Asymmetrical Pseudotetrafurcation of the Middle Cerebral Artery: Proposal for a Novel Classification Type

The middle cerebral artery (MCA) shows significant morphological variability in its branching pattern. While bifurcation is the most common configuration, several other branching variants have been described. In this report, the authors present a new morphological variant—called asymmetrical pseudotetrafurcation—discovered during magnetic resonance angiography (MRA) in a 25-year-old woman. Imaging revealed an initial bifurcation of the MCA trunk, followed by trifurcation of one of the main branches at a distance of 1.55 mm from the primary bifurcation point, resulting in a 4-branch pattern. Unlike previously reported cases of symmetrical pseudotetrafurcation, where both branches undergo bifurcation, this asymmetrical variant involves secondary branching in only one limb, leading to spatial asymmetry. The frequency and clinical significance of this anatomical pattern are not yet fully understood. However, recognizing such MCA branching variants is essential for accurate cerebrovascular imaging interpretation and can greatly influence the planning and performance of neurosurgical or endovascular procedures.