Most of the authors who have carried out anatomical studies of the middle cerebral artery agree on this being one of the least variable arteries. Nevertheless, they describe early bifurcation, trifurcation, quadrifurcation, duplication, single non-bifurcating trunk, hypoplasia, fenestrations, etc. The middle cerebral artery is one of the longest intracranial arteries, considered to be having one of the most extensive irrigation territories in the brain. The artery arises below the anterior perforated substance, lateral to the optical chiasm. It runs along the sylvian fissure up to the limen insula, where it bends at an angle which can be upto 90° and it is at that point where the bifurcation usually occurs.
The MCA arises from the internal carotid artery and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex. It also supplies blood to the anterior temporal lobes and the insula. The artery supplies a portion of the frontal lobe and the lateral surface of the temporal and parietal lobes, including the primary motor and sensory areas of the face, throat, hand and arm, and in the dominant hemisphere, the areas for speech.
The left and right MCAs rise from trifurcations of the internal carotid arteries and thus are connected to the anterior cerebral artery and the posterior communicating artery, which connect to the posterior cerebral artery. The MCAs are not considered a part of the Circle of Willis.
The angular artery is a significant terminal branch of the anterior or middle trunk of the middle cerebral artery (MCA).
The MCA is divided into M1, M2, M3 and M4 segments:
It is worth emphasizing that the nomenclature ‘M’ that designates the segments in which the middle cerebral artery is divided –proximal, pre-bifurcation: M1; post-bifurcation: M2, and beyond: M3 and M4, is derived from an angiographic study with anatomical correlation carried out by a Uruguayan neuroradiologist (Prof. N. Azambuja), who divided the artery in the segments whose denomination is used worldwide nowadays. As they were described in Montevideo (Uruguay), he used the first letter of the city where he developed his study. Since it coincides with “media” (middle, in English) named thus after the middle cerebral artery, the nomenclature was extended to the anterior cerebral artery, and in this case it is referred to as segment A1…
The middle cerebral artery is the artery most often occluded in stroke.
Anatomical variations of the middle cerebral artery (MCA) are an important clinical issue, due to high prevalence of intracranial aneurysms. Anatomical variations of vessels can lead to higher shear stress, which is thought to be the main factor leading to aneurysm formation and consequently to higher prevalence of aneurysms.
The most common configuration of MCA is bifurcation before the genu with no dominating post-division trunk. Incidence of MCA aneurysms is not correlated with anatomical variations of MCA and the circle of Willis 2).