Why does a homonymous hemianopia caused by a posterior cerebral artery infarct often show macular sparing?

• A The macula has double representation in both cerebral hemispheres
• B The posterior cerebral artery supplies the entire primary visual cortex
• C Macular ganglion cells project bilaterally through the chiasm
• D The foveal representation at the occipital pole receives collateral supply from the middle cerebral artery ✓

Explanation

The foveal (macular) representation lies at the most posterior tip of the occipital cortex, at the border zone between middle and posterior cerebral artery territories. Collateral flow from the MCA often preserves this tip when the PCA is occluded, producing macular sparing. The older teaching of bilateral macular representation (option A) is now considered less important, though it still appears as a distractor. Retinal ganglion fibres decussate fully at the chiasm, not partially, ruling out option C.

Reference: Gray's Anatomy for Students, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.