patients with no history of SAH from another aneurysm worsened clinical outcomes; treatment of unruptured aneurysms that were larger, symptomatic, or in patients with a history of SAH was cost effective [88]. Aneurysm location was not considered in this analysis. https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 12/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate A later decision and cost-effectiveness analysis used the 2003 ISUIA data and compared surgical or endovascular treatment with no treatment for unruptured intracranial aneurysms [89]. The following observations were reported: For 50-year-old patients, treatment was ineffective or not cost effective for aneurysms with the following characteristics: Small (<7 mm), due to the low risk of rupture Located in the cavernous carotid artery Large (>25 mm) and located in the posterior circulation, due to the high risk of complications from treatment For 40-year-old patients, treatment was ineffective or not cost effective for aneurysms with the following characteristics: Small (<12 mm) or large (>25 mm) and located in the cavernous carotid artery Small (<7 mm) and located in the anterior circulation Indications for intervention The available studies emphasize the need to examine each case individually, considering factors such as comorbid medical illness, patient age, aneurysm size and location, and risks of treatment. The sum of these data supports expectant management of very small saccular aneurysms, particularly when such aneurysms are located in the anterior circulation or when they are detected in older patients. A task force of the Stroke Council of the American Heart Association published recommendations (also prior to the 2003 ISUIA data) for the management of patients with an unruptured intracranial aneurysm that are similar to the above recommendations [90]: The treatment of small incidental intracavernous internal carotid artery aneurysms is generally not indicated. For large symptomatic intracavernous aneurysms, treatment decisions should be individualized on the basis of patient age, severity and progression of symptoms, and treatment alternatives. The higher risk of treatment and shorter life expectancy in older individuals must be considered in all patients, and it favors observation in older patients with asymptomatic aneurysms. Symptomatic intradural aneurysms of all sizes should be considered for treatment with relative urgency. https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 13/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate Coexisting or remaining aneurysms of all sizes in patients with an SAH due to another treated aneurysm warrant consideration for treatment. Aneurysms located at the basilar apex carry a relatively high risk of rupture. Treatment decisions must take into account the patient's age, existing medical and neurologic condition, and relative risks of repair. If a decision is made for observation, reevaluation on a periodic basis with computed tomography angiography (CTA)/magnetic resonance angiography (MRA) or selective contrast angiography should be considered, with changes in aneurysmal size sought, although careful attention to technical factors will be required to optimize the reliability of these measures. Given the apparent low risk of hemorrhage from incidental, small (<7 mm) aneurysms in patients without previous SAH, observation rather than intervention is generally advocated. However, special consideration for treatment should be given to young (<50 years) patients in this group. Asymptomatic aneurysms 7 to 10 mm in diameter warrant strong consideration for treatment, taking into account patient age, existing medical and neurologic conditions, and relative risks for treatment [91]. Choice of procedure Surgical treatment of unruptured aneurysms has been the most common procedure used in patients who undergo definitive therapy. In clinical studies, which are typically in centers with high case volumes, endovascular techniques appear to be associated with lower morbidity and mortality than surgical clipping and are playing an increasing role in the treatment of unruptured aneurysms [92-96]. (See "Treatment of cerebral aneurysms", section on 'Patients with unruptured aneurysms'.) New technologies, such as flow diversion, may advance the safety of endovascular treatment and allow aneurysms, previously considered to be inaccessible or technologically difficult for such treatment, to undergo treatment [97]. Special situations With AVM Rare patients have an intracranial aneurysm associated with an intracranial arteriovenous malformation (AVM). These aneurysms are more likely to be associated with growth and rupture than aneurysms in general [98]. Therefore, repairing the aneurysm prior to treating the AVM is recommended. Carotid stenosis One study found that intracranial aneurysms appeared to be more common than expected in a population of patients with symptomatic carotid artery disease, perhaps because of shared risk factors [99]. Aneurysms distal to a symptomatic cervical internal https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 14/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate carotid artery stenosis may be susceptible to sudden hemodynamic changes with carotid endarterectomy (CEA) that could lead to aneurysmal rupture [44]. On the other hand, surgical clipping of an aneurysm distal to a severe internal carotid stenosis may increase the risk of ischemic stroke. Unfortunately, data for this situation are too sparse to allow firm conclusions as to which problem should be tackled first. However, caution is advised if CEA is performed in this setting, especially if the unruptured ipsilateral aneurysm is 7 mm or larger in diameter or if there is a history of SAH from another aneurysm. Use of antithrombotic therapy Patients with intracranial aneurysms may require antithrombotic therapy for the management of other conditions such as atrial fibrillation. The available data are limited, somewhat conflicting, and not