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Pudenal Nerve Entrapment
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Pudendal nerve neuralgia from entrapment/compression is one of the major causes of chronic perineal pelvic pain. It is a condition similar to carpal tunnel syndrome where the nerve to the hand is compressed between the ligaments going to fingers causing numbness. Pudendal nerve entrapment was first recognised in 1987 as the Alcock's canal or cyclist's syndrome.
The pudendal nerve is one of the major nerves to the pelvis and external genitalia. The main symptoms of nerve entrapment are pain in one or more of the areas supplied by the pudendal nerve. In women this include the genital areas. In men the symptoms include the penis and scrotum which can also be confused with prostatitis; as a result many men are wrongly labelled to have chronic non-bacterial prostatitis.
Typically patients complains of pain in the perineum (area between rectum and vulva/scrotum), penis, scrotum in men and vulva, labia, vagina, clitoris in women. The pain is aggravated by sitting especially on a soft chair; relieved by standing, lying down or sitting on a toilet seat. The pain is described as a severe burning, tingling pain in the area supplied by the pudendal nerve or it can also be isolated in the rectum, vulva (scrotum) or clitoris (penile pain).
Patients with pudendal neuralgia may have symptoms other than pain. This includes pain with urination, urinary frequency, bowel movement, pain with intercourse or orgasm and sometimes persistent sexual arousal.
The symptoms of pudendal nerve neuralgia can mimic and therefore often misdiagnosed as prostatitis, cystitis, testicular pain, urinary hesitancy, endometriosis and proctalgia. As a result the average time to diagnosis of pudendal nerve entrapment is usually about 4 years.
Causes
The pudendal nerve can be compressed between the sacrotuberous and sacrospinous ligaments (clamp), the Alcocks canal or the falciform process of the sacrotuberous ligament. In approximately 70% of patients, pain is only on one side and in the remaining 30% the pain is on both sides of the body.
In many patients, the reason for the injury of the pudendal nerve is not known. Some of the known causes of pudendal nerve injury are trauma to the pelvic area, gynaecologic surgery (hysterectomy, repair of bladder prolapse, surgery for incontinence), stretching of the pudendal nerve from chronic constipation, normal vaginal delivery and prolonged sitting.
In cases of surgical injury, onset of pain is usually sudden but in most cases the onset of pain is slow and progresses over many months or years.
Diagnosis of pudendal neuralgia is mainly a clinical diagnosis. There are no exclusive tests for pudendal nerve entrapment.
The criteria (Nantes criteria) used for diagnosis are:
1.Pain in the area of the pudendal nerve.
2.Worsened by sitting & relieved by sitting on toilet or standing.
3.The patient is not woken at night by the pain.
4.No objective sensory loss on clinical examination.
5.Positive anaesthetic pudendal nerve block.
Some groups use electromyography to test the nerve function but this can be confusing and unreliable. Professor Roberts group in Nantes have stopped using this test for this reason.
Treatment of pudendal neuralgia consists of conservative and surgical treatments.
Conservative treatments include avoiding activities that caused or aggravate the injury (eg. cycling), analgesic/anti-inflammatory medications and physiotherapy/chiropractic manipulations.
If there is no improvement then steroid and local anaesthetic nerve blocks may be offered. This will reduce the pain as well as swelling and inflammation around the nerve.
Surgery is offered if there is no long-term relief of pain.
The aim of surgery is to free the pudendal nerve from any compression. The surgical approaches to pudendal nerve decompression include trans-gluteal, trans-ischiorectal and trans-perineal approaches. Recently a laparoscopic approach has been described but there is no published result of its efficacy.
The trans-gluteal approach, originally described by Professor Roger Robert in Nantes, France gives the best visualization of the nerve from the clamp (sacrotuberous and sacrospinous ligaments) to the falciform process and Alcock's canal. A 5cm incision is made in the buttock and the ligaments and falciform process are divided. The Alcock's canal is also dilated. The nerve is then transposed into the pelvis travelling in a shorter route.
Outcome
Outcomes from pudendal nerve decompression surgery depend on many factors such as duration of pain, degree and cause of nerve injury. Approximately 40% of patients who undergo trans-gluteal pudendal decompression have significant improvement in pain, 30% of patients have some improvement in pain (overall 70% improvement), 30 % have no change in pain and 1% may get worse.
Unlike nerve blocks improvement after surgery is usually not felt until 4-6 months from surgery and takes up to 12-18 months for complete recovery.
