The middle cerebral artery (MCA) arises in the embryogenesis as the latest branch from the cranial division of the ICA and develops to the largest artery supplying a large part of the cerebral hemispheres and basal ganglia. The development of the MCA correlates with the great extension of the cortical mantle in the mammal (Kier 1974). As visible in Drawings 5.1 and 5.2 the artery can be divided into four segments: M1 segment, running horizontally in the Sylvian fissure M2 segment, running vertically on the surface of the insula M3 segment, running laterally and exiting the insular cistern M4 segment, which comprises the distal cortical branches