Subarachnoid Hemorrhage

Medically Reviewed by Christopher Melinosky, MD on August 24, 2022
Written by Diana Reese
4 min read

A subarachnoid hemorrhage is a type of bleeding stroke that happens between your brain and the membrane that surrounds it. (This area is called the “subarachnoid” space; “hemorrhage” means bleeding.) It can happen when an artery is damaged and starts to bleed.

Like any other stroke, a subarachnoid hemorrhage is an emergency. Call 911 right away if you suspect you or anyone close to you has had one. It may feel like the worst headache you’ve ever had. Symptoms may also include:

Don’t delay -- call 911 right away.

A subarachnoid hemorrhage happens most often when there’s a bulge, or aneurysm, in an artery wall near the surface of the brain. Other causes include:

  • Bleeding from an arteriovenous malformation (AVM), an abnormal tangle of blood vessels in the brain
  • Other blood vessel issues

Risk factors

It’s not possible to prevent all subarachnoid hemorrhages. But if aneurysms run in your immediate family, tell your doctor. You may need to get tested to find out if you have a brain aneurysm that hasn’t ruptured. These things also raise your risk for a subarachnoid hemorrhage:

They’re also slightly more common in women.

You may get one or more of these imaging tests to see if there’s bleeding in your brain:

CT scan. Computed tomography uses a series of X-rays combined by a computer to form an image that’s more detailed than a single X-ray. A CT scan doesn’t always show a small subarachnoid hemorrhage or one that happened a week or more ago.

MRI. Magnetic resonance imaging uses a large magnet and radio waves to create images of your brain. You might get a contrast dye by IV to enhance the images. It can reveal bleeding that’s happened in the recent past.

Other tests that can help with diagnosis include:

  • Cerebral angiogram. You’ll have a catheter (a thin, flexible tube) placed into an artery in your leg and threaded up to your brain. Then you’ll get a contrast dye by IV to highlight the blood vessels in your brain on X-rays.
  • Spinal tap. Also called a lumbar puncture, a health care worker will put a needle into your back to collect spinal fluid to check for blood.

You may need to repeat imaging tests, such as the CT scan, because bleeding doesn’t always show up right away.

If you have a subarachnoid hemorrhage, you’ll be hospitalized right away, preferably at a center that treats strokes.

At the hospital, you may get medications to ease your headache and to help prevent seizures and clot-related (“ischemic”) strokes that can happen when an artery has narrowed. Doctors will try to keep your blood pressure high enough to keep blood flowing in your brain but low enough to stop excessive bleeding. If you have too much fluid in the brain, doctors may need to put in an external ventricular drain. This thin, flexible tube drains the extra fluid and prevents pressure on the brain.

If you have an aneurysm that has burst, you may get one of the following procedures to stop or prevent further bleeding:

  • Endovascular coiling. Using the catheter in a cerebral angiogram, your doctor will put a tiny coiled wire into the aneurysm, where it forms a clot that stops the bleeding.
  • Endovascular stent. Instead of a coil, you’ll get a tiny tube called a stent placed across the aneurysm. The stent channels the blood away from the aneurysm to prevent it from leaking or bursting.
  • Clip. Your doctor will make a surgical cut (incision) in your scalp and remove a piece of your skull to reach the aneurysm. A special microscope will help your doctor find the aneurysm and fasten a tiny clip across it, replace the piece of skull, and sew up the surgical cut.

A subarachnoid hemorrhage can have serious short- and long-term effects. One potentially fatal problem is that a brain aneurysm will bleed again. This can happen shortly after the first episode of bleeding. Other early problems include vasospasm and hydrocephalus. Vasospasm happens when a blood vessel narrows and cuts off oxygen to your brain. Hydrocephalus is a buildup of fluid on the brain.

Long-term complications can include seizures and problems with memory and thinking, as well as depression, anxiety, and posttraumatic stress disorder (PTSD).