Which Artery Occlusion Is Most Likely to Cause Hemiplegia?

The Role of Cerebral Blood Supply in Stroke and Hemiplegia

Understanding the vascular anatomy of the brain is crucial when identifying which artery occlusion is most likely to lead to hemiplegia—a condition characterized by paralysis on one side of the body. The brain receives its blood supply primarily through two major systems: the internal carotid artery system and the vertebrobasilar artery system. While both play vital roles, it's the internal carotid system that supplies approximately the anterior three-fifths of the cerebrum, including critical regions such as the frontal lobe, temporal lobe, parietal lobe, and basal ganglia.

The Internal Carotid System and Its Clinical Significance

Occlusions within the internal carotid artery system are particularly dangerous, often resulting in large-scale cerebral infarctions due to the extensive territory they perfuse. Among the various branches of this system, the middle cerebral artery (MCA) stands out as the vessel whose blockage most commonly leads to severe neurological deficits—especially contralateral hemiplegia.

Why the Middle Cerebral Artery Is a Key Culprit

The MCA is responsible for delivering oxygenated blood to a vast portion of the cerebral hemisphere, specifically the anterior two-thirds of the lateral surface of the brain. This includes essential areas such as the right frontal, parietal, temporal lobes, and the insular cortex. Given its broad distribution, any interruption in blood flow through the MCA can have devastating consequences.

Deep Perforating Branches and Their Impact on Motor Function

One of the most clinically significant aspects of the MCA is its deep penetrating branches, which supply critical motor pathways located in the internal capsule—particularly the genu and the anterior two-thirds of the posterior limb. These regions house corticospinal tracts that control voluntary movement on the opposite side of the body. When an occlusion occurs in these small but vital arteries, the result is often sudden and profound weakness or complete paralysis of the face, arm, and leg—classic signs of hemiplegia.

Potential Complications Beyond Motor Deficits

Beyond physical disability, MCA infarcts can lead to additional serious complications. Patients may experience rapid deterioration in consciousness, confusion, or even fall into a coma, especially if the infarct involves a large brain area or causes significant cerebral edema. Aphasia is also common in dominant hemisphere involvement, while visuospatial neglect may occur if the non-dominant side is affected.

In summary, while multiple cerebral arteries can contribute to stroke-related paralysis, the occlusion of the middle cerebral artery remains the most frequent and impactful cause of hemiplegia. Early recognition of symptoms—such as facial droop, arm drift, and speech difficulties—is essential for prompt intervention, potentially minimizing long-term disability through timely thrombolytic therapy or endovascular treatment.