What “Unruptured” Actually Means for a Brain Aneurysm

September is Brain Aneurysm Awareness Month, and Jenny P. Tsai, M.D., an associate professor of neurology at Cleveland Clinic Lerner College of Medicine specializing in neuroendovascular intervention and vascular neurology, wants people to understand what an aneurysm actually is before fear takes over. She describes it as a bubble forming on the side of a normal blood vessel in the brain, a weak spot in what should otherwise be a sturdy system of pipes carrying blood to the brain.

Most aneurysms grow very slowly over years, Tsai said. They don’t bleed and don’t press on surrounding structures, so they often stay completely silent. The real danger lies in the fact that some behave benignly for a lifetime while others carry a risk of rupture, the point at which an aneurysm breaks open and becomes dangerous.

The headache that feels like a baseball bat

Tsai said brain aneurysms can sometimes cause a small leak before a full rupture, meaning a person might feel fine one moment and then experience a sudden, severe headache, what’s known in medical literature as a “thunderclap headache.” She described it as feeling like being suddenly struck by lightning, or as if someone sneaked up behind you and hit you in the head with a baseball bat. It often comes with a painful, stiff neck.

That headache is typically followed by severe nausea and vomiting, and some people experience confusion, loss of consciousness or stroke-like symptoms. The stakes are high: Tsai said an estimated 15% of people with a ruptured aneurysm don’t make it to the hospital, and nearly one in four die within the first 24 hours without treatment. Because roughly 15% of survivors can experience repeat bleeding, which is often devastating, treatment typically needs to happen within that first 24-hour window.

How doctors decide: Monitor or treat

For aneurysms discovered incidentally, before any rupture, Tsai said the decision between monitoring and treatment comes down to a detailed risk assessment. Modern brain imaging allows doctors to closely evaluate an aneurysm’s location, size and shape, along with risk factors specific to the patient. For smaller aneurysms where the risk of bleeding is lower than the risk of treatment itself, the priority becomes ongoing monitoring for stability, paired with efforts to reduce the factors that contribute to growth or rupture.

The risk factors patients can control

Tsai identified tobacco use and high blood pressure as the two most significant modifiable risk factors tied to aneurysm growth and rupture, and said correcting them is one of the most important interventions for any patient diagnosed with a brain aneurysm. Other risk factors are harder to change: women from their mid-50s to 60s and older face a higher rupture risk, as do people with a family history of brain aneurysms or connective tissue disorders, conditions in which blood vessel walls are inherently weaker than average.

The message for this awareness month

Tsai acknowledged that brain aneurysms carry a frightening reputation, and can genuinely be life-altering. But she emphasized that several million people in the U.S. live with a brain aneurysm, and the most important step after a diagnosis is simple: see a doctor, get a clear understanding of the specific aneurysm’s risk, and know that with proper care, most people are going to be fine.