The pudendal nerve is a significant paired nerve in the pelvic region, playing a role in sensation and movement. Understanding its location and pathway is fundamental to comprehending its influence on bodily functions, from basic controls to complex sensations.
Anatomy and Path of the Pudendal Nerve
The pudendal nerve originates from the sacral plexus, a network of nerves formed by the ventral rami of the second, third, and fourth sacral spinal nerves (S2-S4). After its formation, the nerve descends within the pelvic cavity, positioned near the lateral wall. It is closely associated with the internal pudendal artery and vein throughout much of its path.
The nerve then exits the pelvis through the greater sciatic foramen, passing below the piriformis muscle into the gluteal region. It curves around the posterior aspect of the sacrospinous ligament, which connects the sacrum to the ischial spine.
The pudendal nerve then re-enters the pelvis through the lesser sciatic foramen, an opening separated from the greater sciatic foramen by the sacrospinous ligament. Upon re-entry, the nerve continues its course within Alcock’s canal, also known as the pudendal canal. This fibrous tunnel, formed by a duplication of the obturator internus muscle fascia, provides a protective sheath as the nerve runs anterosuperiorly toward the pubic symphysis.
Branches and Their Innervation
As the pudendal nerve travels through Alcock’s canal, it divides into three main terminal branches, each responsible for innervating specific structures in the pelvic region.
The first branch is the inferior rectal nerve. It courses medially through the ischioanal fossa, providing motor innervation to the external anal sphincter for voluntary defecation control. It also carries sensory information from the anal canal below the pectinate line and the perianal skin, including pain sensations.
Next, the perineal nerve branches off. This branch divides into deep (muscular) and superficial (cutaneous) perineal nerves. The deep perineal nerve supplies motor innervation to the muscles of the urogenital triangle, including the bulbospongiosus, ischiocavernosus, superficial transverse perineal muscles, and the external urethral sphincter for voluntary urination control. The superficial perineal nerve provides sensory innervation to the skin of the perineum, the labia minora and majora in females, and the posterior scrotum in males.
The third main branch is the dorsal nerve of the clitoris (females) or penis (males), a purely sensory branch. This nerve runs along the shaft and glans, transmitting sensations of touch, pleasure, and pain, playing a role in sexual arousal and erection.
Functions of the Pudendal Nerve
The pudendal nerve performs several functions, encompassing sensory, motor, and autonomic roles within the pelvic region.
Its sensory function provides feeling to the external genitalia, perineum, and anal canal, essential for everyday sensations and sexual arousal.
Its motor function controls pelvic floor muscles, including the external anal sphincter for voluntary bowel control and the external urethral sphincter for voluntary bladder control.
The nerve also contributes to autonomic functions, particularly sexual response. For example, the dorsal nerve of the penis or clitoris influences vasodilation of erectile tissue. This integrated function coordinates muscles and sensations for continence and sexual activity.
Common Conditions Related to the Pudendal Nerve
Dysfunction or damage to the pudendal nerve can lead to various symptoms, with pudendal neuralgia being one of the most recognized conditions. Pudendal neuralgia is characterized by chronic neuropathic pain in the pelvic region, specifically in areas supplied by the nerve like the perineum, buttocks, or genitals. The pain is often described as burning, stabbing, aching, or tingling, and it frequently worsens with sitting.
Various factors can cause pudendal nerve dysfunction or entrapment. Common causes include nerve compression, particularly within Alcock’s canal or between the sacrospinous and sacrotuberous ligaments. Trauma, such as injuries from falls, difficult childbirth, or pelvic surgical procedures, can also damage the nerve.
Repetitive strain from activities like prolonged cycling can also lead to pudendal nerve irritation, sometimes called “cyclist’s syndrome.” Other causes include chronic constipation (leading to straining) or benign growths. Patients might also experience associated symptoms like sexual dysfunction or issues with bladder and bowel control.