A patient with a right middle cerebral artery (MCA) infarct has left hemiplegia, left hemianesthesia, and left homonymous hemianopia (visual field defect). The homonymous hemianopia is due to involvement of which structure in the MCA territory?

• A Right optic nerve
• B Optic chiasm
• C Optic radiations (parietal and temporal lobe components) in the right hemisphere ✓
• D Left calcarine cortex

Explanation

The optic radiations (geniculocalcarine tract) travel through the posterior limb of the internal capsule, parietal lobe (upper fibers for lower visual field), and temporal lobe (Meyer's loop, lower fibers for upper visual field) before reaching the calcarine cortex. All these are within the MCA territory. A right MCA infarct involving the optic radiations causes left homonymous hemianopia. The calcarine cortex itself is supplied by the posterior cerebral artery (PCA). The optic chiasm is supplied by branches of the anterior communicating and anterior cerebral arteries. A right optic nerve lesion causes right monocular blindness, not a hemianopia.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.