Subarachnoid Hemorrhage

An aneurysm is a weakened area in a blood vessel that’s at risk of rupturing. When the aneurysm is located in the brain, it's called a cerebral, intracerebral, or intracranial aneurysm. A cerebral aneurysm often develops over a long period of time and may not cause any symptoms before it bursts or ruptures. Most aneurysms develop after age 40.  

A subarachnoid hemorrhage means that there is bleeding in the space that surrounds the brain. Most often, it occurs when an aneurysm that's located on the outer surface of the brain bursts and leaks blood around the brain and inside the skull. The blood that pools around the brain after a subarachnoid hemorrhage can increase the pressure on the brain, which may cause brain cell damage and life-long complications and disabilities.

Facts about subarachnoid hemorrhage

A subarachnoid hemorrhage may be a complication of one of two types of stroke—a hemorrhagic stroke. The other type of stroke is called an ischemic stroke, which is caused by a blood clot in the brain. An intracerebral hemorrhage is a hemorrhagic stroke, which leads to bleeding inside the brain. This bleeding can sometimes dissect through the brain and rupture into the subarachnoid space, either through the surface of the brain or into a ventricle, leading to subarachnoid hemorrhage.

Even though a subarachnoid hemorrhage leads to bleeding outside of the brain, it can still be life-threatening, because the blood from the hemorrhage can compress vital portions of the brain or cause herniation. A severe hemorrhage can cause a coma, or leave you paralyzed. In some cases, however, the ruptured brain aneurysm may stop bleeding on its own before it causes a lot of damage.


Although a brain aneurysm may not cause symptoms, a subarachnoid hemorrhage does. Common symptoms include:

  • Loss of consciousness

  • Double vision

  • Nausea and/or vomiting

  • Severe headache—the worst headache pain you've ever had that feels different from other headaches

  • Trouble speaking

  • Drooping eyelid

  • Confusion and difficulty concentrating

  • Sensitivity to light

  • Neck stiffness

  • Seizures

Before a subarachnoid hemorrhage occurs, a large brain aneurysm that's started to push against nerves in the brain can cause symptoms, such as:

  • Pain surrounding the eye

  • Changes in your vision

  • Dilated pupils

  • Weakness or numbness on one side of your body

  • Loss of hearing or trouble with balance

  • Seizures

  • Difficulty with memory


If you have symptoms of a subarachnoid hemorrhage, a doctor might use several tests to diagnose it:

  • CT scan or MRI scan to examine the brain tissue

  • Angiogram to evaluate the blood vessels in the brain

  • Spinal tap to analyze the cerebrospinal fluid for the presence of blood

A diagnosis of a cerebral aneurysm isn't usually made until a subarachnoid hemorrhage has already occurred.


A subarachnoid hemorrhage is a medical emergency, and immediate treatment is essential to help reduce the risk for permanent brain damage. The main goal of treating a subarachnoid hemorrhage is to stop the bleeding. Often, a doctor may perform surgery to place a small clip on the blood vessel to stop blood from leaking into the brain.

Alternatively, some types of aneurysms can be treated with an endovascular coil, either by a radiologist or neurosurgeon.  This requires making a tiny incision in your thigh and passing a thin catheter through the artery in your leg up to the artery in your head that is bleeding. Recovery times from this type of treatment are much shorter than traditional surgery; however, not all aneurysms can be treated this way. Your doctor can determine if you are a candidate for this treatment after performing your angiogram.

Part of the long-term treatment of a subarachnoid hemorrhage also involves addressing any risk factors that may have helped trigger the hemorrhage. This may mean quitting smoking if you're a smoker, gaining better control of your diabetes, lowering cholesterol and blood pressure, maintaining a healthy body weight, and eating a balanced diet.

Calling the doctor

The sooner the bleeding in the brain is controlled, the better the prognosis. It's important to seek emergency medical attention if you have any signs of a subarachnoid hemorrhage.


After a subarachnoid hemorrhage, serious complications can occur. Swelling in the brain, or hydrocephalus, is one of the potential complications. This is caused by the accumulation of cerebrospinal fluid and blood between the brain and skull, which can increase the pressure on the brain. Subarachnoid hemorrhage can also irritate and damage the brain's other blood vessels, causing them to tighten—this reduces blood flow to the brain. As blood flow becomes affected, another stroke can result, leading to even further brain damage. In serious cases, the bleeding may cause permanent brain damage, paralysis, or coma.  

Key points to remember

An excruciating headache—or the worst headache of your life—can be a sign of a potentially deadly, ruptured cerebral aneurysm and subarachnoid hemorrhage. Know the hallmarks of a subarachnoid hemorrhage, and seek immediate medical treatment if any of these symptoms affect you or a loved one.