Unfused or twig-like middle cerebral artery

The knowledge of anatomic variations of the cerebral arterial circulation may be important to decide on the safest surgical or endovascular treatment method. Variations in the middle cerebral artery (MCA) territory seems to be less frequent than the other intracranial arteries. During the embryonic stage the primitive MCA is hypothesized to be made up of arterial twigs and these twigs will generate the definitive MCA at the end of the development stage. As in our cases, an early interruption in this period will prevent the evolution of MCA normally and a plexiform arterial network will create the M1 segment of MCA which is the so-called extremely rare unfused or twig-like (Uf/Tw) MCA variation. Our aim is to define and evaluate the angiographical features of Uf/Tw MCA.

The diagnosis of Uf/Tw MCA was evaluated in a total of 4855 diagnostic cerebral catheter angiograms, retrospectively. The coexisting intracranial pathologies were also interpreted with former radiological examinations. A review of the literature is provided.

A total of six cases of Uf/Tw MCA was identified on angiograms accompanying ipsilateral internal carotid artery (ICA) occlusion and contralateral ICA supraclinoid segment aneurysm in one case, and cingulate gyrus AVM in the other. In two different cases, CT or MRI examinations revealed coexisting subarachnoid hemorrhage and misdiagnosis of forniceal AVM in one case, and temporal arachnoid cyst and parenchymal hematoma in the other.

Lack of data and knowledge about the Uf/Tw MCA variation may cause misdiagnosis and unnecessary treatment attempts.