Ultrasonographic assessment of bypass capacity after revascularization surgery in moyamoya disease: a systematic review and single-arm meta-analysis.

PURPOSE: Moyamoya disease (MMD) is a chronic cerebrovascular disorder characterized by progressive arterial stenosis and fragile collateral formation, elevating stroke risk. Revascularization is the standard treatment, yet up to 27% of patients experience ischemic events within a year due to bypass insufficiency. While digital subtraction angiography (DSA) remains the gold standard for assessing bypass function, it is invasive and time-consuming. This study evaluates ultrasonography (US) as a noninvasive, cost-effective tool to assess bypass capacity post-revascularization in MMD.

METHODS

A systematic search was conducted following PRISMA guidelines. PubMed, Web of Science, and Scopus were searched for studies reporting US parameters with control imaging confirming bypass capacity. Study quality was assessed using the Newcastle-Ottawa Scale. Mean difference (MD) values were calculated using random-effects models. High bypass capacity was defined as good patency or favorable collateral development.

RESULTS

Eight cohort studies comprising 264 MMD patients and 301 operated hemispheres were included, with 180 demonstrating high bypass capacity. Within two weeks post-surgery, increased superficial temporal artery (STA) peak systolic velocity (PSV, MD = 28.26, p < 0.0001), mean flow velocity (MFV, MD = 22.97, p = 0.03), end-diastolic velocity (EDV, MD = 33.45, p < 0.0001), and decreased resistance index (RI, MD = -0.09, p = 0.006) were predictive. External carotid artery (ECA) EDV (MD = 13.92, p = 0.04) was also significant. At 3-6 months, elevated EDV in both STA (MD = 8.13, p = 0.006) and ECA (MD = 8.71, p = 0.0002) remained predictive. In the indirect subgroup, lower anterior cerebral artery (ACA) MFV within 0-3 months predicted favorable outcomes (MD = -64.98, p = 0.001).

CONCLUSIONS

Changes in STA and ECA US parameters measured following revascularization surgery predict high bypass capacity. Decreased ACA MFV suggests effective revascularization after indirect surgery. Ultrasound modality offers a valuable, noninvasive tool for postoperative assessment in MMD.