A 62-year-old man presents after a stroke with a right-sided homonymous SUPERIOR quadrantanopia. The lesion most likely involves which structure?

• A Left temporal lobe optic radiation (Meyer's loop) ✓
• B Right temporal lobe optic radiation (Meyer's loop)
• C Right parietal lobe optic radiation
• D Left parietal lobe optic radiation

Explanation

Meyer's loop sweeps through the temporal lobe and carries fibres representing the contralateral superior visual field, so a left temporal lobe lesion gives right superior quadrantanopia, classically described as pie in the sky. Parietal lobe lesions involve the superior bundle of optic radiations carrying the inferior field, giving inferior quadrantanopia instead. Because the defect is homonymous, the lesion must lie on the side opposite the affected field, eliminating both right-sided options.

Reference: Gray's Anatomy, 42nd ed.

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Written and medically reviewed by the StethoPrep medical team.