Elena Zapata-Arriaza, MD PhD

Thirugnanachandran T, Beare R, Mitchell M, Wong C, Vuong J, Singhal S, Slater LA, Hilton J, Sinnott M, Srikanth V, et al. Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography. Stroke. 2021.

Anterior cerebral artery (ACA) stroke is less frequent when compared with middle cerebral artery (MCA) occlusion, and consequently, mechanical thrombectomies, perfusion studies, pial collateral system or clinical consequences based on the topography of the lesion are less known. With the aim of evaluating the role of the circle of Willis (CoW) and leptomeningeal anastomoses (LA) in modifying regional variation in infarct topography following occlusion of the anterior cerebral artery and its branches, Thirugnanachandran and colleagues employed voxel-based imaging in conjunction with computer model of cerebral circulation to understand the temporal and spatial evolution of the topography of ACA stroke following vessel occlusion. The experiments included occlusion of successive branches of the anterior cerebral artery while the configurations of the CoW were varied.

Among 47 included patients, the regions with the highest probabilities of infarction were the superior frontal gyrus and anterior cingulate gyrus. The regions around the posterior cingulate gyrus, paracentral lobule, precuneus and superior parietal lobule had a low probability of infarction. Following occlusions distal to the anterior communicating artery, the computer model demonstrated an increase in flow (>30%) in neighboring cortical arteries with leptomeningeal anastomoses. In contrast to the CoW generally being regarded as the primary collateral system, this study found that the adaptive response of an intact CoW was only sufficient in restoring blood flow to the vascular territory of the occluded vessel when the occlusion was proximal to the Acom. The CoW was not able to support blood flow to the cortical branches following a distal vessel occlusion. ACA stroke occurred without evidence of a larger A1 to M1 diameter ratio.

According to this study, the more distal the occlusion, the better the compensations for LA, thanks to the contribution of the MCA and the PCA. One of the areas with the highest probability of infarction after occlusion of the ACA is the anterior cingulate gyrus, which participates in motor control and seems to play a relevant role in the origin of schizophrenia. This study should make us see the relevance of ACA occlusion, especially if it is proximal, due to the poverty in leptomeningeal compensation as well as the need to improve knowledge of its functions to develop pathways to augment collateral flow in this region.