A 70-year-old woman suffers an infarct of the left primary visual cortex. She has a right homonymous hemianopia, yet when tested with small targets she retains central vision on the right. What anatomical feature accounts for this macular sparing?
- A Dual arterial supply of the occipital pole from the posterior cerebral and middle cerebral arteries ✓
- B Crossed representation of the macula in the lateral geniculate body
- C Decussation of macular fibres in the optic chiasma
- D Projection of the macula to the anterior calcarine cortex
Correct answer: A. Dual arterial supply of the occipital pole from the posterior cerebral and middle cerebral arteries
Explanation
The occipital pole, which represents the macula, receives its arterial supply from terminal branches of both the posterior cerebral artery and the middle cerebral artery via collateral anastomoses at the watershed zone. Occlusion of one posterior cerebral artery therefore spares the pole bilaterally supplied region, producing macular sparing. The macula is represented at the posterior pole of the calcarine cortex, not anteriorly, and chiasmal crossing concerns nasal retinal fibres, not macular preservation after cortical infarction.
Reference: Gray's Anatomy for Students, 4th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.