What is a brain aneurysm?

A brain aneurysm is like a blister, bubble or pocket that occurs in the wall of one of the brain's blood vessels. When a vessel walls gets weak, it can start to stretch out and make a bubble. Eventually, that bubble can rupture and cause bleeding—called a hemorrhage—in the brain.

Symptoms of a brain aneurysm

A tricky aspect of a brain aneurysm is that it often doesn't cause any symptoms unless it ruptures or gets big enough to push against a nerve. You may not know it's there unless it's found during another test, like an MRI. If an aneurysm gets large enough to press on a nerve, you may notice symptoms like:

  • One dilated pupil
  • Numbness on one side of the body
  • Pain above one eye
  • A drooping eyelid on one side

Other problems can look or feel the same way, but if you have these symptoms, talk to your doctor. Catching an aneurysm before it ruptures can make a big difference. When an aneurysm is about to rupture, common symptoms include:

  • The worst headache you've ever had
  • Weakness or numbness
  • Loss of consciousness

A ruptured aneurysm is an emergency. Get medical attention immediately for anyone experiencing these symptoms.

Diagnosis and testing for a brain aneurysm

Diagnosing an aneurysm starts with talking to your doctor about the history of your symptoms and doing a physical exam. From there, you'll have imaging studies, like a CT scan or MRI. Your doctor may also recommend a screening called magnetic resonance angiography (MRA). This is an imaging test like an MRI that looks specifically at the blood vessels. You might also need an angiogram or digital subtraction angiography, which study your blood vessels.

Brain aneurysm treatment options

If these tests find an aneurysm, treatment depends on whether it has ruptured. If it hasn't, you can either have your doctor monitor it or choose to undergo surgery to remove it before it causes problems. If the aneurysm has ruptured, surgery is necessary to fix it. There are two main types of aneurysm surgery:

  • Craniotomy: This surgery opens a part of the skull so that a neurosurgeon can insert a small clip to block blood flow to the aneurysm. Blocking the blood flow relieves the pressure on the blood vessel wall.
  • Coiling: Also called coil embolization, this is a non-invasive procedure where a surgeon guides a small coil through the blood vessels until it reaches the aneurysm. Once it gets there, it plugs the aneurysm permanently and restores normal blood flow.

A brain aneurysm isn't a health problem to take lightly. Talk to your doctor today if you're experiencing symptoms.

Brain Aneurysm Clipping

Main Line Health offers brain aneurysm clipping to help prevent an aneurysm from life-threatening rupture.


Endovascular Coiling for Treating Hemorrhagic Stroke

If left untreated, hemorrhagic stroke can result in serious neurological deficits or death. Endovascular Coiling is one of the procedures offering new hope to hemorrhagic stroke patients who had been told previously that they had no further treatment options.

Hemorrhagic Stroke Treatment

Endovascular coiling, also called coiling or endovascular embolization, is a procedure performed to block blood flow into an aneurysm (a weakened area in the wall of an artery).

Ischemic Stroke Treatment

There are many ways that the specialists at Main Line Health can treat ischemic strokes.

Stroke Rehab

Inpatient and outpatient stroke rehabilitation treatment and complex stroke treatment. We develop a unique stroke rehab therapy plan that help patients immediately build on their strengths and learn to compensate for limitations.


Thrombectomy is an advanced stroke treatment offered at Bryn Mawr Hospital. It may be performed up to 24 hours after first stroke symptoms.



Discover how Main Line Health neurosurgeons provide expert care, from routine to complex spinal and nervous system conditions for patients.


The neurology team at Main Line Health treats and manages conditions such as migraines, multiple sclerosis, Parkinson’s disease and more.

Stroke and Neurointervention

Main Line Health is one of few community health systems offering state-of-the-art neurointervention care. Through our collaboration with the Jefferson Hospital for Neuroscience, our Neurointervention Program is an accredited thrombectomy-capable stoke center.

Emergency Medicine

Take comfort in knowing that the Emergency Care Team at Main Line Health is here for you when you need us most to provide compassionate care as quickly as possible.

Pain Management

Discover how Main Line Health experts serve Philadelphia by treating a wide range of conditions, including back, neck and oncology-related pain.