Health Library

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 weak 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 or vomiting
  • Severe headache — the worst headache pain you've ever had that feels different from other headaches
  • Trouble speaking
  • Drooping eyelid
  • Confusion and trouble concentrating
  • Sensitivity to light
  • Neck stiffness
  • Seizures

The symptoms of a subarachnoid hemorrhage may look like other conditions or medical problems. Always see your healthcare 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
  • Trouble 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 test uses large magnets, radiofrequency energy, and a computer to make detailed images of the brain.
  • CT scan. This test uses X-rays and computer technology to make 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 needle 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

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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. 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 do surgery to place a small clip on the blood vessel to stop blood from leaking into the brain.

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 involves addressing any risk factors that may have helped trigger the hemorrhage. One of the most significant risk factors 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 healthcare 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 had
  • Nausea and vomiting with the headache
  • Double vision
  • Neck stiffness
  • Trouble speaking
  • Drooping eyelid
  • Confusion and trouble concentrating
  • Sensitivity to light with the headache

Key points about subarachnoid hemorrhage

  • A subarachnoid hemorrhage means that there is bleeding in the space that surrounds the brain.
  • It is life threatening and a medical emergency.
  • It usually occurs in people over 40 years of age.
  • It usually presents as the worst headache of your life.
  • Seek immediate medical treatment if any of the above symptoms affect you or a loved one.

Next steps

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

  • Know the reason for your visit and what you want to happen.
  • 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 name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
  • Ask if your condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if you do not take the medicine or have the test or procedure.
  • 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.