Correlation Between Laminar Wall Shear Stress and Growth of Unruptured Cerebral Aneurysms: In Vivo Assessment

Cerebral aneurysm growth is significantly associated with aneurysm rupture, but risk factors for aneurysm growth are not well characterized. It is believed that altered intracranial hemodynamics may contribute to the pathophysiology of aneurysm growth, but these mechanisms are not fully understood.

Here, we assess the correlation between growth of unruptured cerebral aneurysms over time and average laminar shear stress on the wall of the parent vessel proximal to the aneurysm.

Patients with unruptured, untreated cerebral aneurysms followed over time at our institution between 2005 and 2017 were retrospectively reviewed. Patients were included if at least 1 quantitative magnetic resonance angiography study was performed at baseline and follow-up. The nonparametric Wilcoxon-Mann-Whitney test was used to compare mean parent vessel-laminar wall shear stress (PV-LWSS) proximal to the aneurysm in growing versus stable aneurysms. Change in PV-LWSS over time was evaluated using the 1-way repeated measures analysis of variance test.

Thirty-three patients with 45 total aneurysms were included (63% female, mean age 60 years). Four patients presented with aneurysm growth over time. Unstable aneurysms had significantly higher PV-LWSS compared with stable aneurysms at the time of first diagnosis (29.3 vs. 13.1 dynes/cm², P = 0.02) and at 1-year follow-up (25.8 vs. 12.3 dynes/cm², P = 0.05).

The subset of unruptured cerebral aneurysms that demonstrate growth over time has a significantly higher mean PV-LWSS than stable aneurysms, as measured by quantitative magnetic resonance angiography. This information at the time of diagnosis may help predict future aneurysm growth, stratify rupture risk, and identify those aneurysms that should undergo prophylactic treatment.