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Subarachnoid Hemorrhage

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Written by Tim Becker, MD.
Resident Physician, The Mount Sinai Hospital
Last updated January 5, 2021

Subarachnoid hemorrhage quiz

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A subarachnoid hemorrhage is characterized by a leakage of blood into the space between the first and second membranes surrounding the brain.

What is a subarachnoid hemorrhage?

A subarachnoid hemorrhage is characterized by a leakage of blood into the space between the first and second membranes surrounding the brain. The accumulation of blood causes the pressure inside the skull to increase, which can lead to brain damage and death.

Symptoms include a sudden and severe headache, known as a thunderclap headache. Vision changes, pain behind your eyes, a stiff neck, dizziness, nausea and vomiting, seizures, and a change in consciousness may also result. In cases indicating brain damage, you may also experience difficulty speaking, unilateral weakness, difficulty walking, and coma.

Treatments include medication, procedures to prevent further bleeding, and possible physical therapy as a means of recovery.

Call 911 immediately. This condition is a medical emergency requiring immediate attention.

Symptoms of a subarachnoid hemorrhage

The primary symptom of SAH is sudden, severe headache, as well as a few other related symptoms. Some stroke-like symptoms may occur, indicating that brain damage has occurred.

Severe headache

This headache, also called a thunderclap headache, will be sudden and severe. It can be described as:

  • Unique: It often feels different from other headaches you've had before, and people often consider it the "worst headache of their life."
  • Self-resolving: If you experience only a small leak of blood, this headache may resolve on its own, but this can be a warning sign of a larger hemorrhage (a sentinel headache).

Other symptoms

A few other symptoms stemming from the headache may include:

  • Vision changes: You may find yourself sensitive to bright light or experience blurry or double vision.
  • Orbital pain: You may feel pain or pressure in the space behind your eyes.
  • Seizures: This is defined as uncontrollable shaking or stiffness.
  • Confusion: You may become disoriented to where you are or other basic facts.
  • Passing out
  • Stiff neck
  • Dizziness
  • Nausea
  • Vomiting

Further symptoms indicating brain damage

If the SAH leads to brain damage, you can develop typical stroke symptoms, depending on what parts of the brain were damaged. These can include:

  • Difficulty speaking
  • Weakness or numbness of one side of the body
  • Difficulty walking
  • Coma

What causes a subarachnoid hemorrhage

The brain is surrounded by three membranes (meninges). The space between and first (pia) and second membrane (arachnoid) is called the subarachnoid space. Thus, blood leaking into this area is called a subarachnoid hemorrhage. Causes include a ruptured cerebral aneurysm, arteriovenous malformation, head trauma, and rare causes like vasculitis and brain tumors.

Ruptured cerebral aneurysm

This is by far the most common cause of SAH. An aneurysm forms when a portion of a blood vessel becomes thin and "balloons out" with blood. This usually occurs where two vessels connect, at the base of the brain. When the aneurysm becomes unstable, the vessel can leak or spill blood (hemorrhage) into the space between two membranes that cover the brain (subarachnoid space).

Aneurysms usually develop over a period of time, typically after age 40, and do not cause symptoms until they rupture. It is not known exactly why aneurysms develop. Some factors that can contribute to aneurysm formation include:

  • Smoking
  • High blood pressure (hypertension)
  • Excessive alcohol consumption
  • A family history of aneurysms
  • Autosomal dominant polycystic kidney disease (PKD): This is a rare kidney disease that runs in families.

Arteriovenous malformation (AVM)

AVM is a less common cause of SAH. Arteries normally carry blood at a high pressure and connect to veins, which carry blood at lower pressures through webs of tiny vessels (capillaries).

AVM and SAH occur when:

  • Arteries connect abnormally: During early development in the womb, arteries and veins can sometimes accidentally connect to each other in abnormal ways.
  • The veins stretch and weaken: The high-pressure arterial blood is connected directly to the veins, causing the veins to stretch and become weak.
  • Blood vessels later leak: If these vessels leak blood around the brain, it will result in SAH.

Head trauma

Severe head injuries can also damage blood vessels and cause them to leak contents into the subarachnoid space, regardless of whether an underlying aneurysm existed. These are referred to as "traumatic subarachnoid hemorrhages."

Rare causes

The following rarer causes can also result in SAH.

  • Vasculitis: Blood vessels can become inflamed due to infection or the body attacking healthy tissue (such as with an autoimmune condition).
  • Brain tumors: An abnormal growth of cells in and around the brain can disrupt normal blood vessels and lead to bleeding.


After bleeding occurs, residual blood surrounding the brain can irritate arteries and cause them to become narrower (vasospasm). This can reduce blood flow to brain cells and result in additional brain damage. The effects from vasospasm may be greater than the original hemorrhage. This usually occurs within three to eight days after the initial hemorrhage, but can be treated [4].

