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Subarachnoid Hemorrhage


The Manual's Editorial Staff

Last full review/revision Oct 2019| Content last modified Oct 2019
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What is a subarachnoid hemorrhage?

"Sub" means under. The arachnoid is a layer of tissue that covers your brain. Hemorrhage is bleeding. So a subarachnoid hemorrhage is bleeding under the arachnoid tissue layer. It's a medical emergency that can be fatal or cause long-lasting brain damage.

  • Subarachnoid hemorrhage happens when a blood vessel in your brain bursts

  • You get a sudden, severe headache and you may pass out

  • Doctors may do surgery to try to stop the bleeding

People who have any symptom of a subarachnoid hemorrhage should go to an emergency department immediately.

Bursts and Breaks: Causes of Hemorrhagic Stroke

When blood vessels of the brain are weak, abnormal, or under unusual pressure, a hemorrhagic stroke can occur. In hemorrhagic strokes, bleeding may occur within the brain, as an intracerebral hemorrhage. Or bleeding may occur between the inner and middle layer of tissue covering the brain (in the subarachnoid space), as a subarachnoid hemorrhage.

Bursts and Breaks: Causes of Hemorrhagic Stroke

What causes a subarachnoid hemorrhage?

A subarachnoid hemorrhage can be caused by a head injury (for example, from a car crash).

A subarachnoid hemorrhage not caused by injury is usually caused by an aneurysm bursting in your brain.

Aneurysms are bulges in a weakened area of a blood vessel's wall. Usually, you're born with these aneurysms. Sometimes aneurysms develop later from having high blood pressure for many years. You may have more than one aneurysm in your brain.

What are the symptoms of a subarachnoid hemorrhage?

When an aneurysm ruptures it usually causes:

  • Sudden, severe headache (sometimes called a thunderclap headache)

  • Passing out

  • Confusion

Almost half of people with a subarachnoid hemorrhage die before getting to a hospital. Some people remain in a coma or unconscious. People who wake up may be confused and sleepy and have:

  • A stiff neck

  • Vomiting and dizziness

  • Seizures

You may recover completely or be left with brain damage.

Later on, if you have more than one aneurysm, those aneurysms can burst too, giving you another hemorrhage.

How will my doctor know if I had a subarachnoid hemorrhage?

Doctors will usually suspect subarachnoid hemorrhage based on your symptoms. To make sure they're right, they'll do tests right away to see if your brain is bleeding and where it's bleeding:

  • Sometimes angiography to get detailed pictures of the blood vessels inside your brain

  • Sometimes, a spinal tap (when doctors take some fluid with a long, thin needle from your spine to check for blood)

How do doctors treat a subarachnoid hemorrhage?

Doctors will treat the problems that cause your bleeding. They'll have you stay in a hospital or stroke center where you may get:

  • Bed rest with no activity

  • Medicine to relieve your headache and prevent an ischemic stroke (no aspirin or ibuprofen as these can cause more bleeding)

  • Medicine and fluids to keep your blood pressure at the right level

  • Sometimes, doctors put a small metal coil in the leaking aneurysm or do surgery to close it

  • If you have more than one aneurysm, doctors will usually treat those too, so they don't bleed later

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