What is the risk of coincidental cerebral aneurysm (cerebral artery aneurysm) rupture?

From the Guidelines

The risk of coincidental cerebral aneurysm rupture is approximately 0.05%/y for small aneurysms (< 10 mm in diameter) and ~1%/y for larger aneurysms (≥ 10 mm in diameter), with the risk increasing to 6% in the first year for giant aneurysms (≥ 25 mm) 1. This risk is significantly higher in patients with multiple risk factors such as smoking, hypertension, family history of aneurysms, or certain genetic conditions like polycystic kidney disease. The cumulative lifetime risk increases with age, and women have a slightly higher risk than men. When an aneurysm ruptures, it causes a subarachnoid hemorrhage, which has a mortality rate of about 40-50%, with approximately one-third of survivors experiencing significant neurological deficits. For patients with known unruptured aneurysms, regular monitoring with imaging (typically MRA or CTA every 6-12 months initially, then potentially less frequently if stable) is essential. Blood pressure control is crucial, with a target of less than 140/90 mmHg using appropriate antihypertensive medications. Complete smoking cessation and limiting alcohol consumption are strongly recommended. The decision between observation and prophylactic treatment (surgical clipping or endovascular coiling) depends on aneurysm characteristics, patient age, overall health status, and should be made in consultation with a neurosurgeon or neurointerventionalist. Key factors to consider in the management of unruptured intracranial aneurysms include size, location, and other morphological characteristics of the aneurysm, documented growth on serial imaging, patient age, history of prior subarachnoid hemorrhage, family history of cerebral aneurysm, presence of multiple aneurysms, and concurrent pathology 1. Endovascular coiling can be effective and is associated with a reduction in procedural morbidity and mortality over surgical clipping in selected cases 1. However, the most recent and highest quality study, which is the guideline for healthcare professionals from the American Heart Association/American Stroke Association, published in 2015, should be prioritized when making a definitive recommendation 1. Some key points from this guideline include:

• Several factors should be considered in the selection of the optimal management of a UIA, including size, location, and other morphological characteristics of the aneurysm, documented growth on serial imaging, patient age, history of prior subarachnoid hemorrhage, family history of cerebral aneurysm, presence of multiple aneurysms, and concurrent pathology.
• Patients with unruptured cerebral aneurysms who are considered for treatment should be fully informed about the risks and benefits of both endovascular and microsurgical treatment as alternatives to secure the UIAs and prevent bleeding.
• The results of UIA treatment are inferior at low-volume centers, and hence treatment is recommended to be performed at higher-volume centers. Considering the evidence, the management of unruptured intracranial aneurysms should be individualized, taking into account the size, location, and other characteristics of the aneurysm, as well as patient age, medical comorbidities, and other relevant factors, with the goal of minimizing the risk of rupture and improving outcomes 1.

From the Research

Risk of Coincidental Cerebral Aneurysm Rupture

• The annual risk of rupture for brain aneurysms is considered to be relatively low 2
• However, if a rupture occurs, it can lead to significant morbidity and mortality 2
• The natural history and treatment outcomes of cerebral aneurysms have increased over the last few decades, but management requires careful consideration of various medical, clinical, and anatomic factors 2

Factors Influencing Rupture Risk

• The risk of rupture is influenced by various factors, including the size and location of the aneurysm, as well as the presence of other medical conditions 2
• Vasospasm is a major cause of morbidity and mortality in patients after aneurysmal subarachnoid hemorrhage, and early treatment of ruptured aneurysms is advocated to prevent delayed intervention and complications 3

Treatment and Management

• Treatment options for cerebral aneurysms include endovascular coiling and clipping, as well as medical management with medications such as nimodipine to prevent cerebral vasospasm 4, 5, 6
• Intra-arterial nimodipine infusion has been shown to be effective in reducing cerebral vasospasm and improving clinical outcomes in patients with aneurysmal subarachnoid hemorrhage 5
• Prophylactic administration of nimodipine has been found to reduce the rate of cerebral vasospasm and delayed cerebral ischemia in patients treated with endovascular coiling 6