Hemorrhagic events associated with unfused or twig-like configuration of the Middle cerebral artery: A rare vascular anomaly with clinical relevance

Abstract

Introduction: Twig-like middle cerebral artery configuration (Tw-MCA) is a rare and commonly misdiagnosed vascular anomaly characterized by a plexiform arterial network that replaces the normal M1 segment. The prevalence and clinical relevance of this anomaly is not fully established.

Material and methods: We sought to explore the prevalence of Tw-MCA in patients clinically referred to digital angiography in a single academic comprehensive endovascular center and evaluated the radiological and clinical findings among patients with hemorrhagic events.

Results: From 2011 to 2020, a total of 10,234 patients underwent a cerebral angiography at our institution. During this period, 9 (0.088%) Tw-MCAs were identified. Out of these, 5 patients (62.5%) were admitted due to an intracranial hemorrhage. Two patients had a ruptured intracranial aneurysm on the anterior communicating artery, one with multiple brain aneurysms; two patients presented an intraparenchymal hematoma (IPH) due to the presence of a periventricular anastomosis and one patient an intraventricular hemorrhage with unclear origin.

Conclusion: Tw-MCA is a very rare vascular anomaly associated with hemorrhagic events. Adequate identification of this anomaly is essential in order to avoid misdiagnosis as steno-occlusive disorders.

Keywords: MCA anomalies; Twig-Like MCA; middle cerebral artery; unfused MCA.

Figure 1.

Different stages in MCA development. Cerebral arteries in a 11 mm human embryo (a). At this stage, a plexiform arterial network arises from the distal internal carotid artery, at the lateral aspect of the telencencephalic vesicles (1), proximal to the primitive olfactory artery. At a later stage, the plexiform network progressively turns into multiple arterial twigs eventually fusing into a single arterial channel, becoming the M1 segment. A hypothetical evolutionary arrest during this process may result in the twig-like MCA phenotype in adults (b). Normal adult configuration MCA (c).

Figure 2.

Frontal DSA projection of the left ICA in early and late arterial phase (a,b). Lateral DSA projection of the left external carotid demonstrating the lack of transdural anastomosis (c). Tridimensional DSA reconstruction shows the diagnostic criteria, the white arrow shows no evidence of stenosis in the ACA or the ICA. The vascular plexus of the MCA is presented with the LSA arising from the plexus (white Asterix) and the normal configuration of the M2 and M3 segments (white head arrow) (d).

Figure 3.

Forty-eight-year-old female with a right frontal paraventricular IPH shown in non-contrast brain CT (a), frontal DSA projection of the right ICA with a Tw MCA configuration (b), oblique DSA projection with the presence of ipsilateral periventricular anastomoses (black circle) between an LSA (black arrow) and a medullary artery in the periventricular zone (c).

Figure 4.

Forty-eight-year-old female who suffered a SAH due to a right axis ruptured AcomA aneurysm with an associated bleb formation and left Tw-MCA configuration (a,b,c). The aneurysm was treated with coils, at the three-year follow-up DSA, no modifications were identified in the Tw-MCA pattern, with occlusion of the previously treated aneurysm (d).

Figure 5.

Diagnostic DSA with tridimensional reconstruction showing a periventricular anastomosis, the anterior choroidal artery (black arrow) ending in a medullary periventricular artery in the lateral ventricle (black circle), (d) in a female patient with a left temporal IPH with a homolateral Tw-MCA.