Supplementary Material for: Middle meningeal artery collateralization patterns and influencing factors in paediatric moyamoya

Introduction: The middle meningeal artery (MMArt) is considered to be an important collateral in Moyamoya angiopathy (MMA), however, an in-depth analysis of the underlying mechanisms directing this collateral formation is missing. The aim of this study was to analyze patterns of activation of MMArt in paediatric patients along with identifying factors influencing these collateral pathways.
Methods: Retrospective clinical and angiographic data of a paediatric moyamoya cohort managed at a single center was analyzed. Angiographic staging, MMArt activation and collateral supply via posterior cerebral artery (PCA) was evaluated on cerebral angiograms. Stroke burden was evaluated using cerebral MRI. Associations with angiographic staging, stroke burden and PCA collateral supply were determined.
Results: MMArt activation was observed in 49% of patients (n = 101). MMArt anterior division was activated more frequently (31% of all hemispheres). MMArt formed collaterals mostly to the frontal brain. Higher odds of activation of MMArt were observed in advanced anterior angiographic stages (stages 4-5) (OR 4.22, p < 0.001), higher posterior angiographic stages (stages 1-2) (OR 5.75, p < 0.001), longer duration of disease (OR 1.33, p = 0.014) and in cases showing collateral supply from the PCA (OR 3.39, p < 0.003). Age at symptom onset, Stroke burden and type of angiopathy (Moyamoya syndrome/disease) were not associated with MMArt activation.
Conclusions: The middle meningeal artery (MMArt) serves as a crucial collateral in paediatric moyamoya, particularly to the frontal lobes. Increased MMArt activation is seen in advanced angiopathy with prolonged disease duration and PCA-derived collaterals. Stroke burden and angiopathy subtype do not appear to influence MMArt activation.