[Trifurcations of the middle cerebral arteries]

The furcation types of 100 human middle cerebral arteries (MCA) were investigated. Considering the physiological flow characteristics in furcations, a distinct definition for a bifurcation and a trifurcation was found. The common ramification type of the human MCA is the bifurcation. Trifurcations are very rare and we found them only in the proximal parts of the MCA. In 7 of the 100 cases, a trifurcation was found at the main division of the MCA, in 3 cases a secondary trunk trifurcated. Quadro- and pentafurcations according to the hydrodynamic definitions were not observed at all. Only in 1 case did the internal carotid artery trifurcate into the anterior cerebral artery, a superior trunk and an inferior trunk of the MCA.