A Case of Subacute Severe In-stent Thrombosis Following Flow Diverter Stent Implantation for an Unruptured Medium-sized Internal Carotid Artery Aneurysm

Abstract

A 52-year-old man presented with an unruptured medium-sized left internal carotid artery (ICA) aneurysm approximately 5 mm in diameter. Implantation of a flow diverter (FD) with an adjunctive coil was planned. Antiplatelet therapy using aspirin and clopidogrel was administered two weeks preoperatively. The patient was suspected to be nonresponsive to clopidogrel based on a platelet aggregation test. Loading and maintenance doses of prasugrel were thus administered in place of clopidogrel. A pipeline flex with shield technology was successfully implanted, and stent wall apposition was good. Postoperatively, an anticoagulant was administered via continuous intravenous infusion for three days. While brain magnetic resonance imaging (MRI) and angiography (MRA) showed positive FD results, the patient developed a sudden-onset disturbance of consciousness, aphasia, and right hemiparesis on postoperative day 4. Brain MRI and MRA revealed an acute left cerebral infarction due to left ICA occlusion. An emergency mechanical thrombectomy for in-stent thrombosis was performed, after which the patient was transferred to a rehabilitation hospital with a modified Rankin scale score of 3. Relationships between parent vessel, aneurysm, and blood flow dynamics should be considered when deciding to perform FD alone or with adjunctive coil embolization for unruptured medium-sized intracranial aneurysms. FD with adjunctive coil embolization for aneurysms of the lesser curvature of the ICA requires particular caution due to the possibility of inducing in-stent thrombosis. Treatment with FD alone is thus recommended. An alternative option is to finish the initial treatment by coil embolization alone and perform FD placement during retreatment.