Middle Cerebral Artery (MCA)
The middle cerebral artery (MCA) is the most commonly occluded vessel in patients presenting with unilateral facial asymmetry combined with arm and leg weakness. This clinical presentation represents the classic anterior circulation stroke syndrome affecting the MCA territory 1.
Clinical Reasoning
The combination of unilateral facial droop with ipsilateral arm and leg weakness localizes to the anterior circulation, specifically the MCA territory 1. According to the European Society of Cardiology, focal neurological symptoms from carotid atherosclerotic disease most commonly manifest as motor deficits involving the hand, arm, and face together, or more rarely including the leg 1. This distribution reflects the homuncular representation in the motor cortex supplied by the MCA 1.
Why MCA and Not Other Vessels
The MCA supplies the lateral cerebral cortex, including the motor and sensory strips for the face and upper extremity, with variable involvement of the lower extremity depending on the extent of infarction 2, 3. The clinical presentation described—face, arm, and leg weakness together—indicates involvement of the motor cortex and/or subcortical structures supplied by the MCA 1.
Posterior circulation strokes (vertebrobasilar system) would present differently with ataxia, cranial nerve deficits, visual field loss, dizziness, imbalance, and incoordination rather than the classic face-arm-leg weakness pattern 4. The vertebrobasilar system supplies the brainstem, cerebellum, and occipital lobes, not the motor cortex 4.
Stroke Mechanisms in MCA Disease
Atherothromboembolism
Most symptoms from carotid atherosclerotic disease arise from plaque inflammation and disruption with subsequent embolism of locally formed thrombus or plaque debris, leading to occlusion of cerebral arteries in the anterior circulation 1. This athero-thromboembolism is the predominant mechanism 1.
Progressive Evolution
MCA occlusive disease characteristically shows progressive neurologic deterioration over days to weeks rather than acute onset 2. This "stuttering stroke" pattern results from thrombus propagation and may be associated with symptom progression over hours to days 1.
Hemodynamic Mechanism
With high-grade stenosis or complete occlusion, cerebral ischemia may also arise from flow reduction (hemodynamic mechanism), particularly when collateral circulation through the circle of Willis is inadequate 1.
Common Pitfalls
Do not assume all face-arm-leg weakness is MCA territory—the specific distribution matters. Pure leg weakness suggests anterior cerebral artery (ACA) territory, while isolated hand weakness can occur with MCA branch occlusion 1.
Bilateral findings would suggest basilar artery occlusion with altered consciousness and involvement of multiple posterior circulation territories, not the focal unilateral presentation described 4.
MCA disease patients are more often younger, female, and Black compared to internal carotid artery disease patients, and they typically present with progressive deficits rather than acute onset 2.