Last year at this meeting we demonstrated that high-resolution (HR) CFD simulations could detect a highly transient response to steady inflow conditions in 5 of 12 MCA aneurysm cases [1]. We also showed preliminary results suggesting that normal resolution (NR) simulations, representative of those from the clinical literature (e.g, [2,3]), might be misleading about the nature of aneurysm flow patterns and wall shear stress (WSS), and hence derived predictors of rupture risk. We now test this hypothesis in a controlled manner, by comparing NR vs. HR simulations of physiologically pulsatile flow in the 12 MCA aneurysm cases from [1].