The pudendal nerve block is performed by injecting local anesthetic at the ischial spine. The pudendal nerve re-enters the perineum via which canal, and what compartment does it first enter?

• A Lesser sciatic foramen to enter directly into the superficial perineal pouch
• B Greater sciatic foramen to pass directly to the external urethral sphincter
• C Alcock's canal (pudendal canal) in the lateral wall of the ischiorectal (ischioanal) fossa; enters the ischioanal fossa before branching ✓
• D Obturator canal to innervate the perineal muscles from above

Explanation

After hooking around the ischial spine, the pudendal nerve passes through the lesser sciatic foramen and enters Alcock's canal (the pudendal canal), which is a fascial tunnel on the lateral wall of the ischiorectal (ischioanal) fossa formed by a splitting of the obturator fascia. Inside the canal, the pudendal nerve gives off the inferior rectal nerve, then the perineal nerve, and finally the dorsal nerve of the penis/clitoris. A pudendal nerve block at the ischial spine anesthetizes all these branches and is used in obstetric analgesia and perineal surgery.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.