralgia. Knowing which of the four anatomical sites is involved changes the diagnosis, the block strategy and the surgical approach.
The four entrapment sites
The pudendal nerve leaves the pelvis, hooks around the ischial spine and re-enters through the lesser sciatic foramen. It can be compressed anywhere along that path:
- Site I — between piriformis and coccygeus, before the sciatic notch
- Site II — the ligamentous clamp between the sacrospinous and sacrotuberous ligaments (most common)
- Site III — the Alcock canal, inside the obturator internus fascia
- Site IV — distal branches under the pubic arch (dorsal nerve of the penis/clitoris)
Symptoms by site
Proximal (site I–II) entrapment tends to produce the full territory: perineal, rectal and genital pain with sitting intolerance. Alcock canal entrapment (site III) often gives more urethral and anal-sphincter symptoms. Distal entrapment (site IV) can present as isolated glans or clitoral pain, sometimes only when cycling.
Mapping symptoms to a site is what makes an image-guided block diagnostic rather than a guess.
How entrapment is confirmed
There is no single test. Confirmation is a triangulation: Nantes clinical criteria, reproducible tenderness at the ischial spine on examination, MR neurography showing nerve swelling or asymmetry, and — critically — a positive response to an image-guided pudendal nerve block at the suspected site.
A negative MRI does not exclude entrapment. A positive block at the right site is a far stronger predictor of surgical benefit.
Decompression surgery
Transgluteal decompression divides the sacrospinous ligament, frees the nerve from the clamp, and opens the Alcock canal under direct vision. It is the only intervention that removes the mechanical cause rather than masking the pain.
Patient selection matters more than technique. Long duration of symptoms, widespread central sensitisation and unclear block response all reduce the expected benefit — and we say so before booking anyone for surgery.
Common questions
What is pudendal nerve entrapment?
Pudendal nerve entrapment is mechanical compression of the pudendal nerve along its course — most often between the sacrospinous and sacrotuberous ligaments at the ischial spine, or inside the Alcock (pudendal) canal. It is one specific cause of pudendal neuralgia, and the one that responds to surgical decompression.
How is entrapment different from pudendal neuralgia?
Pudendal neuralgia describes the pain syndrome. Entrapment describes a structural cause of it. Every entrapment produces neuralgia, but not every neuralgia is caused by entrapment — some cases follow viral injury, radiation, childbirth stretch injury or central sensitisation.
Where does the pudendal nerve get trapped?
The four classic sites are: (1) between the piriformis and coccygeus muscles, (2) in the clamp between the sacrospinous and sacrotuberous ligaments at the ischial spine — the most common, (3) within the Alcock canal in the obturator internus fascia, and (4) at the distal branches under the pubic arch.
What causes the nerve to become entrapped?
Long-distance cycling, prolonged sitting, childbirth, pelvic or spinal surgery, mesh procedures, falls onto the buttocks, and chronically tight pelvic floor muscles are the common triggers. In some patients, a congenitally narrow ligamentous clamp is enough on its own.
Can pudendal nerve entrapment be fixed?
Yes — transgluteal or transperineal pudendal nerve decompression releases the nerve from the ligaments and canal. Published series and our own outcomes show meaningful improvement in the majority of correctly selected patients, with the best results in those operated before pain becomes fully centralised.
Speak with a pudendal nerve specialist.
Dr Renaud Bollens leads a specialist practice dedicated to chronic pelvic pain, with centers in Dubai and Belgium.