Hemodynamic differences between intracranial and extracranial dissecting aneurysms: An analysis of shear forces and their clinical implications.

Intracranial carotid dissecting aneurysms (DA) are often treated emergently upon diagnosis. In contrast, extracranial DA are generally considered less likely to rupture and are commonly managed conservatively. Despite these clinical differences, limited data exists on the hemodynamic differences that might explain their divergent clinical behaviors. Retrospective analysis of intracranial and extracranial DA treated between 2011 to 2023. DA were reconstructed from computerized angiographic images using 3D Slicer software. Computational fluid dynamics (CFD) simulations were performed using ANSYS® Fluent package. Hemodynamic parameters calculated included time averaged wall shear stress (TAWSS), high shear areas (HSA), low shear areas (LSA), time averaged wall shear stress ratio (TAWSR), oscillatory shear index (OSI), and relative residence time (RRT). We compared these variables between extracranial and intracranial lesions using Mann-Whitney U and t-tests. Nineteen DA (10 extracranial, 9 intracranial) from 16 patients (age 48-82; 9 male) were analyzed. The average volume and area of the lesions evaluated were 187 mm3 and 158.6 mm2. Two of the intracranial DA were identified in the setting of subarachnoid hemorrhage. Extracranial DA showed significantly greater volume (234.6 vs. 83.0 mm3; p = 0.02) and area (210.9 vs. 59.4 mm2; p = 0.03). Intracranial DA demonstrated nonsignificant trends toward lower TAWSS at the aneurysm (1.04 vs. 1.53 Pa; p = 0.62), lower TAWSSR (0.49 vs. 0.7; p = 0.19), greater LSA (4.2% vs. 2.7%; p = 0.28) and higher RRT (2.16 vs. 1.36 m2/N; p = 0.29). This study identified hemodynamic trends in intracranial DA (higher LSA and higher vessel wall TAWSS in relation to the DA) that may account for the differential clinical behavior and increased risk of rupture.