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      An overview of intracranial aneurysms

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      McGill Journal of Medicine : MJM
      McGill University

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          Abstract

          Intracranial aneurysms are relatively common, with a prevalence of approximately 4%. Unruptured aneurysms may cause symptoms mainly due to a mass effect, but the real danger is when an aneurysm ruptures, leading to a subarachnoid hemorrhage. Most aneurysms are asymptomatic and will not rupture, but they grow unpredictably and even small aneurysms carry a risk of rupture. Intracranial aneurysms are diagnosed and monitored with imaging including intra-arterial digital subtraction angiography, computed tomography angiography, magnetic resonance angiography, and recently transcranial Doppler ultrasonograpy has been proposed as a potential modality. Treatment options include observation, endovascular coiling, and surgical clipping. This paper will review the epidemiology, pathogenesis, clinical presentation, diagnosis, natural history, and management of unruptured saccular intracranial aneurysms.

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          Most cited references24

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          Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment.

          The management of unruptured intracranial aneurysms is controversial. Investigators from the International Study of Unruptured Intracranial Aneurysms aimed to assess the natural history of unruptured intracranial aneurysms and to measure the risk associated with their repair. Centres in the USA, Canada, and Europe enrolled patients for prospective assessment of unruptured aneurysms. Investigators recorded the natural history in patients who did not have surgery, and assessed morbidity and mortality associated with repair of unruptured aneurysms by either open surgery or endovascular procedures. 4060 patients were assessed-1692 did not have aneurysmal repair, 1917 had open surgery, and 451 had endovascular procedures. 5-year cumulative rupture rates for patients who did not have a history of subarachnoid haemorrhage with aneurysms located in internal carotid artery, anterior communicating or anterior cerebral artery, or middle cerebral artery were 0%, 2. 6%, 14 5%, and 40% for aneurysms less than 7 mm, 7-12 mm, 13-24 mm, and 25 mm or greater, respectively, compared with rates of 2 5%, 14 5%, 18 4%, and 50%, respectively, for the same size categories involving posterior circulation and posterior communicating artery aneurysms. These rates were often equalled or exceeded by the risks associated with surgical or endovascular repair of comparable lesions. Patients' age was a strong predictor of surgical outcome, and the size and location of an aneurysm predict both surgical and endovascular outcomes. Many factors are involved in management of patients with unruptured intracranial aneurysms. Site, size, and group specific risks of the natural history should be compared with site, size, and age-specific risks of repair for each patient.
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            International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial.

            Endovascular detachable coil treatment is being increasingly used as an alternative to craniotomy and clipping for some ruptured intracranial aneurysms, although the relative benefits of these two approaches have yet to be established. We undertook a randomised, multicentre trial to compare the safety and efficacy of endovascular coiling with standard neurosurgical clipping for such aneurysms judged to be suitable for both treatments. We enrolled 2143 patients with ruptured intracranial aneurysms and randomly assigned them to neurosurgical clipping (n=1070) or endovascular treatment by detachable platinum coils (n=1073). Clinical outcomes were assessed at 2 months and at 1 year with interim ascertainment of rebleeds and death. The primary outcome was the proportion of patients with a modified Rankin scale score of 3-6 (dependency or death) at 1 year. Trial recruitment was stopped by the steering committee after a planned interim analysis. Analysis was per protocol. 190 of 801 (23.7%) patients allocated endovascular treatment were dependent or dead at 1 year compared with 243 of 793 (30.6%) allocated neurosurgical treatment (p=0.0019). The relative and absolute risk reductions in dependency or death after allocation to an endovascular versus neurosurgical treatment were 22.6% (95% CI 8.9-34.2) and 6.9% (2.5-11.3), respectively. The risk of rebleeding from the ruptured aneurysm after 1 year was two per 1276 and zero per 1081 patient-years for patients allocated endovascular and neurosurgical treatment, respectively. In patients with a ruptured intracranial aneurysm, for which endovascular coiling and neurosurgical clipping are therapeutic options, the outcome in terms of survival free of disability at 1 year is significantly better with endovascular coiling. The data available to date suggest that the long-term risks of further bleeding from the treated aneurysm are low with either therapy, although somewhat more frequent with endovascular coiling.
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              Prevalence and risk of rupture of intracranial aneurysms: a systematic review.

              The estimates on the prevalence and the risk of rupture of intracranial saccular aneurysms vary widely between studies. We conducted a systematic review on prevalence and risk of rupture of intracranial aneurysms and classified the data according to study design, study population, and aneurysm characteristics. We searched for studies published between 1955 and 1996 by means of a MEDLINE search and a cumulative review of the reference lists of all relevant publications. Two authors independently assessed eligibility of all studies and extracted data on study design and on numbers and characteristics of patients and aneurysms. For data on prevalence we found 23 studies, totalling 56,304 patients; 6685 (12%) of these patients were from 15 angiography studies. Prevalence was 0.4% (95% confidence interval, 0.4% to 0.5%) in retrospective autopsy studies, 3.6% (3.1 to 4.1) for prospective autopsy studies, 3.7% (3.0 to 4.4) in retrospective angiography studies, and 6.0% (5.3 to 6.8) in prospective angiography studies. For adults without specific risk factors, the prevalence was 2.3% (1.7 to 3.1); it tended to increase with age. The prevalence was higher in patients with autosomal dominant polycystic kidney disease (relative risk [RR], 4.4 [2.7 to 7.2]), a familial predisposition (RR, 4.0 [2.7 to 6.0]), or atherosclerosis (RR, 2.3 [1.7 to 3.1]). Only 8% (5 to 11) of the aneurysms were >10 mm. For the risk of rupture, we found nine studies, totalling 3907 patient-years. The overall risk per year was 1.9% (1.5 to 2.4); for aneurysms = 10 mm, the annual risk was 0.7% (0.5 to 1.0). The risk was higher in women (RR, 2.1[1.1 to 3.9]) and for aneurysms that were symptomatic (RR, 8.3 [4.0 to 17]), >10 mm (RR, 5.5 [3.3 to 9.4]), or in the posterior circulation (RR, 4.1 [1.5 to 11]). Data on prevalence and risk of rupture vary considerably according to study design, study population, and aneurysm characteristics. If all available evidence with inherent overestimation and underestimation is taken together, for adults without risk factors for subarachnoid hemorrhage, aneurysms are found in approximately 2%. The vast majority of these aneurysms are small (=10 mm) and have an annual risk of rupture of approximately 0.7%.
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                Author and article information

                Journal
                Mcgill J Med
                9710939
                McGill Journal of Medicine : MJM
                McGill University
                1201-026X
                July 2006
                : 9
                : 2
                : 141-146
                Author notes
                *To whom correspondence should be addressed: Alexander Keedy, akeedy@ 123456uci.edu

                Alexander Keedy completed his undergraduate training at Santa Clara University and is currently a third year medical student at University of California, Irvine (UCI). His research interests include the diagnostic accuracy of CT in cirrhosis and the clinical utility and applications of 3D CT reconstructions. He will postpone his fourth year of medical school for one year in order to work on a project to determine the efficacy of teaching anatomy and radiology with three dimensional displays at UCSF.

                Article
                mjm0902p141
                10.26443/mjm.v9i2.672
                2323531
                18523626
                b2cf40ec-cdb0-4d2c-ab78-782a928f08dd
                Copyright © 2006 by MJM

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License, which permits for noncommercial use, distribution, and reproduction in any digital medium, provided the original work is properly cited and is not altered in any way. For details, please refer to http://creativecommons.org/licenses/by-nc-nd/3.0/

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