The perineal nerve (S2-4) is a nerve of the pelvic region and the largest terminal branch of the pudendal nerve.
It supplies motor innervation to the perineal muscles as well as contributing to the sensory supply of the perineum.
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The perineal nerve arises from the pudendal nerve within the pudendal canal – a passageway within in the lateral wall of the ischioanal fossa.
After leaving the pudendal canal, the perineal nerve continues for another 2-3cm (acccompanied by the perineal artery) and then terminates by dividing into into two branches:
- Superficial perineal nerve – gives rise to posterior scrotal/labial sensory branches.
- Deep perineal nerve – supplies motor innervation to the perineal muscles and sensation to the vestibule and inferior vagina.
Fig 1
The perineal nerve arises from the pudendal nerve within the pudendal canal.
Sensory Functions
The perineal nerve supplies cutaneous sensation via its two main branches:
- Superficial perineal nerve – gives rise to posterior scrotal/labial sensory branches.
- In males, supplies the skin of the perineum and posterior scrotum
- In females, supplies the skin of the labia minora and majora
- Deep perineal nerve – supplies the sensation to the vestibule and inferior vagina in females.
Fig 2
The perineal nerve supplies sensation to the labia, vestibule and inferior vagina in females.
Motor Functions
The deep branch of the perineal nerve provides motor innervation to the perineal muscles:
- Bulbospongiosus
- Ischiocavernosus
- Superficial transverse perineal muscle
- External urethral sphincter
- Levator ani muscle