The pudendal nerve is a major nerve of the pelvis, functioning as the primary neurological connection to the perineum and external genitalia. This paired nerve arises from the sacral plexus, a network of nerves in the lower spinal column. Specifically, the pudendal nerve is formed by the ventral rami of the spinal nerves S2, S3, and S4.
Its name is derived from the Latin word pudendum, which refers to the external genitalia. The nerve exits the pelvis through the greater sciatic foramen, wraps around the sacrospinous ligament, and re-enters through the lesser sciatic foramen. It is classified as a mixed nerve because it transmits both motor signals (controlling muscle movement) and sensory signals (conveying touch, temperature, and pain). This dual function makes it integral to a range of bodily functions, including voluntary control over continence and sexual response.
Motor Functions and Muscle Control
The motor component of the pudendal nerve controls several striated (skeletal) muscles in the pelvic floor and perineum, providing conscious command over functions often assumed to be automatic. The nerve supplies the external anal sphincter, allowing a person to voluntarily tighten the muscle to prevent the release of feces. Similarly, a branch of the pudendal nerve controls the external urethral sphincter, the muscle that permits voluntary holding or releasing of urine. The ability to prevent accidental leakage is directly attributable to the nerve’s motor axons. Without this voluntary input, the body would rely solely on involuntary reflexes, leading to incontinence.
The nerve also innervates other key muscles of the pelvic floor, including the ischiocavernosus and bulbospongiosus muscles. These muscles are involved in both pelvic stability and sexual function. For example, in males, the bulbospongiosus muscle assists in stiffening the penis and expelling semen during ejaculation.
The nerve also contributes motor fibers to the levator ani, a broad sheet of muscle that provides structural support for pelvic organs like the bladder and uterus. This motor control over the perineal muscles is fundamental to both continence and sexual response.
Sensory Functions of the Perineum and Genitalia
The sensory role of the pudendal nerve maps feeling across the perineum and external genitalia. This sensation is carried through three primary terminal branches. The inferior rectal nerve is the first branch, which provides sensation to the skin around the anus and the lower part of the anal canal.
The perineal nerve, the next branch, provides sensation to the skin of the perineum, the area between the anus and the scrotum or vulva. This nerve further divides into posterior scrotal nerves (males) or posterior labial nerves (females), supplying feeling to the scrotum and labia. This branch handles general touch and temperature sensation in the urogenital triangle.
The final branch is the dorsal nerve of the penis (males) or the dorsal nerve of the clitoris (females). This branch carries sensory information from the skin of the external genitalia, including the shaft and glans. The dorsal nerve is responsible for the sensory component of sexual arousal and response.
When Innervation Fails: Pudendal Nerve Dysfunction
When the pudendal nerve is damaged, irritated, or compressed, the consequences manifest as a range of motor and sensory dysfunctions in the innervated areas. One of the most common conditions is pudendal neuralgia, which involves chronic, sharp, burning, or shooting pain felt in the perineum, rectum, or genitals. This neuropathic pain is often described as being worse when sitting, as the seated position can compress the nerve against ligaments or muscle, and is frequently relieved by standing or lying down.
The motor deficits resulting from nerve compromise often lead to functional problems with continence. Damage to the motor fibers controlling the sphincters can result in urinary incontinence or fecal incontinence, which is the involuntary loss of control over bowel movements. Patients may also report a feeling of incomplete emptying of the bladder or rectum, or a sensation that a foreign object is present internally.
Sexual dysfunction is another significant consequence of failed pudendal nerve innervation due to both sensory and motor loss. In males, this can present as erectile dysfunction or loss of sensation in the penis. In females, it may involve decreased genital sensation, persistent genital arousal disorder, or pain during sexual activity.
Common causes of pudendal nerve dysfunction include trauma sustained during childbirth, especially due to stretching or compression. Activities involving prolonged, repetitive pressure on the perineum, such as long-distance cycling or horseback riding, can also cause nerve irritation, leading to a condition sometimes called “cyclist’s syndrome.” Non-invasive treatment approaches often focus on relieving pressure and addressing underlying muscle issues, including lifestyle modifications and specialized pelvic floor physical therapy.