Small aneurysms as a cause of thromboembolic stroke.

OBJECTIVE AND IMPORTANCE A small percentage of patients with intracranial aneurysms present with embolic stroke distal to the site of the aneurysm. Thromboembolism typically occurs in large or giant aneurysms where reduction of flow within the aneurysm is thought to increase the possibility of clot formation. Only a few examples are available in the literature of patients with smaller aneurysms who develop embolic infarction distal to the lesion. We have experience with two such patients with an apparent common pathophysiology. CLINICAL PRESENTATION Patient 1 with a distal left middle cerebral artery infarct was found to have an 18 mm carotid artery bifurcation aneurysm (patient age 49 years). Patient 2 had a 7 mm right middle cerebral artery aneurysm with a small distal embolus (patient age 65 years). At surgery both patients were found to have atherosclerotic disease involving the aneurysm base and parent vessel. In each instance, the aneurysm was opened during temporary vessel occlusion and microendarterectomy was performed. Occlusion of one of the major arterial branches exiting the aneurysm was also present with anterior cerebral artery occlusion in the case of ICA bifurcation lesion and MCA branch occlusion in the case of the MCA aneurysm. Both patients made a good recovery following surgery. CONCLUSION In small aneurysms with atherosclerotic disease distal thromboembolism may occur. Surgical treatment with microendarterectomy is appropriate to prevent further emboli and potential for subarachnoid hemorrhage. (Fig. 5, Ref. 16.)