Associations between middle cerebral artery tortuosity, aneurysm wall enhancement, and hemodynamics assessed by four-dimensional-flow and high-resolution magnetic resonance imaging.

PURPOSE: Parent artery geometry may be associated with the imaging phenotype of intracranial aneurysm. This study aimed to compare ipsilateral and contralateral M1 morphology in patients with unilateral middle cerebral artery (MCA) aneurysms and to explore the associations between parent artery geometry, aneurysm wall enhancement (AWE), and hemodynamic features. METHODS: For this retrospective study, patients with unilateral MCA bifurcation aneurysms from our maintained database were included. All patients underwent four-dimensional (4D)-flow and high-resolution (HR) magnetic resonance imaging (MRI). Parent artery morphology was quantified on standardized bilateral M1 segments, including relative length (RLength) as a tortuosity parameter, calculated as the straight-line distance between centerline endpoints divided by centerline length, and maximum radius (Radiusmax) as a dimensional parameter. Inter-side differences were assessed using paired statistical tests, and exploratory Spearman correlation analyses were performed between ipsilateral parent artery parameters and aneurysm imaging characteristics. The Benjamini-Hochberg false discovery rate method was used to adjust for multiple comparisons in the exploratory correlation analyses. RESULTS: Twenty-three patients (aged 57 [53.50-64.00]; 26.1% male) were included. The ipsilateral M1 segment showed lower RLength than the contralateral side (0.95 [0.85-0.99] vs. 0.97 [0.94-0.99]; P = 0.035). In exploratory association analyses, higher RLength showed nominal positive correlations with average aneurysm-to-pituitary stalk contrast ratio (CRstalk-avg; r = 0.539, raw P = 0.008, FDR-adjusted q = 0.403) and maximal inflow velocity (Vmax; r = 0.444, raw P = 0.034, FDR-adjusted q = 0.560), whereas Radiusmax showed a nominal negative correlation with time-averaged wall shear stress (TAWSS; r = - 0.511, raw P = 0.013, FDR-adjusted q = 0.403). CONCLUSION: In MCA bifurcation aneurysms, M1 geometry differed between the aneurysm ipsilateral and contralateral sides. Ipsilateral parent artery geometry showed preliminary exploratory relationships with aneurysm wall enhancement and hemodynamic features, which warrant further validation in larger independent cohorts.