Revascularization surgery for the symptomatic hemisphere with hemodynamic impairment is effective for Moyamoya vasculopathy patients. However, careful patient selection is crucial and ideally supported by advanced quantitative hemodynamic imaging. Recently, blood oxygenation level-dependent cerebrovascular reactivity (BOLD-CVR) and quantitative magnetic resonance angiography with non-invasive optimal vessel analysis (qMRA-NOVA) have gained prominence in assessing these patients. This study aims to present the results of BOLD-CVR and qMRA-NOVA imaging along with the changes in cerebral hemodynamics and flow status following flow augmentation with superficial temporal artery–middle cerebral artery (STA-MCA) bypass in our Moyamoya vasculopathy patient cohort. Symptomatic patients with Moyamoya vasculopathy treated at the Clinical Neuroscience Center of the University Hospital Zurich who underwent hemodynamic and flow imaging (BOLD-CVR and qMRA-NOVA) before and after bypass were included in the analysis. Reduced hemispheric volume flow rates, as well as impaired BOLD-CVR, were measured in all 12 patients with Moyamoya vasculopathy before STA-MCA bypass surgery. Following the surgical procedure, post-operative BOLD-CVR demonstrated a non-significant increase in BOLD-CVR values within the revascularized, symptomatic middle cerebral artery territory and cerebral hemisphere. The results of the statistical tests should be viewed as indicative due to the small sample size. Additionally, post-operative qMRA-NOVA revealed a significant improvement in the hemispheric volume flow rate of the affected hemisphere due to the additional bypass flow rate. Our findings affirm the presence of hemodynamic and flow impairments in the symptomatic hemisphere of the Moyamoya vasculopathy patients. Bypass surgery proves effective in improving both BOLD-CVR impairment and the hemispheric volume flow rate in our patient cohort.

Background/Objectives: Haemodynamic changes following ischaemic large-vessel occlusion (LVO) stroke might affect clinical outcome, including after endovascular recanalization. Using non-invasive quantitative MRA (qMRA), we report for the first time serial intracranial flow rate measurements following LVO and investigate flow rate changes, collateral pathway development, and their possible clinical significance. Methods: We report data from the prospective IMPreST study (Interplay of Microcirculation and Plasticity after Ischemic Stroke, registered at clinicaltrials.gov, no. NCT04035746). Patients with first-ever unilateral internal carotid artery (ICA) and/or M1/2 middle cerebral artery (MCA) occlusions were included. After being evaluated for gold-standard treatment, including endovascular thrombectomy, patients underwent early (<3 days) and late subacute (7 ± 3 days) qMRA flow measurements of the M1-MCA, A2-ACA (anterior cerebral artery), and P2-PCA (posterior cerebral artery) segments bilaterally. Results: Among 31 patients enrolled, 23 patients (17 recanalized, 6 non-recanalized) received both qMRA sessions. M1 volume flow rate (VFR) ratios (ischaemic/non-ischaemic hemisphere) in recanalized patients were symmetric (0.98–1.01) over time, while in non-recanalized patients M1 VFR ratios remained lower (0.74–0.77). P2 VFR ratios increased over time and were negatively correlated with M1 VFR ratios in late measurements (p = 0.016), possibly reflecting subacute activation of leptomeningeal collaterals via P2-PCA. In recanalized patients, lower M1 VFR ratios at 7 ± 3 days were significantly associated with a higher NIHSS at discharge after adjusting for infarct size, age, and NIHSS at admission (p = 0.02). Total hemispheric flow significantly decreased by up to 9% between early and late measurements in both the ischaemic and non-ischaemic hemispheres (p = 0.005). Conclusions: qMRA may help to understand flow status and collateral pathway activation after LVO stroke. Past the acute phase, low arterial flow to the affected region is associated with poorer neurological status, including after successful recanalization.

Background/Objectives: Bilateral steno-occlusive disease of the internal carotid artery (ICA) carries an increased stroke risk with associated high morbidity and mortality. Management of these patients is often complex. In this study, we evaluate the value of non-invasive optimal vessel analysis quantitative magnetic resonance angiography (NOVA-qMRA) for studying flow and collateral patterns in patients with bilateral carotid steno-occlusive disease. Methods: Patients with bilateral ICA-stenosis ≥ 50% who received NOVA-qMRA were included in this study. The volume flow rates (VFRs) of the A2-segment of the anterior cerebral artery (A2-ACA), M1-segment of the middle cerebral artery (M1-MCA), and P2-segment of the posterior cerebral artery (P2-PCA) were analyzed. Demographic, clinical, and treatment data were collected. Results: Twenty-two patients (mean age ± SD: 68 ± 10 years) were included. Nineteen patients (86%) were symptomatic. Thirteen patients (59%) were revascularized; among them, M1-VFR was significantly lower (p-value = 0.01) on the side selected for revascularization (88 mL/min ± 53) compared to the contralateral one (130 mL/min ± 56). P2-VFR was significantly higher (p-value = 0.04) in the treated subgroup (108 mL/min ± 41) than in the non-treated one (83 mL/min ± 34). Conclusions: The present study supports the use of NOVA-qMRA to study flow and collateral patterns in patients with bilateral steno-occlusive carotid disease, especially M1- and P2-VFR. This information may be helpful for decision-making and to tailor revascularization treatment.