Ischemic events associated with unruptured intracranial aneurysms: multicenter clinical study and review of the literature.

OBJECTIVE To determine the prevalence, clinical characteristics, and long-term outcomes in cases involving transient ischemic attacks (TIAs) or ischemic strokes secondary to embolization from unruptured intracranial aneurysms. METHODS We identified all available patients with intracranial aneurysms and ischemic strokes in three university-affiliated hospitals, using either International Classification of Diseases-9th Revision codes or local registries. Patients with clinically or radiologically detected cerebral infarctions distal to intracranial aneurysms, in the absence of other causes for the infarctions, were included. An aneurysmal embolic source was considered highly probable by the primary neurosurgeon/neurologist in all cases. Follow-up data for the patients were acquired through reviews of clinical visits or telephone interviews. A review of the literature was performed to identify characteristics of previously reported patients. RESULTS Ischemic strokes or TIAs attributable to embolization from the aneurysmal sac were observed for 9 of 269 patients (3.3%) with unruptured aneurysms. Of these nine patients, five were women and four were men (mean age, 62 yr; age range, 45-72 yr). Symptomatic aneurysms were located in the middle cerebral artery (n = 4), internal carotid artery (n = 3), posterior cerebral artery (n = 1), or vertebral artery (n = 1). The mean maximal diameter was 12.5 mm (range, 5-45 mm). Six patients underwent surgical treatment, of whom two experienced postoperative cerebral infarctions referable to the distribution of the artery harboring the aneurysm. Two patients were treated with aspirin, and one patient received no treatment. The mean follow-up period was 38 months (range, 1-60 mo). None of the patients experienced additional ischemic events during the follow-up period. Among the 41 previously reported patients, conservative treatment was used for 20 patients (mean follow-up period, 50.7 +/- 44.5 mo). Four of the 20 patients experienced recurrent TIAs, 1 patient experienced worsening of symptoms, and 1 patient died during the follow-up period. A total of 21 patients underwent surgical treatment (mean follow-up period, 33.6 +/- 32.3 mo). Of these patients, only one experienced recurrent TIAs. Two patients experienced postoperative seizures, and one patient died during the follow-up period. All recurrent symptoms with either surgical or conservative treatment were transient, and no patient experienced a major or disabling stroke during the follow-up period. CONCLUSION Ischemic events can occur distal to both small and large unruptured intracranial aneurysms (predominantly in the anterior circulation). The long-term risk of recurrent ischemic events, particularly major or disabling strokes, seems to be low with either surgical or conservative treatment.