From the Research
The Middle Cerebral Artery (MCA) is divided into four main segments: M1 through M4, as described in the most recent and highest quality study available 1. The M1 segment is the horizontal portion that extends from the internal carotid artery bifurcation to the sylvian fissure. The M2 segment consists of the branches that travel through the sylvian fissure over the insular cortex. The M3 segment includes the branches that emerge from the sylvian fissure and travel over the brain's surface. Finally, the M4 segment refers to the terminal cortical branches that supply the lateral cerebral cortex. Functionally, the MCA can also be divided into superior and inferior trunks after the M1 segment, with the superior trunk supplying the frontal and parietal lobes, while the inferior trunk supplies the temporal lobe. These divisions are important clinically because occlusions at different segments produce distinct stroke syndromes, with proximal occlusions causing more extensive deficits than distal ones. Understanding these divisions helps clinicians localize lesions and predict functional outcomes in patients with cerebrovascular events, as supported by studies on mechanical thrombectomy and intravenous thrombolysis in acute ischemic stroke patients 2, 3, 4, 5. Some key points to consider include:
- The MCA territory is divided into 12 areas, including orbitofrontal, prefrontal, precentral, central, anterior parietal, posterior parietal, angular, temporo-occipital, posterior temporal, middle temporal, anterior temporal, and temporopolar areas 1.
- The smallest cortical arteries arise at the anterior end and the largest one at the posterior end of the Sylvian fissure 1.
- The relationship of each of the cortical arteries to a number of external landmarks is crucial for understanding the anatomy of the MCA and its divisions 1. However, the most recent study on the topic, which is from 1981 1, provides the most accurate description of the MCA divisions, and its findings should be prioritized in clinical practice.