Pudendal neuralgia (PN) is defined as the existence of pain in the distribution of the pudendal nerve. Pudendal neuropathy can occur in both genders. Entrapment of the pudendal nerve can give rise to perineal pain involving the penis, scrotum, labia, perineum, or anorectal region. Three sites of entrapment of the nerve have been described. These can occur along its path between the sacrotuberous and the sacrospinous ligaments (interligamentous plane), through Alcock canal, or as the nerve passes through a tight osteofibrotic canal at the entrance to the base of the penis.
Synonyms include pudendal nerve entrapment or the syndrome of the pudendal canal (Alcock canal). Clinicians rarely associate these symptoms with pudendal neuropathy. Conventional diagnoses include “prostatitis” or “prostadynia” in males or endometriosis or vulvodynia in females.
Pudendal neuralgia is a peripheral neuropathy of the pudendal nerve that occurs in one or both sides in both genders. Pudendal neuralgia is characterized by perineal (and other pelvic) pain that is aggravated by sitting, generally decreased by standing and recumbence and typically reduced or relieved by sitting on a toilet seat. Most cases of pudendal neuralgia can be by a combination of physical therapies and pain medications but in some cases injection treatment may help with diagnosis as well as pain relief. Pudendal nerve decompression should be consider in refractory cases.
As with any disorder of somatic sensation, pudendal neuralgia can arise from dysfunction of the central nervous system, the nerve trunk, or the “end-organ.” End-organ pathologies capable of producing symptoms of pudendal neuralgia include tumors, dermatological, gynecological, urological and proctological conditions.
The pudendal nerve is a mixed nerve containing somatic and autonomic afferent and efferent fibers. The nerve trunk develops from the sacral plexus anterior to the piriformis muscle. It is generally composed of fibers from anterior sacral rami S2, S3 and S4 although more complex segregation of sacral roots occurs. The nerve follows the posterior surface of the sacrospinous ligament, passes anterior to the sacrotuberous ligament, and enters the Alcock canal. Terminal branches are the dorsal nerve of the penis (clitoris), perineal nerve, and inferior anal nerve. Branches of the pudendal nerve may innervate the pubococcygeus muscle.
Pudendal neuropathy can be unilateral or bilateral. Causes include compression, stretch, direct trauma, and radiation. Pudendal neuralgia is a functional entrapment where pain occurs during a compression or stretch maneuver. The neuropathy worsens due to repetitive microtrauma resulting in persistent pain and dysfunctional complaints. The pudendal nerve is compressed during sitting and cycling and is especially damaged during motocross.
Stretch of the nerve by straining with constipation and childbirth can cause pudendal neuropathy. Fitness exercises, machines, weight lifting with squats, leg presses or karate with kick boxing and rollerblading are all etiologic factors. Youthful sports are a common denominator, possibly related to bony remodeling of the ischial spine. Driving over rough roads or farm fields causes vibration trauma. Falls onto the buttocks can cause pudendal neuralgia.
Iatrogenic neuropathy includes trauma during vaginal surgery and suture entrapment during colpopexy. Radiation neuropathy following treatment of carcinoma of the prostate may relate to vascular impairment, inflammation within the nerve, or perineural desmoplastic reaction. Central sensitization plays an important role in aggravation and maintenance of symptoms in many patients.
Pain aggravated by sitting, driving, exercise and reduced by recumbence or standing and relieved by sitting on a toilet, is pathognomonic. The quality of neuropathic pain varies and may be described as burning, stabbing, ache, or pressure. Pain may occur anywhere in the pudendal territory. Primarily this includes the perineum, scrotum (“testicles”), and penis/urethra but extends to suprapubic, inguinal, crural, anal, coccygeal regions, and the upper medial thighs. Scrotalgia and vulvodynia occur with pudendal neuropathy. Pain may be induced by voiding, defecating, ejaculation, vaginal penetration, orgasm, or simply with an urge to void or defecate. Stress and changes in the menstrual cycle aggravate pain. Foreign body sensation in the rectum, vagina, urethra, or perineum is frequent.
Physical examination focuses on a simple pudendal neurological evaluation. Pinprick sensation is tested at each branch bilaterally: dorsal nerve (clitoris and glans penis), perineal nerve (posterior labia and posterior scrotum), and inferior anal nerve (posterior perianal skin). Hyperalgesia is more common than hypoalgesia. Normal sensation to pinprick may occur even when quantitative sensory testing is abnormal. Pressure is placed on the nerve at the Alcock canal and medial to the ischial spine attempting to reproduce pain, bladder, or rectal symptoms—the Valleix phenomenon.
Several tests can measure pudendal neuropathy including sensory-evoked potentials, motor-evoked potentials, and motor latency tests. Electromyography of the external urethral and anal sphincters and the bulbocavernosus and ischiocavernosus muscles may show denervation and reinnervation.
MRI scan is the imaging of choice to rule out lumbar spine pathology and to look for specific pelvic pathology causing compression of the pudendal nerve. Visualization of pudundal nerve on MRI can be challenging, but with advances in MRI it may be possible to diagnose pudendal nerve entrapment.
Avoidance of injury and pain related to pudendal neuralgia is an important element of treatment. Patients who developed pain as a result of specific exercises such as cycling should avoid them if possible. Patients should use a cushion that supports the ischial tuberosities to elevate the pelvic floor off the seat. This support decreases the pressure applied to the pelvic floor muscles and pudendal nerve. Pain can cause spasm of the pelvic floor muscles and lead to increases in pressure on the nerve and a subsequent increase in pain levels. This vicious cycle is often very difficult to break and may lead to peripheral and central sensitization of pain. Some patients get better with lifestyle modifications alone.
In patients with muscle spasms, pelvic floor physical therapy is recommended to help relaxation of the pelvic floor muscles.
Medications can be used in patients who fail lifestyle modifications. Anti neuropathic drugs are the mainstay of management in pudendal neuralgia. These drugs include tricyclics, gabapentinoids and selective noradrenaline reuptake inhibitors (SNRIs).
Pudendal nerve blocks can be of diagnostic as well as therapeutic benefit. It involves injection of local anesthetic and steroid around the pudendal nerve, as it passes through the interligamentary space at ischial spine. A series of 3 injections is recommended at 4-weekly intervals. Injections should ideally be performed under fluoroscopy, CT or ultrasound guidance. Ultrasound has the advantage of showing the surrounding ligaments, muscles and blood vessels. Examination post-injection of six sites with pinprick detects analgesia or hypoalgesia (clitoris /glans, labia /posterior scrotum, and perianal area, bilaterally).
Botox injections into the pelvic floor muscles can relieve the spasm associated with these muscles. Patients with pelvic floor tension myalgia are likely to benefit from these injections.
Approximately one-third of patients with pudendal neuropathy will require surgical decompression. Transgluteal, perineal and transvaginal approaches have been described. Endoscopic and laparoscopic decompression have been used.