Treatment options and prevention

Depending on the severity of your SAH, it can be remedied by medication, various procedures, or physical therapy. There are a few different ways to help prevent SAH from occurring.


Blood surrounding the brain can irritate arteries and cause them to narrow, leading to further brain damage (see vasospasm above). Calcium channel blockers, more typically used for high blood pressure, can be used to prevent these arteries from narrowing, in order to prevent further brain damage.


If your SAH was due to abnormal blood vessels, procedures can correct these abnormalities to prevent repeat bleeding.

  • Endovascular coiling: A physician can insert a thin tube (a catheter) into your blood vessels and guide it to the site of an aneurysm. The tube can be used to place a small metal coil into the vessel at the site of the aneurysm. This reduces the blood flow into the aneurysm, causing it to balloon less and making it less likely to rupture again.
  • Aneurysm clipping: During brain surgery, a surgeon can put a small metal clip at the base of an aneurysm, separating it from the larger blood vessel so that it cannot bleed again.
  • AVM alleviation: AVMs can be alleviated through radiation, surgery, or embolization. During embolization, a special chemical is injected into the AVM to cut off its blood supply.

Physical therapy

If the SAH results in neurologic damage, such as weakness or difficulty speaking, then therapists can help you learn exercises to regain as much physical and mental strength and speaking function as possible.


Unfortunately, most people do not know they have an aneurysm or AVM until a bleed occurs. Most people with aneurysms never experience symptoms. If you have multiple relatives who have had bleeding, you can ask your physician to discuss risks and benefits of screening for aneurysms, which can sometimes be corrected with preventive procedures.

Lifestyle modifications may also help reduce risk of SAH by reducing wear-and-tear on blood vessels and preventing high blood pressure. These include:

  • Avoiding smoking
  • Avoiding cocaine use
  • Moderating alcohol consumption
  • Eating a healthy diet
  • Exercising regularly
  • Maintaining a healthy weight

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When to seek further consultation

You should seek further consultation any time you experience a particularly severe headache or any related changes to your behavior or overall wellness.

If you have a sudden "worst headache of your life" that gets better

If you have a sudden and very severe headache, you should discuss this with your physician. It could be a sign of a small bleed (sentinel headache) and your physician may be able to help you avoid a larger bleed.

If you have a severe headache with nausea and vomiting

Call 911 or have someone take you to the nearest emergency room if you experience a sudden and very severe headache with nausea, as this may be a sign of SAH, which, if untreated, can result in severe brain damage or death.

If you experience seizures

After the SAH, five percent of people can develop epilepsy, a disorder of repeated seizures [8]. Seizures can take several forms, including loss of consciousness, stiffness, and shaking, and can last a few seconds to several minutes. If you experience a seizure, it is important to report this to your physician, who can provide medications to prevent further seizures.

If you experience changes in your thinking or emotions

After the SAH, it is common to experience difficulties with memory or attention. Your physician can help you access occupational therapy services or further support to help you learn to compensate for these problems. It is also common to experience depression or anxiety, which can be alleviated with medications and psychotherapy.

Questions your doctor may ask to diagnose

  • How long has your current headache been going on?
  • Are you sick enough to consider going to the emergency room right now?
  • How severe is your headache?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Any fever today or during the last week?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Hear what 1 other is saying
Once your story receives approval from our editors, it will exist on Buoy as a helpful resource for others who may experience something similar.
The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Somebody watching over me.Posted April 25, 2024 by T.
My heels occurred in 1998. I was at my office and after a meeting in my office I stood up and I had a sharp pain running up the back of my neck and ran all the way to the front of my head.. It felt as if someone park a car in my head. I started to see double and the pain was so sever that I had to vomit. The pain subsided a little after about 15 minutes. I decided to drive home and rest. Don't do this. I had God watching after me on this drive home. I began forgetting things about work so I decided to go the the Hospital Emergency room. I was lucky there was no one in the ER at the time and by the time I got there I could not speak my name. They did a CT scan and found the brain bleed. I live in the Philadelphia area and we have allot of university hospital. My sister in law is a nurse and her friend knew of a Dr Rosenwasser at Jefferson hospital and correcting brain bezels was all his team did an Endovascular coilin. At the time the procedure was relatively new in the US but I was a great candidate for this experimental procedure. I was lucky and had no side effects as a result of the bleed. I learned that after you sever headache don't go to sleep to try to sleep it off call 911 and get to the hospital right away. The aneurysm could beels a second time and the results could be sever. I am fortunate to have survived and now they have so many treatments options for you.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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  2. What You Should Know About Subarachnoid Hemorrhages. Johns Hopkins Medicine Health Library. Johns Hopkins Medicine Link
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  9. Recovery. Brain Aneurysm Foundation. BAF Link