Middle cerebral artery (MCA)

M1 - Horizontal segment

Extends from ICA bifurcation to the sylvian fissure. Runs under anterior perforated substance. Bi- or trifurcates before the sylvian fissure into trunks that turn upwards forming a curve, the MCA genu.

Branches:

1. Lateral lenticulostriate arteries
   • Perforating branches from M1 with very poor collateralization potential
   • Supply:
     • External capsule
     • Putamen
     • Globus pallidus
     • Head of nucleus caudatus (superior part)
     • Internal capsule

M2 - Insular segment

The M2 segment consists of the 2 or 3 arterial trunks that arise after the bi- or trifurcation of M1. These course superiorly along the surface of the insula to the top of the insula.

M3 - Opercular segment

From the top of the insula these segments turn inferolaterally and exit through the sylvian fissure.

M4 - Cortical segment

These segments run from the sylvian fissure and supply branches over the lateral surface of the hemisphere.

Named cortical branches:

1. Frontal opercular artery
   • Arises from the superior division of the MCA
   • Emerges from the Sylvian fissure, traveling over the frontal operculum
   • Supplies:
     • Inferior frontal gyrus

2. Lateral orbitofrontal (lateral frontobasal) artery
   • Arises most often from the superior division of the MCA
   • Passes anteriorly on the inferolateral part of the frontal lobe.
   • Supplies:
     • Orbital gyri
     • Inferior frontal gyrus

3. Prefrontal (anterior frontal) artery
   • Arises from the superior division of the MCA
   • Exit the sylvian fissure over the medial surface of the frontal operculum
   • Supply:
     • Inferior frontal gyrus
     • Middle frontal gyrus

4. Precentral (prerolandic) artery
   • Arises from the superior division of the MCA
   • Extends out on the medial surface of the operculum
   • Supplies:
     • Posterior parts of the middle and inferior frontal gyri
     • Inferior parts of the precentral gyrus

5. Central sulcus (rolandic) artery
   • Arises from the superior division of he MCA
   • Exits from the central portion of the operculum. Runs inside the central sulcus.
   • Supplies:
     • Precentral gyrus
     • Inferior parts of the postcentral gyrus

6. Postcentral (anterior parietal) artery
   • Arises from the superior division of the MCA
   • Runs in the interparietal sulcus.
   • Supplies:
     • Superior part of the postcentral gyrus,
     • Anterior part of the inferior parietal lobule
     • Anteroinferior part of the superior parietal lobule

7. Posterior parietal artery
   • Arises from the superior division of the MCA
   • Courses near the intraparietal sulcus.
   • Supplies:
     • Posterior part of the superior parietal lobule
     • Posterior part of the inferior parietal lobule
     • Supramarginal gyrus

8. Angular artery
   • Arises from the inferior division of the MCA
   • Passes over the anterior transverse temporal gyrus and usually divides into two branches.
   • Supplies:
     • Angular gyrus
     • Supramarginal gyrus
     • Posterior superior temporal gyrus
     • Parietooccipital arcus

9. Anterior temporal artery
   • Arises from the inferior division of the MCA
   • Usually arises from M1 or an early M2 branch
   • Supplies:
     • Temporal pole
     • Anterior portions of superior and middle temporal gyri

10. Temporopolar artery
    • Arises from the inferior division of the MCA
    • Usually arises from M1, the anterior temporal artery or an early M2 branch
    • Supplies the same areas as the anterior temporal artery:
      • Temporal pole
      • Anterior portions of superior and middle temporal gyri

11. Middle temporal artery
    • Arises from the inferior division of the MCA
    • Extends from the Sylvian fissure opposite to the inferior frontal gyrus.
    • Supplies:
      • Superior and middle portions of the middle temporal lobe

12. Posterior temporal artery
    • Arises from the inferior division of the MCA
    • Extends away from the operculum and turns first inferiorly then posteriorly into the superior temporal sulcus, then to the middle temporal sulcus.
    • Supplies:
      • Posterior portion of the temporal lobe
      • Multiple perforating branches to the insula

13. Temporooccipital artery
    • Arises from the inferior division of the MCA
    • The longest cortical artery. Runs parallel to the superior temporal sulcus.
    • Supplies:
      • Superior and inferior occipital gyri

Anatomic variants:

• Early MCA bifurcation (≤ 1cm of origin)
• Hypoplasia, aplasia (rare)
• MCA duplication: additional branch from ICA, courses parallel to main M1
• Accessory MCA: arises from ACA
• Fenestrated MCA (rare): division of the vessel into two separate parallel channels which rejoin distally