The insular part (M2 segment) of the middle cerebral artery extends anteriorly on the insula, this segment in known as the insular segment. It is also known as the Sylvian segment when the opercular segments are included. The MCA branches may bifurcate or sometimes trifurcate into trunks in this segment which then extend into branches that terminate towards the cortex. When they bifurcate, they are denominated in the Terminologia anatomica as:
The M2 segment is described by Gibo et al (Microsurgical anatomy of the middle cerebral artery - GiboH et al. - J Neurosurg. 1981 Feb;54(2):151-69.). as :
The M2 segment included the trunks that lay on and supplied the insula. It began at the genu of the MCA where the trunks of the MCA passed over the limen insulae and terminated at the circular sulcus of the insula. The greatest branching of the MCA occurred at the anterior part of the insula, distal to the genu. The branches passing to the anterior cortical areas had a shorter path across the insula than those reaching the posterior cortical areas: the branches to the anterior frontal and anterior temporal areas crossed only the anterior part of the insula, but the branches supplying the posterior cortical areas coursed in a nearly parallel but diverging path across the length of the insula. The frontal branches coursed over the short gyri only be- fore leaving the insular surface, whereas a branch supplying the posterior parietal or angular region passed across the short gyri, the central sulcus, and the long gyri of the insula before leaving the insular surface.