A 64-year-old man with atrial fibrillation presents with sudden quadriplegia, lower cranial nerve palsies, and preserved vertical eye movements and blinking. He is fully conscious. MRI shows infarction of the basis pontis. Which vessel is occluded?

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

Explanation

Locked-in syndrome results from bilateral ventral pontine infarction due to basilar artery thromboembolism, destroying the corticospinal and corticobulbar tracts while sparing the reticular activating system and the oculomotor pathways, so consciousness and vertical eye movement are preserved. Posterior cerebral artery occlusion gives occipital infarction with visual field defects, not quadriplegia. Anterior spinal artery occlusion causes anterior cord syndrome below the lesion.

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

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