Gravity-driven flow for intracranial saccular aneurysm filling

Intracranial aneurysms (IAs) are life-threatening cerebrovascular malformations in which complete and durable sac closure is the primary goal of endovascular treatments, including coiling, stent-assisted coiling and flow-diverter implantation. However, standard catheter-based approaches may fail to fully occlude the sac and are limited by the need for direct access. Liquid embolic agents offer better geometric conformity, but their deployment remains constrained by similar access issues. In this study, we present a gravity-driven approach for distal filling of IAs. Through a combination of analytical modelling, in vitro experiments with idealized aneurysm models, and patient-specific computational fluid dynamics (CFD) simulations, we demonstrate that efficient filling of aneurysm cavities from relatively remote locations may be achieved using a heavier injectable fluid, while properly adjusting tilt angle and injection flow rate. A phase diagram of flow regimes highlights the interplay between gravitational, inertial and viscous forces critical to successful filling. Our findings show that slow, gravity-assisted injections minimize bypass and spillover, enabling targeted aneurysm filling even in complex geometries. CFD simulations highlight the need for patient-specific planning of such a procedure accounting for personal vascular anatomy. This strategy may provide a safer and less invasive alternative to current endovascular techniques, especially for anatomically inaccessible aneurysms.