Abstract
Acute thrombosis is often observed following the rupture of an intracranial aneurysm, and optimal coil selection during endovascular coiling is challenging. A 75-year-old woman presented with a subarachnoid hemorrhage. Computed tomography angiography revealed aneurysms at the right anterior cerebral artery A2/3 junction and the right middle cerebral artery. Based on vessel wall imaging, the anterior cerebral artery aneurysm was diagnosed as the rupture site. Initial digital subtraction angiography demonstrated a 4.4 × 3.4 × 3.4 mm aneurysm with a 1.6 mm neck. Coil embolization was performed 1 day after diagnostic angiography. Preprocedural angiography revealed significant lumen shrinkage to 2.0 mm, probably due to aneurysmal thrombosis. A 4 mm framing coil was selected based on the initial digital subtraction angiography findings. Contrast extravasation occurred after coil deployment. Immediate protamine administration, blood pressure reduction, and coil embolization with smaller coils in the opacified aneurysm dome achieved hemostasis. Final angiography confirmed complete occlusion, without residual filling or distal thrombus migration. Postoperative computed tomography showed an intracerebral hematoma in the left frontal lobe, which subsequently resolved. The patient recovered without focal neurological deficits and was transferred to a rehabilitation hospital on day 18 with mild attention deficits. This case demonstrates the risk of intraprocedural rupture when coil sizing is selected based on pre-thrombosis dimensions rather than current lumen visualization in rapidly thrombosing aneurysms. When thrombosis reduces the lumen, selecting the coil size based on pre-thrombosis dimensions may increase the risk of intraoperative rupture. Coil size selection should match the currently visualized lumen.