Pubic neuralgia is a chronic severe pain in the vaginal, vulvar, anal canal and perineal areas without organic pathology and difficult to diagnose and treat definitively. The incidence of pubic neuralgia is unclear, and it is a rare condition that involves both men and women. It usually develops between the ages of 40 and 70.
Typical female patients present with pain in the labia, perineal area or anorectal area, while men present with pain in the penis, scrotum and perineal area. The pain is worse in sitting position, relieved in standing position, and disappears when lying or sitting on the toilet. Perineal neuralgia is often delayed or misdiagnosed, leading to unnecessary surgical procedures. Many gynecological conditions are also incorrectly diagnosed as pubic neuralgia because the etiology of the pain is not clear. Pain can also be caused when the pubic nerve is damaged after a pelvic fracture or surgical procedure.
1. Anatomy
The pubic nerve originates from the anterior horn neurons of the sacral segment of the spinal cord (S2-4), then travels medially and caudally to the sciatic nerve, and enters the gluteal region through the foramen magnum of the sciatic foramen via the inferior foramen of the pyriform muscle. The pubic artery accompanies it, and the veins surround it in a plexus pattern. The pubic nerve trunk crosses the sacrospinous ligament close to the sciatic spine, and at this level, the pubic nerve lies between the ventral sacrospinous ligament and the dorsal sacral tubercle ligament; in rare cases, the pubic nerve travels in the sacral tubercle ligament cleft. The nerve trunk then enters the perineal area ventrally, medially, and caudally via the sciatic foramen, and enters the foraminal fascia overlap at the inferior level of the anal levator muscle to form the pubic canal (Alcock’s canal).
In most cases, three neurovascular bundles originate from the canal: the anal nerve, the perineal nerve, and the dorsal clitoral nerve. The anal nerve innervates the perineal area and communicates with the perineal branch of the posterior femoral cutaneous nerve, the terminal branch of which is the labia majora nerve. It can sometimes originate directly from the sacral plexus or before the pubic nerve enters the pubic canal. The perineal nerve has a motor branch and two superficial sensory branches (the medial and lateral branches of the posterior labial nerve), which innervate the perineal area and ipsilateral posterior labia majora sensation, as well as the deep and superficial transverse perineal muscles, the bulbocavernosus muscle, the urethral bulbocavernosus muscle, the urethral sphincter and the anal levator muscle. This branch originates from the posterior part of the pubic canal.
The dorsal penile (clitoral) nerve is the terminal branch of the pubic nerve at the level of the pubic symphysis, which is the afferent nerve for clitoral sensation. Although the anatomy of the branches of the pubic nerve is well dissected, there are many variations within the sciatic rectal fossa and within the pubic canal. Since its branches mostly travel on the surface of the pelvis, they are vulnerable to injury.
2.Symptoms
Neuralgia in the pubic area is often manifested as pain in the vagina, labia, mons pubis and clitoris area in women. The pain and sensory abnormalities can spread to the groin area, inner thighs, buttocks and abdomen, and can involve one, several or all of these areas. It usually starts in one area and worsens progressively with unilateral attacks. It can also be bilateral, and one side may be distinctly different from the other. The pain is severe, sharp, sometimes burning, and often not relieved by analgesics. Pain has been reported to be significantly worse in the sitting position, and many patients have pain in the lying position and have difficulty sleeping. Patients may be awakened by concomitant symptoms (e.g., urgency to urinate) and are rarely awakened by pain.
Pain can be relieved to varying degrees by sitting on an empty lap pillow or on the toilet, which relieves pressure on the nerves. Sensory sensitization of the skin in the area may occur. The clinical presentation of pubic neuralgia can reflect the type of nerve damaged (motor, sensory, autonomic). The patient’s history often progresses from an automatic recovery process to a chronic, progressive exacerbation process that affects the patient’s daily life. Accompanying symptoms may include constipation, painful defecation, delayed urination, urinary frequency, urinary urgency and sexual dysfunction.
3.Pathophysiology
The pathogenesis is unclear, but the basic etiological hypothesis is that the injury is caused by stretching or compression of the pubic nerve. It is usually unilateral and rarely bilateral. Causes of nerve injury include: sciatic spine fractures due to tumors, compression of the falciform portion of the sacrocolic ligament, compression during transcatheter Alcock’s canal, bicycling, herpes simplex infection, compression by tumors or endometriosis, chemotherapy for rectal cancer, constipation, and stretching of the vaginal prolapse. Medically induced injuries include nerve blocks in the pubic area, effects on nerves and blood flow during surgical exploration of the pelvic cavity, and injury to nerves from muscle strains during lower extremity surgery. Since the pubic nerve travels lateral to the sacrospinous ligament, knots tied laterally to the ligament during sacrospinous ligament fixation for vaginal prolapse, for example, tend to compress and injure the nerve.
4.Diagnosis
4.1 Diagnostic criteria.
(1) The pain is distributed in the innervation area of the pubic nerve;
(2) The pain is further worsened in sitting position;
(3) The patient does not wake up with pain at night;
(4) No sensory loss on physical examination;
(5) The pain is improved by the pubic nerve block.
Exclusion criteria include paroxysmal sacrococcygeal, gluteal, or lower abdominal pain with pruritus or with abnormal imaging findings.
The difficulty in diagnosis is that all of these criteria are entirely subjective sensations and there is also a placebo effect or a false positive result of distal anesthesia with nerve blocks.
5. Treatment
5.1 Conservative treatment
Conservative therapy includes behavioral changes such as avoidance of triggering behaviors (bicycling, hip flexion, etc.). Stretching exercises can reduce pain in a proportion of patients with pubic neuralgia such as cyclists. Actions such as bending over and touching the toes or holding the knees toward the chest in the supine position are effective Acupuncture is effective for some patients, but not overall. Low back massage may be effective. Medications such as gabapentin (an antiepileptic) and tricyclic antidepressants are mostly ineffective. If conservative treatment is not effective, invasive treatment is available.