If you’ve been diagnosed with an unruptured brain aneurysm, you likely have questions about how to manage it and if, or when, you should pursue treatment. Working closely with your doctor and a brain aneurysm specialist is essential to navigating the best course of action for your situation.

Unruptured brain aneurysm basics

An unruptured intracranial aneurysm is an abnormal pocket or bulge in a blood vessel in the brain that has not ruptured. Generally, the larger the aneurysm, the higher the risk of rupture. Smaller aneurysms often do not cause symptoms, but larger ones that press on nerves and brain tissue may.

The likelihood of having this type of aneurysm increases with age, affecting around 2% of the overall population and up to 5% of people over 65. 

Although many people live long lives with them, if the aneurysm bursts, it causes bleeding around the brain, known as a subarachnoid hemorrhage. This type of bleeding, which is a type of stroke, can cause severe brain injury or death.

Unruptured brain aneurysms are often found by chance during scans for other medical reasons, due to the widespread use of high-resolution CT angiography and MRI.

“Most patients don’t have symptoms at diagnosis, so the central clinical challenge is determining whether and how to treat an aneurysm that has not yet ruptured,” says neurosurgeon William Thorell, MD. “Management requires a careful assessment of rupture risk, treatment risk, and patient-specific factors, with an emphasis on shared decision-making.”

Read more about how a brain aneurysm is different from a stroke.

Evaluating the risk of rupture

While the majority of unruptured brain aneurysms will never rupture, large observational studies have shown that annual rupture risk is influenced by:

• The size, location, growth and shape of the aneurysm.
• Overall health, age, medications and smoking status.
• Current or previous medical conditions, including high blood pressure.
• Personal or family history of subarachnoid hemorrhage.

Looking at all the risk factors is key.

“Importantly, rupture risk is present throughout a patient’s life, making age and expected longevity key considerations,” says Dr. Thorell. “Generally and with some exceptions, small aneurysms under 7 millimeters in the anterior circulation carry a low annual rupture risk. Larger aneurysms located in the posterior circulation and aneurysms with irregular structure or documented growth have a higher likelihood of rupture. Several scoring systems exist to estimate rupture risk, but none replace clinical judgment.”

Observation management

High-quality vascular imaging is essential once an unruptured brain aneurysm is diagnosed. Ongoing monitoring and imaging are crucial, using magnetic resonance angiograms or CT scans. 

“For many patients, conservative management is appropriate,” adds Dr. Thorell. “This includes ongoing imaging to monitor the aneurysm’s growth and aggressive management of controllable risk factors. Smoking cessation, blood pressure control, and general cardiovascular risk reduction are cornerstones of non-operative care. Observation is particularly favored in older patients, those with significant medical conditions, or those with small, stable aneurysms in low-risk locations.”

Imaging is often performed at six to 12 months, then at longer intervals if the aneurysm remains stable. When treatment is being considered or the anatomy is complex, catheter angiography may be used.

Treatment: Balancing risk

Individualized care and shared decision-making with a brain aneurysm specialist are essential when considering treatment. Both observation and treatment carry risks. If an unruptured aneurysm shows growth or other concerning changes, a specialist may discuss the risks and benefits of treatment.

“Management of unruptured intracranial aneurysms is fundamentally about balancing the risk between rupture and treatment,” says Dr. Thorell. “The aneurysm’s anatomy, the patient’s age, health and individual risk factors, medical expertise and patient wishes all need to be considered. When rupture risk is felt to outweigh treatment risk, intervention may be recommended.” 

Nebraska Medicine neurosurgeons perform several endovascular and microsurgical techniques that can treat an unruptured aneurysm or repair a promptly detected ruptured aneurysm. 

Two primary treatment strategies include:

• Open surgery (craniotomy): Surgeons place a clip at the base of the aneurysm, known as microsurgical clipping.

• Endovascular therapy: This includes coiling, the WEB device and flow diversion. Minimally invasive coiling involves threading a catheter through blood vessels to place tiny coils in the aneurysm. This causes clotting, stops blood flow and prevents further rupture of the vessels. Long-term antiplatelet therapy and ongoing imaging surveillance may be required.

Nebraska Medical Center has a dedicated Neuroscience Intensive Care Unit for patients with a ruptured brain aneurysm after surgery. This specialized unit is crucial for monitoring and treating potential complications that can occur in the days and weeks after a rupture.