Article Text
Abstract
Introduction In about 80% of individuals, the horizontal M1 middle cerebral artery (MCA) bifurcates at the level of the insula into a vertical M2 superior and M2 inferior segment with one of them being dominant. However, the variability of M2 MCA segments with respect to caliber and territory supplied creates a debate on how to classify M2 MCA occlusions. A protocolized approach could harmonize thrombectomy trial inclusion criteria and facilitate understanding of thrombectomy treatment effects in M2 MCA occlusion stroke. Here, we seek to evaluate procedural and outcome parameters among patients who underwent MT for emergent occlusion of the M1, M2 superior or M2 inferior MCA with focus on dominance assessment of the M2 segments.
Materials and Methods Large vessel occlusion strokes undergoing MT between 02/2016–08/2022 were reviewed (n=784). M1 (n=431) and M2 MCA (n=118) occlusions were assessed. Among M2 MCA occlusions, prototypical MCA bifurcation anatomy cases were classified as superior and inferior as well as dominant and non-dominant branches (n=99). Dominance of the M2 segment was allocated to either segment based on temporal lobe supply, proportional contribution to MCA territory perfusion of at least 50%, and proximal M2 segment luminal caliber. Procedural and outcome data was compared between M1, M2 superior, and M2 inferior MCA occlusions.
Results Compared to patients with M1 MCA occlusions (n=431), M2 MCA occlusions (n=99) were older (p=0.024), had lower baseline NIHSS (p=< 0.001), and higher CT-ASPECTS (p=0.021). A stent-retriever was used significantly more frequently in the M2 MCA occlusion group compared to the M1 MCA occlusion group (p=0.005), while the median number of passes was similar (p=0.446). The intracranial hemorrhage, parenchymal hematoma type 2, and subarachnoid hemorrhage rates were similar between groups (p=0.180, p=0.783, p=0.191, respectively).Demographics and periprocedural criteria of MCA M2 superior (n=56) and M2 inferior (n=43) division occlusions were comparable. Among M2 inferior cases, the occluded branch was dominant in 41/43 (95.3%), but only in 37/56 (66.1%) among M2 superior cases (p<0.001). The 90-day favorable functional outcome (mRS 0–2) and mortality (mRS 6) rates were 60.0% and 8.9% in the M2 superior, 42.9% and 32.6% in the M2 inferior, and 44.1% and 26.0% in the M1 group (n=431), respectively. Compared to M2 superior, M2 inferior favorable outcome (mRS 0–2) rates were lower (p=0.094) and mortality (mRS 6) rates were higher (p=0.003). M2 inferior outcome rates resembled those of M1 (p=0.750 and p=0.355, respectively).
Conclusion In the setting of prototypical MCA bifurcation anatomy, dominant M2 inferior division occlusions had outcome rates like M1 occlusions after mechanical thrombectomy. In contrast, M2 superior division occlusions had significantly lower mortality rates and a trend towards better favorable functional outcomes.
Disclosures P. Koul: None. M. Collins: None. T. Bielinski: None. A. Noto: None. C. Schirmer: None. P. Hendrix: None.