Pudendal Nerve Entrapment
 
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 nerve.

 

Pathology:

Difficult childbirth or bicycling can compress or stretch the pudendal nerve, causing temporary loss of function, but permanent injury is rare. 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 (Figure-1). 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. Entrapment of the nerve due to pelvic tumor is very rare but can happen. A pelvic tumor (most notably a large sacrococcygeal teratoma), or pelvic surgery to remove the tumor, can damage this nerve permanently. A pudendal nerve block is a common obstetric procedure to anesthetize the perineum during labor.
 
 
Figure-1: PNE between sacrospinous and sacrotuberous ligaments
Pudendal Nerve Entrapment

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 as it leaves or enters the pelvis in various tunnels created by adjacent muscles, tendons or bony and ligamentous tissues.

In this condition the nerve is most commonly compressed at:

  • The space between sacrotuberous and sacrospinous ligaments (~70% cases)
  • Within the pudendal canal of Alcock (~20% cases) - While straddling of the falciform process of the sacro-tuberal ligament by the pudendal nerve and its branches
  • Anywhere along the course of the pudendal nerve or its branches It is thought that changes in the shape and position of the ischial spine occur in young cyclists. This predisposes them to pudendal nerve entrapment in later years especially if they continue to cycle for prolonged periods. The most common causes for pudendal nerve entrapment syndrome include:
  • Repeated mechanical injury (e.g. sitting on bicycle seats for prolonged periods over many years or months)
  • Trauma to the pelvic area
  • Damage to the nerve during surgical procedures in the pelvic or perineal regions
  • Compression from lesions or tumours arising in the pelvis
  • Any cause for the development of peripheral neuropathy (e.g. diabetes or vasculitis).

    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 nerve.

    Differential diagnosis should consider the far commoner conditions: chronic prostatitis/chronic pelvic pain syndrome in male and interstitial cystitis in female. The symptoms of pudendal nerve entrapment overlap considerably with those ascribed to chronic nonbacterial prostatitis, which is the most common symptomatic type of prostatitis, or chronic pain syndrome. In the United States, chronic prostatitis is the reason for an estimated 7.8 million physician visits per year; approximately 95% of men with chronic prostatitis do not have an infection.

    The cause of chronic nonbacterial prostatitis-chronic pelvic pain syndrome remains unclear, but the syndrome has never been scientifically shown to be primarily a disease of the prostate or the result of an inflammatory process. Chronic nonbacterial prostatitis causes substantial morbidity and affects the health of a patient to the same degree as do conditions such as acute myocardial infarction, unstable angina, and acute ulcerative colitis. Proper diagnosis and treatment of pudendal nerve entrapment with CT-guided pudendal nerve perineural injection offer some patients with chronic nonbacterial prostatitis-chronic pelvic pain syndrome a chance of long-term pain relief.