Pudendal nerve entrapment (PNE), also known as Alcock canal
syndrome, is an uncommon source of chronic pain, in
which the pudendal nerve (located in the pelvis) is entrapped or
compressed. Pain is positional and is worsened by sitting. Other
symptoms include genital numbness, fecal incontinence and urinary
The term pudendal neuralgia (PN) is used interchangeably with
"pudendal nerve entrapment", but a 2009 review study found both that
"prevalence of PN is unknown and it seems to be a rare event" and that
"there is no evidence to support equating the presence of this
syndrome with a diagnosis of pudendal nerve entrapment," meaning that
it is possible to have all the symptoms of pudendal nerve entrapment
(otherwise known as pudendal neuralgia) based on the criteria
specified at Nantes in 2006, without having an entrapped pudendal
A 2015 study of 13 normal female cadavers found that the pudendal
nerve was attached or fixed to the sacrospinous ligament in all
cadavers studied, suggesting that the diagnosis of pudendal nerve
entrapment may be overestimated.
2 Tests and Imaging
4.1 Physical therapy
4.4 Pulsed radiofrequency
6 External links
There are no specific clinical signs or complementary test results for
this condition. The typical symptoms of PNE or PN are seen, for
example, in male competitive cyclists (it is often called "cyclist
syndrome"), who can rarely develop recurrent numbness of the penis
and scrotum after prolonged cycling, or an altered sensation of
ejaculation, with disturbance of micturition (urination) and reduced
awareness of defecation. Nerve entrapment syndromes,
presenting as genitalia numbness, are amongst the most common
bicycling associated urogenital problems.
The pain is typically caused by sitting, relieved by standing, and is
absent when recumbent (lying down) or sitting on a toilet seat. If
the perineal pain is positional (changes with the patient's position,
for example sitting or standing), this suggests a tunnel syndrome.
Anesthesiologist John S. McDonald of
UCLA reports that sitting pain
relieved by standing or sitting on a toilet seat is the most reliable
Other than positional pain and numbness, the main symptoms are fecal
incontinence and urinary incontinence.
Differential diagnosis should consider the far commoner conditions
chronic prostatitis/chronic pelvic pain syndrome and interstitial
Tests and Imaging
Similar to a tinel sign digital palpitation of the ischial spine may
produce pain. In contrast, patients may report temporary relief with a
diagnostic pudendal nerve block (see Injections), typically
infiltrated near the ischial spine.
Electromyography can be used to measure motor latency along the
pudendal nerve. A greater than normal conduction delay can indicate
entrapment of the nerve.
Imaging studies using MR neurography may be useful. In patients with
unilateral pudendal entrapment in the Alcock's canal, it is typical to
see asymmetric swelling and hyperintensity affecting the pudendal
PNE can be caused by pregnancy, scarring due to surgery, accidents and
surgical mishaps. Anatomic abnormalities can result in PNE due to
the pudendal nerve being fused to different parts of the anatomy, or
trapped between the sacrotuberous and sacrospinalis ligaments. Heavy
and prolonged bicycling, especially if an inappropriately shaped or
incorrectly positioned bicycle seat is used, may eventually thicken
the sacrotuberous and/or sacrospinous ligaments and trap the nerve
between them, resulting in PNE.
Optional treatments include behavioral modifications, physical
therapy, analgesics and other medications, pudendal nerve block, and
surgical nerve decompression. A newer form of treatment is pulsed
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There are stretches and exercises which have provided reduced levels
of pain for some people. There are different sources of pain for
people since there are so many ligament, muscles and nerves in the
area. Sometimes women do pelvic floor exercises for compression after
childbirth. However, there have been cases where the wrong stretches
make the constant pain worse. Some people need to strengthen the
muscles, others should stretch, while for some people it is purely
neurological. There have been cases where doing stretches have helped
Acupuncture has helped decrease pain levels for some
people, but is generally ineffective. Chiropractic
adjustments to the lower back have also helped some patients with
pudendal nerve issues.
There are numerous pharmaceutical treatments for neuropathic pain
associated with pudendal neuralgia. Drugs used include anti-epileptics
(like gabapentin), antidepressants (like amitriptyline), and
Alcock canal infiltration with corticosteroids is a minimally invasive
technique which allows for pain relief and could be tried when
physical therapy has failed and before surgery. A long-acting local
anesthetic (bupivacaine hydrochloride) and a corticosteroid (e.g.
methylprednisolone) are injected to provide immediate pudendal
anesthesia. The injections may also bring a long-term response
because the anti-inflammatory effects of the steroid and
steroid-induced fat necrosis can reduce inflammation in the region
around the nerve and decrease pressure on the nerve itself. This
treatment may be effective in 65–73% of patients.
Pulsed radiofrequency has been successful in treating a refractory
case of PNE.
Various ergonomic devices can be used to allow an individual to sit
while helping to take pressure off of the nerve. With bicycles the
seat height and tilt can be adjusted to help alleviate compression.
There are also bicycle seats designed to prevent pudendal nerve
compression, these seats usually have a narrow channel in the middle
of them. For sitting on hard surfaces, a cushion or coccyx cushion can
be used to take pressure off the nerves.
Decompression surgery is a "last resort", according to surgeons who
perform the operation. The surgery is performed by a small number
of surgeons in a limited number of countries. The validity of
decompression surgery as a treatment and the existence of entrapment
as a cause of pelvic pain are highly controversial. While a
few doctors will prescribe decompression surgery, most will not.
Notably, in February 2003 the
European Association of Urology in its
Guidelines on Pelvic Pain said that expert centers in Europe have
found no cases of PNE and that surgical success is rare:
Pudendal nerve neuropathy is likely to be a probable diagnosis if the
pain is unilateral, has a burning quality and is exacerbated by
unilateral rectal palpation of the ischial spine, with delayed
pudendal motor latency on that side only. However, such cases account
for only a small proportion of all those presenting with perineal
pain. Proof of diagnosis rests on pain relief following decompression
of the nerve in Alcock’s canal and is rarely achieved. The value of
the clinical neurophysiological investigations is debatable; some
centres in Europe claim that the investigations have great
sensitivity, while other centres, which also have a specialized
interest in pelvic floor neurophysiology, have not identified any
— European Association of Urology, Guidelines on Chronic Pelvic
Three types of surgery have been done to decompress the pudendal
nerve: transperineal, transgluteal, and transichiorectal. A follow-up
of patients of this surgery after 4 years found that 50% felt their
pain had improved to various extents, although control patients were
not followed up for comparison. If surgery does bring relief of
symptoms, patients will mostly experience it within 4 weeks of
However, the studies and surgical methods cited above generally
focused on the Alcock’s canal and the area between the sacrotuberous
and sacrospinous ligaments as likely sites for entrapment. More recent
studies have identified possible entrapment sites anterior to
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Pudendal nerve decompression in perineology : a case series
Nervous system pathology, PNS, somatic (G50–G64, 350–357)
Nerve, nerve root, plexus
V Trigeminal neuralgia
Facial nerve paralysis
Accessory nerve disorder
Brachial plexus lesion
Thoracic outlet syndrome
Carpal tunnel syndrome
Ape hand deformity
Ulnar nerve entrapment
Guyon's canal syndrome
long thoracic nerve:
lateral cutaneous nerve of thigh:
Tarsal tunnel syndrome
superior gluteal nerve:
Nerve compression syndrome
Hereditary spastic paraplegia
Hereditary neuropathy with liability to pressure palsy
Familial amyloid neuropathy
Chronic inflammatory demyelinating polyneuropathy