Pudendal nerve

The pudendal nerve arises from the S2-4 nerve roots of the anterior division of the sacral plexus. It is the nerve of the perineum and pelvic floor.

Gross anatomy

Origin

The pudendal nerve arises from the anterior division of ventral rami of 2nd, 3rd and 4th sacral nerves of the sacral plexus.

Course

The nerve emerges from the pelvis and courses through the gluteal region through the greater sciatic foramen, below the piriformis muscle. It then turns forward around the sacrospinous ligament and leaves the gluteal region through the lesser sciatic foramen (between sacrotuberous and sacrospinous ligaments). It is then directed into the pudendal canal, which lies on the obturator fascia above the falciform ridge on the ischial tuberosity.

Within the pudendal canal the nerve divides into:

• the inferior rectal nerve which is given off at the posterior end of the canal before the pudendal nerve continues and divides into two terminal branches:
• dorsal nerve of penis or clitoris
• perineal nerve

Both terminal branches then enter the deep perineal pouch above and below the internal pudendal artery, respectively.

The inferior rectal branch arches through the ischioanal fossa and reaches the perianal skin, as well as the external anal sphincter, supplying both.

The dorsal nerve of penis/clitoris accompanies the dorsal artery to supply the clitoris or skin of the penis. It gives no branches in the deep pouch.

The perineal branch gives off motor branches to superficial and deep perineal muscles and to the external urethral sphincter.

Relations

• passes below lower border of piriformis muscle as it passes through greater sciatic foramen
• lies on sacrospinous ligament just medial to spine of ischium as it passes through lesser sciatic foramen
• travels through pudendal canal with internal pudendal vessels

Variant anatomy

• contributions from S1 or S5 nerve roots
• inferior rectal nerve can come directly from sacral plexus or divide proximal to pudendal canal
• nerve plexus created by branches from inferior rectal and perineal nerves can form in ischiorectal fossa to supply external anal sphincter
• additional "accessory rectal nerve" from medial aspect of pudendal nerve at the level of sacrotuberous and sacrospinous ligaments which travels distally to perineum and levator ani