Middle cerebral artery fenestration with a contralateral early branching investigated through magnetic resonance angiography: an embryological view on an incidental finding.

Purpose: Middle cerebral artery (MCA) anomalies are a small group of congenital variants, including fenestration, duplication and Twig-like MCA. Some other variants, i.e. in the branching pattern, have been described independently from the previous ones, but their association might raise an embryological reasoning.

Methods: We are presenting an incidental finding in a patient undergoing brain Magnetic Resonance Imaging (MRI) and Angiography (MRA) for episodic headache, i.e. right MCA fenestration and left MCA very early branching. The patient was investigated only by MRA, being the finding incidental and non-pathological. Among the intracranial arteries, MCA has a lower rate of fenestrations and several embryological hypotheses have been proposed, different from the presumed mechanisms underlying vertebral and basilar artery fenestrations. Both fenestration and early branching in MCA in our case might resemble to a partial MCA duplication with proximal and distal fusion in the first and only a proximal fusion in the second one. The pattern of distribution of the early branches in the left MCA territory may support this view, together with the lenticulostriate perforating arteries origin.

Conclusions: The association of several MCA anomalies, as fenestration and early branching, might have a common genesis within the same embryological period.