Advances in vascular surgery.

Aneurysms Unruptured Aneurysms The first report of the International Study of Unruptured Intracranial Aneurysms (ISUIA) cited very low rates of subarachnoid hemorrhage (SAH) for previously unruptured aneurysms.1 Data were collected retrospectively. It was difficult to reconcile these rates with those reported from prior studies, with the known sizes of ruptured aneurysms and with clinical experience. Prior reports including prospective studies suggested that unruptured aneurysms carried a 1% to 2% risk of hemorrhage per year.2–4 The second report from the ISUIA prospectively enrolled 4060 patients with unruptured aneurysms.5 Of these, 1692 had no intervention for their aneurysm, 1917 had open surgery, and 451 had endovascular procedures. The rupture rates were more in agreement with prior studies (Table). Risk factors for SAH were increasing aneurysm size and aneurysm location at the basilar apex or posterior communicating artery. The risk of surgical repair increased significantly with increasing patient age, posterior circulation location of the aneurysm, history of ischemic cerebrovascular disease, and presence of symptoms from the aneurysm. Thirty-day mortality occurred in 1.5%, morbidity in 3%, poor cognitive function plus morbidity (a Rankin score of 3 to 5) in 4%, and overall total morbidity and mortality in 13%. The data indicate that the decision to treat a ruptured aneurysm needs to include a careful analysis of the patient, their risk factors for poor outcome, and the features of the aneurysm. Endovascular treatment is an option, although overall complete obliteration rates were only about 50% in this study, and risk of treatment was similar to but lower than with surgery, although the groups were not randomized to treatment and are thus not comparable. The findings of the initial results of ISUIA that were at variance with prior assumptions about unruptured aneurysms prompted an exhaustive review of the literature that suggested some explanations for the findings.6 Numerous assumptions and biases inherent in the retrospective design of the first study were cited. An important one is that selection bias could account for the finding that 10 mm seemed to be the cutoff for rupture, yet this is at odds with the fact that the average size of a ruptured aneurysm is 8 mm. The distribution of cases included in the initial cohort will strongly influence the size cutoff for rupture that is found. To take an extreme example, if one collects only aneurysms 10 mm in diameter, then one will necessarily conclude that the cutoff for rupture is some value 10 mm. The author recommended that unruptured aneurysms with clinical pathological profiles resembling those of ruptured lesions be considered for treatment at a smaller size than unruptured lesions with profiles typical of intact aneurysms. The question of whether and how to follow patients with unruptured aneurysms that are not treated is unanswered, but it was felt that periodic radiological imaging might be wise. Screening for aneurysms in asymptomatic patients is only recommended for patients with a strong family history of aneurysms or those with diseases associated with aneurysms such as autosomal dominant polycystic kidney disease. Although it is not proven that cessation of cigarette smoking will alter the natural history of an aneurysm, it would seem obvious to recommend stopping smoking in patients with aneurysms who do smoke. Predicting which patients will suffer morbidity or mortality after surgery for unruptured aneurysms would be helpful. A single surgeon’s operative experience with 387 patients found that the risk of complications increased with increasing aneurysm size, broad neck, plaque or calcification at the neck of the aneurysm, temporary clipping, multiple aneurysms, need for repositioning of the clip, or multiple clips.7 Some of these factors cannot be predicted preoperatively of course, although it was suggested that surgeons carefully consider these factors preoperatively and consider obtaining highresolution computed tomography (CT) through the aneurysm neck if there is suspicion about the condition of the neck, in addition to considering other factors previously identified to be associated with risk of complications such as aneurysm location and preexisting cerebrovascular disease. What are the risk factors for development of a saccular cerebral aneurysm? Traditional factors include age, female sex, some rare inherited conditions, family history, heavy alcohol intake, and hypertension.8–10 A multivariable analysis of 312 patients with SAH and 618 controls determined that current cigarette smoking, history of hypertension, lower body mass index, family history of hemorrhagic stroke, caffeine in pharmaceutical products, lower educational achievement, and nicotine in pharmaceutical products were significant, independent risk factors for SAH.11 A literature review of 20 studies found that significant risk factors for SAH were smoking, hypertension, and drinking 150 g or more of alcohol per week.12 Genes definitively associated with intracranial aneurysms have not been identified. One study in a Japanese cohort identified a locus associated with intracranial aneurysms on The opinions expressed in this editorial are not necessarily those of the editors or of the American Stroke Association. Received December 1, 2003; accepted December 3, 2003. From the Section of Neurosurgery, Department of Surgery, University of Chicago Medical Center and Pritzker School of Medicine, Chicago, Ill. Correspondence and reprint requests to R. Loch Macdonald, MD, PhD, Section of Neurosurgery, MC3026 University of Chicago Medical Center 5841 South Maryland Ave, Chicago, IL 60637. E-mail [email protected] (Stroke. 2004;35:375-380.) © 2004 American Heart Association, Inc.