Quantitative Analyisis of Preoperative Vascular Collateralization from Contralateral Hemisphere in Moyamoya Patients Undergoing Encephaloduroarteriosynangiosis (EDAS)

Introduction: While some adult patients with Moyamoya disease (MMD) demonstrate substantial collateral formation following encephaloduroarteriosynangiosis (EDAS), others experience inadequate new collateralization, leading to suboptimal clinical outcomes. Current literature presents inconsistencies regarding the factors associated with EDAS failure. This study aims to quantitatively analyze the relationship between the degree of preoperative collateral vessel formation from the contralateral circulation and the success of EDAS procedure.

Methods: We developed a method of analyzing preoperative internal carotid artery digital subtraction angiographies (DSAs) to quantify the degree of collateralization before EDAS procedures. DSA sequences were preprocessed and normalized across patients and manual masking was performed to identify Moyamoya and contralateral regions. Secondary automatic masking was performed whereby pixels were either included or excluded when compared with the gamma variate curve and the background intensity, extracting vasculature. Pixel densities for the regions were calculated by a sum over the time density curves of the valid pixels. Contralateral:Moyamoya pixel density ratios were calculated as a proxy for the degree of preoperative collateral formation. Success of EDAS was defined by the novel Orbital Grading Classification, where grades 0 and 1 are classified as a failure and grades 2 and 3 are classified as a success.

Results: Eighteen out of 56 (32.1%) revascularized hemispheres failed EDAS procedure, of which thirteen (72.2%) had preoperative contralateral collateralization. Contralateral:Moyamoya hemispheric pixel density ratios in preoperative DSAs was significantly higher in patients that failed EDAS (p < 0.05).

Conclusion : Increased formation of contralateral collateral circulation is a predictor of EDAS failure. This may be due in part to sufficient tissue perfusion from preoperative collaterals, and therefore lower drive for post-operative neovascularization. This observation may assist in optimizing patient selection for EDAS. Further investigation is required to determine whether MMD patients having contralateral hemisphere collateralization on preoperative angiography could achieve superior outcomes with alternative bypass procedures.