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Subarachnoid Hemorrhage

What is a subarachnoid hemorrhage?

A subarachnoid hemorrhage means that there is bleeding in the space that surrounds the brain. Most often, it occurs when a weakened area in a blood vessel (aneurysm) on the surface of the brain bursts and leaks. The blood then builds up around the brain and inside the skull increasing pressure on the brain. This can cause brain cell damage, life-long complications, and disabilities.

When an 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. 

What causes a subarachnoid hemorrhage?

A subarachnoid hemorrhage may occur as a complication of a type of stroke called a hemorrhagic stroke, or bleeding inside the brain. This is different from an ischemic stroke, which is caused by a blood clot.

This bleeding can sometimes cut through the brain tissue and leak into the area outside the brain (called the subarachnoid space). This is called a subarachnoid hemorrhage and can be life-threatening. The blood from the hemorrhage can compress or displace vital brain tissue. A severe hemorrhage can cause a coma, or leave you paralyzed.

What are the symptoms of a subarachnoid hemorrhage?

Common symptoms of a subarachnoid hemorrhage 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

The symptoms of a subarachnoid hemorrhage may resemble other conditions or medical problems. Always consult your health care provider for a diagnosis.

A brain aneurysm (which can lead to a subarachnoid hemorrhage) can cause these symptoms:

  • 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

How is subarachnoid hemorrhage diagnosed?

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

  • MRI scan. This diagnostic procedure uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of the brain.
  • CT scan. This imaging procedure uses a combination of X-rays and computer technology to produce horizontal, or axial images (often called slices) of the brain. CT scans are more detailed than general X-rays.
  • Angiogram. During this test, dye is injected in the blood vessel and then X-rays are taken to evaluate blood flow through them.
  • Spinal tap. In this test, a special needed is placed into the lower back, into the spinal canal. The pressure in the spinal canal and brain can be measured. A small amount of  cerebrospinal fluid can be removed and analyzed for the presence of blood


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

How is a subarachnoid hemorrhage treated?

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. This procedure is done by either a radiologist or a neurosurgeon. It requires making a tiny incision in your groin and passing a thin tube called a catheter through the artery in your leg up to the artery in your head that is bleeding. Recovery time from this type of treatment is 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 doing an angiogram.

Part of the long-term treatment of a subarachnoid hemorrhage also involves addressing any risk factors that may have helped trigger the hemorrhage. The most significant risk factor is smoking. If you smoke, you need to quit. Gaining better control of contributing conditions such as diabetes, high cholesterol, or high blood pressure are also important Maintaining a healthy body weight, and eating a balanced diet can also reduce your risk.

What are the complications 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 build up 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. 

When should I call my health care provider?

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

  • Seizures
  • Severe headache; the worst headache pain that you have ever experienced
  • Nausea and vomiting with the headache
  • Double vision
  • Neck stiffness
  • Difficulty speaking
  • Drooping eyelid
  • Confusion and difficulty concentrating
  • Sensitivity of light with the headache

Key points

A subarachnoid hemorrhage means that there is bleeding in the space that surrounds the brain.

  • It is life threatening and a medical emergency.
  • It occurs in people over 40 years of age.
  • It usually presents as an excruciating headache—or the worst headache of your life.
  • It’s important to know the hallmarks of a subarachnoid hemorrhage.
  • Seek immediate medical treatment if any of the above symptoms occur affecting you or a loved one.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
Online Medical Reviewer: Petersen, Sheralee, MPAS, PA-C
Online Medical Reviewer: Weisbart, Ed, M.D.
Date Last Reviewed: 1/2/2014
© 2000-2015 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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