A posterior cerebral artery (PCA) stroke most characteristically causes which deficit?

• A. Motor weakness of the face
• B. Speech disturbance
• C. Visual deficit (homonymous hemianopsia)
• D. Ataxia

Answer: (C)

Damage to the occipital cortex from a posterior cerebral artery stroke disrupts the brain’s processing of the opposite visual field. This leads to a contralateral homonymous hemianopia—loss of vision in the same half of the visual field in both eyes. The macula often shows sparing or variable involvement because the central vision can receive dual blood supply from nearby vessels, but the classic finding is the opposite-field visual deficit. In contrast, motor weakness of the face points to a middle cerebral artery issue affecting motor pathways, speech disturbances are typically from dominant-hemisphere MCA involvement, and ataxia suggests cerebellar or brainstem/cerebellar pathways—territories not characteristically supplied by the PCA. Thus, the hallmark deficit of a PCA stroke is a visual field defect—contralateral homonymous hemianopia.