Delayed Posttreatment Residual Flow into Aneurysm After Flow Diverter Placement.

Background: Inflow into an aneurysm sac immediately following flow diverter (FD) treatment is an assumed cause of delayed aneurysmal rupture. The significance of delayed posttreatment residual flow occurring months after FD treatment is unknown.

Case Description: A 76-year-old woman with a large intracranial aneurysm measuring 23.0 × 18.1 mm in the cavernous segment of the right internal carotid artery was treated with placement of a single FD (Pipeline Embolization Device, Covidien, Irvine, California, USA). Postprocedure digital subtraction angiography (DSA) demonstrated flow stagnation inside the aneurysm dome. The patient was discharged 9 days post procedure without new neurologic deficits. A 6-month follow-up DSA demonstrated delayed posttreatment residual flow into the aneurysm sac. Although she was scheduled for additional FD placement because of concern for aneurysmal rupture, the operation was not conducted due to an interim motor vehicle accident. Oral treatment with aspirin (100 mg/day) and clopidogrel (75 mg/day) was continued during her recovery. DSA performed 12 months post procedure showed that the aneurysm had completely thrombosed.

Conclusions: Our findings suggest that delayed post-treatment residual flow into an aneurysm may form part of the normal clinical course post FD placement and may not preclude eventual thrombosis of the aneurysm. Larger studies are needed to determine whether more frequent follow-up DSAs after FD placement are necessary and whether all patients exhibiting delayed post-treatment residual flow into an aneurysm require additional FD placement or if watchful waiting is a more suitable course.