What nerve roots supply the perineum?

From the Guidelines

The perineum is primarily supplied by the sacral nerve roots S2, S3, and S4, which form the pudendal nerve. These nerve roots are crucial for the innervation of the urinary and anal sphincters, as well as the perineal floor 1. The pudendal nerve provides sensory innervation to the external genitalia and motor innervation to the external anal sphincter, external urethral sphincter, and muscles of the perineal floor. Some key points to consider about the innervation of the perineum include:

• The sacral nerve roots S2-S4 are responsible for the innervation of the perineum 1
• The pudendal nerve arises from these nerve roots and travels through the greater sciatic foramen, around the sacrospinous ligament, and through the pudendal canal (Alcock's canal) to reach the perineum
• The perineum also receives innervation from other sources, including the posterior femoral cutaneous nerve (S2-S3), ilioinguinal nerve (L1), and genitofemoral nerve (L1-L2) Understanding the innervation pattern of the perineum is essential for various medical procedures and diagnoses, including regional anesthesia, diagnosis of perineal pain syndromes, and comprehension of the neurological effects of pelvic trauma or surgery.

From the Research

Nerve Roots Supplying the Perineum

The perineum is supplied by several nerve roots, primarily originating from the sacral region of the spine.

• The pudendal nerve, which is often considered the primary nerve responsible for the innervation of the perineum, originates from the S3 root, and sometimes from the S2 and S4 roots as well 2, 3.
• The pudendal nerve is responsible for the sensory innervation of the skin of the perineum, including the glans penis, clitoris, scrotum, and labia majora, as well as the motor innervation of the erector muscles and the striated sphincters 2.
• The perineal nerve, a branch of the pudendal nerve, also plays a role in the innervation of the perineum, particularly the anterior part of the perineum and the posterior surface of the scrotum, and is derived from the S2-S3-S4 sacral nerve roots 3.
• Other nerves, such as the levator ani nerve, may also contribute to the innervation of the pelvic floor muscles, including those in the perineum, although their specific role and relationship to the pudendal nerve is still being researched 4.