A 45-year-old presents with sudden onset of right homonymous hemianopia with macular sparing. MRI shows a lesion in the left occipital lobe. The macular sparing is best explained by:
- A The macular cortical representation in the occipital pole has dual blood supply from both posterior cerebral and middle cerebral arteries ✓
- B The macula has bilateral representation in both occipital cortices
- C The macula has a larger cortical representation that is more anterior in the calcarine cortex
- D Macular fibres cross at the optic chiasm bilaterally
Correct answer: A. The macular cortical representation in the occipital pole has dual blood supply from both posterior cerebral and middle cerebral arteries
Explanation
Macular sparing in occipital lobe lesions (most commonly PCA territory infarcts) is attributed to the dual blood supply of the occipital pole (macular cortex): the posterior cerebral artery primarily supplies the occipital cortex, but the macular cortex at the tip of the occipital pole also receives collateral supply from branches of the middle cerebral artery, making it more resistant to PCA territory infarction. An alternative theory involves bilateral cortical representation of the macular region.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.