Contralateral Disease Progression in European Moyamoya Patients: Risk Patterns Across Angiographic Subgroups and Association with Vessel Wall Contrast Enhancement

Background/Objectives: Contralateral disease progression (CDP) in Moyamoya disease (MMD) is a clinically relevant phenomenon, yet difficult to predict. We investigated the association between vessel wall contrast enhancement (VW-CE) and CDP in a European cohort of adult MMD patients with initially unilateral hemodynamic impairment treated with unilateral revascularization. Methods: In this retrospective single-center study, patients with an indication for only unilateral revascularization (based on BOLD fMRI or H215O-PET) were stratified into three subgroups according to contralateral Suzuki grade (0, 1, or ≥2). CDP was defined as secondary contralateral disease progression on imaging with hemodynamic worsening requiring contralateral revascularization during follow-up. Results: Of 158 screened patients, 38 with adequate follow-up were included. CDP occurred in 31.6% (n = 12; 13.6%, 71.4%, and 44.4% in groups 1–3; mean follow-up 2.71 years). In time-to-event analysis, CDP occurred earlier in groups 2 and 3 than in group 1, without reaching significance (log-rank p = 0.078). Patients who later developed CDP more often showed preoperative VW-CE in either hemisphere (90.0% vs. 43.5%, p = 0.021), with consistent but non-significant trends for each hemisphere separately. De novo contralateral VW-CE occurred exclusively in CDP(+) patients (n = 4); contralateral VW-CE overall was significantly more common in CDP(+) than stable patients at the time of CDP (70% vs. 4.3%, p < 0.001). Conclusions: In this exploratory study, contralateral angiographic involvement and preoperative VW-CE were associated with CDP in unilaterally treated MMD patients. De novo contralateral VW-CE may represent a candidate imaging marker of active CDP. Larger multicenter studies are needed to confirm these hypothesis-generating findings.