Middle cerebral artery
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. 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 optic chiasm. It runs along the sylvian fissure up to the limen insulae, 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).
MCA was studied by Gunnal et al., in detail and classified it in four different types as bifurcated, trifurcated, quadrifurcated MCA and MCA with no trunks or single main trunk as per the termination 5).
Kahilogullari et al. proposed a way of classification made in relation to the terminology of the intermediate trunk, which is still a subject of debate. The intermediate trunk was present in 61% of cadavers and originated from a superior trunk in 55% and from an inferior trunk in 45%. Cortical branches supplying the motor cortex (precentral, central, and postcentral arteries) significantly originated from the intermediate trunk, and the diameter of the intermediate trunk significantly increased when it originated from the superior trunk. In measurements of the angles between the superior and intermediate trunks, it was found that the intermediate trunk had significant dominance in supplying the motor cortex as the angle increased. The intermediate trunk was classified into 3 types based on the angle values and the distance to the bifurcation point as Group A (pseudotrifurcation type), Group B (proximal type), and Group C (distal type). Group A trunks were seemingly closer to the trifurcation structure that has been reported on in the literature and was seen in 15%. Group B trunks were the most common type (55%), and Group C trunks were characterized as the farthest from the bifurcation point. Group C trunks also had the smallest diameter and fewest cortical branches. Similarities were found between the angles in cadaver specimens and on 3D CT cerebral angiography images. Beyond the separation point of the MCA, trunk structures always included the superior trunk and inferior trunk, and sometimes the intermediate trunk.
Interrelations of these vascular structures and their influences on the cortical branches originating from them are clinically important. The information presented in this study will ensure reliable diagnostic approaches and safer surgical interventions, particularly with MCA selective angiography 6).
The MCA territory was divided into 12 areas: orbitofrontal, prefrontal, precentral, central, anterior parietal, posterior parietal, angular, temporo-occipital, posterior temporal, middle temporal, anterior temporal, and temporopolar. The smallest cortical arteries arose at the anterior end and the largest one at the posterior end of the Sylvian fissure. The largest cortical arteries supplied the temporo-occipital and angular areas 7).
Three distinct patterns of perforators arising from the proximal middle cerebral artery were found 8).
Marinković et al., divided it into medial, middle, and lateral groups. Those in the medial group usually arose directly from the MCA main trunk close to the carotid bifurcation. There were usually three vessels in the middle group, which originated not only from the MCA trunk, but also from the MCA collateral (cortical) branches. Common stems, when present, gave rise to individual perforating vessels and occasionally to thin olfactory and insular rami. Perforating arteries in the lateral group varied from one to nine in number. In addition to an origin from the MCA trunk, they also arose from cortical branches supplying the frontal and temporal lobes. The fact that lateral perforating vessels often originated from division sites and from terminal branches of the MCA is of clinical significance, because aneurysms are more commonly located at the MCA bifurcation. Anastomoses were not found among the perforating arteries. In two specimens, a fusion between a perforating artery and the MCA trunk was noted. Since the perforating vessels are obviously end arteries, injury to them must be avoided during operations for MCA aneurysms 9).