Recurrent Embolic Stroke Caused by a Thrombosed Common Carotid Artery Aneurysm: An Uncommon and Initially Indeterminate Source of Embolism.

Recurrent ischemic stroke with no clearly identified embolic source poses a significant diagnostic challenge. We report the case of a 73-year-old woman who experienced four episodes of cerebral infarction, all localized to the right middle cerebral artery territory. According to medical records from the referring hospital, the first three strokes occurred over three years. They were diagnosed as having an embolic stroke of undetermined source after extensive evaluation failed to identify a definitive cause. Although carotid ultrasonography and magnetic resonance angiography had revealed a right common carotid artery aneurysm during earlier evaluations, the absence of thrombus led clinicians to exclude it as an embolic source. At the time of the fourth stroke, follow-up carotid ultrasound demonstrated turbulent flow and bright, mobile intraluminal structures within the aneurysm, strongly suggesting thrombus formation. The patient subsequently underwent successful endovascular treatment with stent placement and coil embolization. No recurrence of stroke has been observed during the five-year follow-up. This case highlights that extracranial carotid artery aneurysms, although rare, should be considered as potential embolic sources, particularly when intra-aneurysmal thrombus is suspected. Endovascular intervention may be an effective strategy to prevent recurrent embolic stroke in such patients.