Perianeurysmal edema is a rare but increasingly reported complication of intracranial aneurysms. However, its pathophysiology remains unclear.

We aimed to evaluate the prevalence, risk factors, and clinical significance of perianeurysmal edema.

This prospective single-center study included patients with intracranial aneurysms who underwent endovascular treatment between January 2008 and October 2013 and a 3-Tesla MRI follow-up 3 months after treatment. Clinical, anatomic and angiographic variables were prospectively recorded and the MRI blindly reviewed. Perianeurysmal brain edema was defined as high signal intensity on FLAIR images around the aneurysm not corresponding to an arterial territory. Patients with and without perianeurysmal edema were compared using a logistic regression model to identify predictors of perianeurysmal edema.

Perianeurysmal edema occurred in 20 of 277 patients (7.2%) and 20 of 314 intracranial aneurysms (6.4%) on MRI follow-up 3 months after endovascular treatment. Five patients (25.0%) developed symptoms that could be related to the edema. Aneurysm maximal diameter (OR 1.17, 95%CI [1.04–1.32], P=.01), aneurysm in contact with parenchyma (OR 8.11, 95%CI [1.02–64.93], P=.04) and recurrent aneurysm (OR 3.34, 95%CI [1.08–10.35], P=.03) were independent predictors of perianeurysmal edema. Six out of 8 patients who had complementary injected T1-weighted images presented aneurysmal wall enhancement.

Perianeurysmal edema is not uncommon, is symptomatic in a quarter of patients and associated with a high rate of recurrence. The risk factors associated with perianeurysmal edema support the concept that its pathogenesis results from a combination of mechanisms such as mass effect, hemodynamic stress and inflammation.