sufficient to determine whether anticoagulant (eg, warfarin) or antiplatelet therapy increases the risk of aneurysm rupture. [100]. Anticoagulant therapy does appear to increase the severity of rupture should it occur. The available data regarding the risks of antithrombotic therapy in patients with unruptured aneurysm are discussed in detail separately. (See "Anticoagulant and antiplatelet therapy in patients with an unruptured intracranial aneurysm".) Monitoring For patients with unruptured intracranial aneurysms that are not treated with open surgery or endovascular methods, the following recommendations are made for monitoring [44]: We suggest that unruptured intracranial aneurysms be monitored with CTA or MRA annually for two to three years, and every two to five years thereafter if the aneurysm is clinically and radiographically stable [44]. However, it is not unreasonable to obtain the first reimaging study of newly detected small aneurysms at six months, since there is evidence that newly formed small aneurysms may be at higher risk of rupture than older, more stable aneurysms (see 'Aneurysm growth and rupture' above). Longer reimaging intervals are certainly appropriate if the six-month study shows no significant change. Patients should be instructed to avoid smoking, heavy alcohol consumption, stimulant medications, illicit drugs, and excessive straining and Valsalva maneuvers. Patients whose aneurysm is treated are at risk for recurrent aneurysm formation and require monitoring. This is discussed in detail separately. (See "Late recurrence of subarachnoid hemorrhage and intracranial aneurysms".) https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 15/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topic (see "Patient education: Brain aneurysm (The Basics)") SUMMARY AND RECOMMENDATIONS In the general population, the prevalence of unruptured intracranial aneurysms is estimated to be approximately 3 percent. A higher risk of intracranial aneurysm formation occurs in certain genetic syndromes including Ehlers-Danlos syndrome, polycystic kidney disease (PKD), and others. Apart from these genetic syndromes, a family history of intracranial aneurysm is also a risk factor. Nongenetic risk factors include hypertension and cigarette smoking. Most unruptured aneurysms present as an incidental finding on a neuroimaging study or in screening. Occasionally, aneurysms can produce compressive symptoms such as a third cranial nerve palsy. Magnetic resonance angiography (MRA) and computed tomography angiography (CTA) appear to be able to detect aneurysms 5 mm or larger. Conventional angiography is more sensitive, but carries procedural risks. The most common treatments for aneurysms are surgical clipping and endovascular coiling. Indications for intervention take into account the risk of aneurysm rupture. In general, we suggest treatment of most nonintracavernous intracranial aneurysms that are greater than https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 16/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate 7 to 10 mm in size, while observation and monitoring is suggested for smaller aneurysms. Patients with an intracranial aneurysm should be monitored for aneurysm growth, aneurysm recurrence, and new aneurysm formation. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Etminan N, Rinkel GJ. 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Stroke https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 23/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate 2009; 40:1341. 100. Hasan DM, Mahaney KB, Brown RD Jr, et al. Aspirin as a promising agent for decreasing incidence of cerebral aneurysm rupture. Stroke 2011; 42:3156. Topic 1132 Version 14.0 https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 24/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate GRAPHICS Unruptured small basilar tip aneurysm on MRA A 3D time of flight MRA, shows a 4 mm basilar tip aneurysm (arrow). Image B is a magnified view and shows the small unruptured aneurysm (arrow). MRA: magnetic resonance angiogram. Graphic 93978 Version 1.0 https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 25/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate Sensitivity of CTA for intracranial aneurysms The graph shows the increasing sensitivity of CTA with increasing aneurysm size. Points represent the median, and error bars represent the 95 percent confidence limits. Aneurysms greater than 10 mm have been pooled. Data from: van Gelder, JM. Computed tomographic angiography for detecting cerebral aneurysms: implications of aneurysm size distribution for the sensitivity, speci city, and likelihood ratios. Neurosurgery 2003; 53:597. Graphic 81565 Version 2.0 https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 26/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate False-positive intracranial aneurysms reported by CTA Bars represent the number of reported aneurysms of each size from 199 false-positive reports of aneurysms. Data from: van Gelder, JM. Computed tomographic angiography for detecting cerebral aneurysms: implications of aneurysm size distribution for the sensitivity, speci city, and likelihood ratios. Neurosurgery 2003; 53:597. Graphic 69728 Version 1.0 https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 27/28 7/7/23, 11:37 AM Unruptured intracranial aneurysms - UpToDate Contributor Disclosures Robert J Singer, MD No relevant financial relationship(s) with ineligible companies to disclose. Christopher S Ogilvy, MD Consultant/Advisory Boards: Cerevasc [Hydrocephalus]; Contour [Aneurysms]; Medtronic [Chronic subdural hematoma]. All of the relevant financial relationships listed have been mitigated. Guy Rordorf, MD No relevant financial relationship(s) with ineligible companies to disclose. Jos Biller, MD, FACP, FAAN, FAHA No relevant financial relationship(s) with ineligible companies to disclose. Janet L Wilterdink, MD No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/unruptured-intracranial-aneurysms/print 28/28