A Concealed Intracranial Aneurysm Detected after Recanalization of an Occluded Vessel: A Case Report and Literature Review

Background: Based on the results of several randomized controlled trials, acute endovascular thrombectomy is strongly recommended for patients with acute ischemic stroke due to large artery occlusion (LAO). The incidence of an intracranial aneurysm has been reported to be approximately 5% in the general population. Therefore, the possibility of the coincidence of LAO and an intracranial aneurysm at the distal part of an occluded vessel should be considered. Summary: A 74-year-old female patient presented with the sudden onset of consciousness disturbance and left-sided weakness. Neuroimages demonstrated an acute infarction due to right middle cerebral artery occlusion. The occlusion was successfully treated, and an aneurysm was incidentally detected at the occluded artery. We reviewed the literature and identified 11 cases in 8 reports, which were similar to our case. Among the 11 cases, aneurysms ruptured during endovascular therapy in 2 cases. In the present report, we discussed the prediction of concealed aneurysms and avoidance of their rupture during endovascular intervention. Key Message: The presence of an aneurysm concealed behind an embolus should be carefully assessed on preoperative and intraoperative neuroimages. The important findings for suspecting such an aneurysm are a hyperdense nodular sign on preoperative computed tomography and unusual motion of the microwire during the endovascular intervention. Even if there is no finding indicative of an aneurysm, the catheter and thrombectomy devices should be more carefully advanced than usual, especially at the common sites of aneurysms, and the devices should be appropriately chosen.