A 55-year-old woman has intermittent involuntary twitching of the left orbicularis oculi progressing over two years to involve all muscles on the left half of her face, with brief sustained spasms triggered by voluntary movement. MRI angiography shows vascular contact at the root exit zone of the facial nerve. Which vessel is MOST commonly implicated?

• A Superior cerebellar artery
• B Anterior inferior cerebellar artery ✓
• C Posterior cerebral artery
• D Basilar artery trunk

Explanation

Hemifacial spasm is caused by pulsatile vascular compression of the facial nerve at its root entry zone at the pontomedullary junction, and the anterior inferior cerebellar artery is the most commonly implicated vessel, with the posterior inferior cerebellar artery and vertebral artery also reported. The superior cerebellar artery is the usual culprit in trigeminal neuralgia, which kills option A, and the basilar trunk and PCA are uncommon offenders here.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.