From the Research
A successful pudendal nerve block eliminates the anal wink reflex. When the pudendal nerve is properly anesthetized, typically using 10-20 mL of local anesthetic (such as 0.5% bupivacaine or 1-2% lidocaine) injected at the pudendal canal or via a transvaginal or transperineal approach, sensory and motor function in the distribution of the pudendal nerve is temporarily blocked. The anal wink reflex, which is a contraction of the external anal sphincter in response to stroking or pinching the perianal skin, is mediated by the pudendal nerve through its inferior rectal branch. This reflex arc involves sensory fibers carrying the stimulus to the sacral spinal cord (S2-S4) and motor fibers returning to contract the external anal sphincter. When the pudendal nerve is blocked, both the afferent (sensory) and efferent (motor) components of this reflex are interrupted, resulting in absence of the anal wink.
This absence can be used clinically to confirm successful pudendal nerve blockade before proceeding with perineal procedures or to provide analgesia during childbirth, as supported by studies on the management of pudendal nerve entrapment syndrome 1 and the role of nerve blocks in diagnosing and treating pudendal neuralgia 2, 3, 4. Although the provided studies do not directly address the effect of pudendal nerve block on the anal wink reflex, the underlying anatomy and physiology of the pudendal nerve and its role in mediating the anal wink reflex support this conclusion. Additionally, a study on the effect of combined pudendal nerve and spermatic cord block on postoperative analgesia after posterior urethroplasty suggests the effectiveness of pudendal nerve blocks in managing pain in the perineal area 5.
Key points to consider include:
- The pudendal nerve plays a crucial role in mediating the anal wink reflex.
- A successful pudendal nerve block interrupts both the sensory and motor components of the reflex arc.
- The absence of the anal wink reflex can be used to confirm successful pudendal nerve blockade.
- Pudendal nerve blocks are a useful tool in managing pain in the perineal area, as supported by various studies 1, 2, 3, 4, 5.