Paraclinoid internal carotid artery aneurysm with delayed stent occlusion after deployment of a flow diverter stent involving the orifice of the anterior cerebral artery: illustrative case.

backgroundIn-stent thrombotic occlusion is a serious ischemic complication that can also result in ischemia in the distal perfusion territory and the territory of side branches for the artery in which the flow diverter (FD) stent is deployed. OBSERVATIONS: A 49-year-old female with a large paraclinoid internal carotid artery (ICA) aneurysm was treated with an FD involving the orifice of the anterior cerebral artery (ACA). The antiplatelet dose was reduced because of an increased clopidogrel response postintervention. The patient developed aphasia 2 months later. Emergency magnetic resonance imaging and digital subtraction angiography of the brain indicated FD stent occlusion and a small infarct in the distal vascular territory of the ipsilateral ICA, but the anterior choroidal artery (AChoA) territory was preserved by collateral flow. Emergency superficial temporal artery to middle cerebral artery anastomosis was performed, and she was discharged without neurological deficit 2 weeks after the second operation. LESSONS: In-stent occlusion after FD deployment involving the orifice of the ACA can cause severe cerebral ischemia that requires an adequate antiplatelet effect and careful follow-up. The AChoA territory can be preserved by collateral blood flow even in cases of in-stent occlusion.