Delayed thrombus propagation after parent artery clipping for giant fusiform aneurysms of the circle of Willis

BACKGROUND Obliteration of a giant fusiform aneurysm without significant th erapeutic morbidity is extremely difficult. Ischemic complications have bee n often reported. METHODS Two patients with giant fusiform aneurysms of the circle of Willis are presented. Both patients underwent proximal parent artery clipping afte r a bypass procedure. Balloon occlusion tests confirmed both patients' abil ity to tolerate now reduction after proximal clipping. RESULTS Although both patients awoke from anesthesia without neurologic def icit, they developed contralateral hemiparesis several hours after the oper ation as a result of a small infarct in the basal ganglia. These ischemic e vents might be attributed to the delayed thrombosis involving the orifice o f the distal perforating arteries. CONCLUSIONS In the treatment for giant fusiform aneurysms of the circle of Willis, special attention should be paid not only to flow reduction, but al so to delayed thrombus propagation that may not be predicted by preoperativ e balloon occlusion testing. (C) 1999 by Elsevier Science Inc.