A 66-year-old man has sudden bilateral blindness following a hypotensive episode. Pupillary reactions are normal and fundoscopy is unremarkable. Visual field testing months later reveals sparing of the central 5 degrees of vision on each side. Where is the lesion?

• A Optic nerves bilaterally
• B Lateral geniculate bodies bilaterally
• C Optic chiasma
• D Occipital cortex supplied by both posterior cerebral arteries ✓

Explanation

Cortical blindness with macular sparing localizes to bilateral primary visual cortex along the calcarine sulcus, usually after bilateral posterior cerebral artery infarction. Macular sparing occurs because the occipital pole representing the macula receives anastomotic supply from terminal branches of the middle cerebral artery, and because the large macular representation extends beyond the PCA territory. Normal pupils exclude optic nerve and chiasmal disease, since the afferent limb of the light reflex is intact distal to the lateral geniculate bodies.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.