A 65-year-old man with left-sided weakness has a sudden onset focal neurologic deficit. Which artery is most likely occluded?

• A. Middle cerebral artery
• B. Anterior cerebral artery
• C. Posterior cerebral artery
• D. Basilar artery

Answer: (A)

Sudden focal neurologic deficits from an artery blockage usually reflect Brain region-specific loss of function. The middle cerebral artery runs along the lateral surface of the hemisphere and supplies the primary motor cortex areas that control the face and arm. When this artery is occluded, the resulting deficit is contralateral weakness most noticeable in the face and arm, which fits a left-sided weakness caused by a right hemispheric lesion. Among the major arteries, this pattern is the most common cause of focal motor stroke.

Occlusion of the anterior cerebral artery tends to cause weakness more in the leg and often frontal-lobe behavioral changes, not the classic face/arm-dominant weakness. The posterior cerebral artery affects the occipital and temporal lobes, so visual field losses and higher-level sensory or cognitive deficits are more typical. Basilar artery blockage disrupts brainstem function, producing cranial nerve deficits, ataxia, or altered consciousness rather than isolated unilateral weakness.