Timing treatment of a giant intracranial aneurysm by the use of magnetic resonance imaging for the determination of intraluminal clot stability.

A 44-year-old man presented with a giant intracranial carotid artery aneurysm. Magnetic resonance (MR) images demonstrated a large amount of fresh intraluminal thrombus in the aneurysm. During test occlusion of the internal carotid artery using an endovascular balloon positioned in the cervical portion of the internal carotid, the patient sustained an apparent embolic episode. The patient was followed for several weeks with serial MR imaging until the thrombus had lysed. Repeat test occlusion followed by permanent carotid occlusion was uneventful. Serial MR evaluations of intraluminal thrombus in large aneurysms might help to determine an optimal time for institution of intervention.