Background and purpose Little is known about the safety of long-term anticoagulation in patients with unruptured saccular intracranial aneurysms, although case reports of anticoagulation in patients with fusiform and saccular aneurysms have been published. The goal of this study was to estimate the rate of subarachnoid hemorrhage (SAH) due to aneurysm rupture in patients with intracranial saccular aneurysms receiving therapeutic doses of anticoagulation.

Methods This was a retrospective case series of patients with intradural aneurysms receiving therapeutic doses of anticoagulation (defined as a dose that achieves a target INR >2.0 or the equivalent dose of another anticoagulant). The primary outcome was SAH due to aneurysm rupture while receiving anticoagulation treatment. The rate of SAH due to aneurysm rupture was calculated among patients with aneurysms documented on imaging.

Results 42 patients with 48 intradural aneurysms on anticoagulation were identified. Their mean age was 67 years (range 40–83) and 28 (67%) were women. The mean aneurysm size was 5.1±3.6 mm and 40 (83%) aneurysms were in the anterior circulation. The mean±SD follow-up was 495±749 days per patient. Twelve patients had their aneurysms coiled, clipped or surgically wrapped before the period of anticoagulation. Three patients had clipping or coiling of their aneurysms during the period of anticoagulation. Six patients had a history of aneurysm rupture prior to anticoagulation, of which two were treated by coiling and four by clipping. Among the 48 aneurysms, 32 were never coiled or clipped prior to anticoagulation. No anticoagulated patients with known aneurysms developed SAH during 57 patient-years of follow-up. The patients with untreated aneurysms had 31 patient-years of follow-up and those who underwent clipping, coiling or surgical wrapping of their aneurysms had 26 patient-years of follow-up while receiving anticoagulation (for a combined total of 57 years of follow up).

Conclusions The risk of aneurysm rupture is not increased in patients receiving systemic anticoagulation. However, these results should be interpreted with caution given the small sample size in this study and the need for a prospective study to confirm these findings.