Brain Aneurysm
A brain aneurysm, also known as a cerebral or intracranial aneurysm, is a weakened, bulging area in the wall of a blood vessel in the brain. This balloon-like protrusion can leak or rupture, causing bleeding into the surrounding brain tissue, a life-threatening emergency known as a subarachnoid hemorrhage.
What is it?
A brain aneurysm forms when a section of an artery wall weakens and balloons outward, creating a thin-walled sac filled with blood. Most brain aneurysms are saccular (berry-shaped), with a narrow neck connecting to the parent artery, though fusiform (spindle-shaped) aneurysms also occur. These weaknesses typically develop at arterial branch points where blood flow creates increased stress on vessel walls. The exact cause is often multifactorial, involving both genetic predisposition and acquired risk factors.
Brain aneurysms affect approximately 3-5% of the general population, though most remain unruptured and asymptomatic throughout a person’s lifetime. They occur more frequently in adults aged 30-60 and are more common in women than men. Risk factors include smoking, high blood pressure, family history, certain genetic conditions (polycystic kidney disease, Ehlers-Danlos syndrome), and previous aneurysm rupture. About 85% of aneurysms occur in the anterior circulation, particularly at the Circle of Willis. While most aneurysms never rupture, those that do cause subarachnoid hemorrhage, which carries a mortality rate of 40-50%, with many survivors experiencing permanent neurological deficits.
Important to Know
Most unruptured brain aneurysms are discovered incidentally during imaging for other reasons. The decision to treat an unruptured aneurysm involves carefully weighing the risk of rupture against the risks of treatment. Factors considered include aneurysm size, location, shape, patient age, family history, and symptoms. Small aneurysms (less than 7mm) in the anterior circulation without concerning features may be monitored with serial imaging. Treatment options include endovascular coiling (threading a catheter through blood vessels to fill the aneurysm with coils), surgical clipping (placing a metal clip across the aneurysm neck), or flow diversion devices. A ruptured aneurysm is a medical emergency requiring immediate hospitalization and treatment. Warning signs of rupture include sudden, severe “thunderclap” headache, neck stiffness, nausea, vision changes, loss of consciousness, or seizures. If you experience these symptoms, seek emergency care immediately.