Middle cerebral arteryMiddle cerebral artery and its branches (patient has a hypoplastic A1 segment and an absent PCOM, resulting in a purely MCA angio from internal carotid artery injection)
The middle cerebral artery divides into four segments, named by the region they supply as opposed to order of branching as the latter can be somewhat variable:[2]
M1: Thesphenoidal segment (stem),[3] receiving its name due to its course along the adjacentsphenoid bone. It is also referred to as thehorizontal segment, though this may be misleading since the segment may descend, remain flat, or extend posteriorly the anterior (dorsad) in different individuals. The M1 segment perforates the brain with numerousanterolateral central (lateral lenticulostriate) arteries, which supply thebasal ganglia.
M2: Extending anteriorly on theinsula, this segment is known as theinsular segment. It is also known as theSylvian segment when theopercular segments are included. The MCA branches maybifurcate or sometimestrifurcate into trunks in this segment which then extend into branches that terminate towards the cortex.
M3: Theopercular segment, extending laterally and exteriorly from the insula towards the cortex. This segment is sometimes grouped with M2.
M4: These finerterminal orcortical segments irrigate the cortex. They begin at the external margins of the Sylvian fissure and extend distally away on the cortex of the brain.
TheM2 andM3 segments may each split into 2 or 3 main trunks (terminal branches) with anupper trunk,lower trunk and occasionally amiddle trunk. Bifurcations and trifurcations occurs in 50% and 25% of the cases respectively. Other cases include duplication of the MCA at theinternal carotid artery (ICA) or an accessory MCA (AccMCA) which arise not from the ICA but as a branch from the anterior cerebral artery.[4] Themiddle trunk that exist in parts of the population, when present provides thepre-Rolandic,Rolandic,anterior parietal,posterior parietal and theangular artery for irrigation instead of theupper andlower trunks.
The branches of the MCA can be described by the areas that they irrigate.
Lateral frontobasal (orbitiofrontal): This artery branches out anteriorly, superiorly and laterally to vascularize the inferior frontal gyrus. It "competes" in size with thefrontal polar branch of theanterior cerebral artery
Prefrontal arteries: These arteries fan out over the insula and exit to the cortex via the medial surface of the frontaloperculum. The arteries fan superiorly over thepars triangularis and vascularize the inferior and middle frontal gyrus. Near the superior frontal gyrus these arteriesanastomose with branches from thepericallosal artery of the anterior cerebral artery.
Pre-Rolandic artery (precentral): The artery extends out on the medial surface of the operculum and supplies the posterior parts of the middle and inferior frontal gyri as well as the lower parts of the pre-central gyrus. This artery branches once or twice and is relatively invariant across anatomies.
Rolandic arteries (central): The artery extends out and exits from the central portion of the operculum then passes inside the central sulcus. This artery bifurcates in 72% of individuals and irrigates the posterior pre-central gyrus and the inferior portion of the post-central gyrus.
Anterior parietal: This artery usually originates from a distal MCA branch. In some cases it branches from the rolandic artery or from the posterior parietal artery. It extends the length of interparietal sulcus and descends slightly posteriorly.
Posterior parietal: Emerges from the posterior end of the Sylvian fissure and extends first posteriorly, and then anteriorly along the posterior of the parietal lobe. It also branches to the supramarginal gyrus.
Angular: The angular artery is a significant terminal branch of the anterior or middle trunk of the MCA. It emerges from the Sylvian fissure and passes over the anterior transverse temporal gyrus and usually divides into two branches. One of the branches supplies theangular gyrus while the other supplies the supramarginal gyrus, posterior superior temporal gyrus, and the parietooccipital arcus (sulcus).
Temporooccipital: The longest cortical artery, it runs posteriorly opposite to the center of the operculum. Upon its exit from the Sylvian fissure, it runs parallel to the superior temporal sulcus and supplies the superior and inferior occipital gyri. This vessel anastamoses with the posterior cerebral artery and may exist as one or two arteries, 67% or 33% of the time, respectively.
Temporopolar: The artery extends from the sphenoidal segment of the MCA via the inferior surface of the operculum and supplies the polar and anterior lateral portions of the temporal lobe. The vessel can be identified in 52% of normal angiograms
Anterior temporal: This artery typically arises from the proximal MCA trunk and extends in the similar fashion as thetemporopolar artery and vascularizes the same regions.
Middle temporal: This artery extends from the Sylvian fissure opposite to the inferior frontal gyrus and supplies superior and middle portions of the middle temporal lobe. It can be identified in 79% of angiograms.
Posterior temporal: This artery extends out and away from the operculum and turns in a step-wise manner first inferiorly then posteriorly into the superior temporal sulcus then to the middle temporal sulcus. This vessel supplies posterior portion of the temporal lobe and is the origin of several perforating arteries that irrigate the insula. It is readily identifiable in most radiograms.
Paralysis (-plegia) or weakness (-paresis) of the contralateral face and arm (faciobrachial)
Sensory loss of the contralateral face and arm.
Damage to the dominant hemisphere (usually the left hemisphere) results in aphasia (i.e.Broca's area orWernicke's)
Damage to the non-dominant hemisphere (usually the right hemisphere) results in contralateralneglect syndrome, inaccurate localization in the half field, impaired ability to judge distance (nondominant parietal lobe).
Large MCA infarcts often havedéviation conjuguée, a gaze preference towards the side of the lesion, especially during the acute period. Contralateralhomonymous hemianopsia is often present.
