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Subarachnoid Hemorrhage

  1. What is a subarachnoid hemorrhage?
  2. Symptoms
  3. Causes
  4. Diagnosis
  5. Treatment
  6. Complications
  7. Recovery
  8. FAQs
  9. Other names for subarachnoid hemorrhage

What is a subarachnoid hemorrhage?

Subarachnoid hemorrhage (SAH) is a type of stroke in which there is bleeding on the surface of brain. The bleeding occurs in a space between the layers of tissues that cover the brain, in an area called the subarachnoid space. SAH is a medical emergency and is life-threatening. People who survive an SAH may be left with disability.

SAH is normally due to a weakness of the vessel walls, which results in a balloon-like swelling known as an aneurysm. A hemorrhage occurs when the aneurysm bursts due to the pressure of blood as it is pumped through the brain.

The most common symptom is a sudden, severe headache, often with nausea and vomiting and sometimes loss of consciousness.[1]

The diagnosis is confirmed either by doing a CT (computed tomography) scan of the head or by taking a sample of the fluid from around the spinal cord and testing it for the presence of blood.

Treatment depends upon the severity and may include emergency life-saving measures, surgical repair of the bleeding area and medications to reduce the risk of complications.

The outlook after a subarachnoid hemorrhage depends on the size and severity of the bleed.

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Subarachnoid hemorrhage signs and symptoms

The most common symptom is a sudden, explosive headache called a thunderclap headache, which is often described as the worst headache ever or as if there had been a blow to the head. It may last only a few seconds or even a fraction of a second.[2]

There is often a phase of intense headache for days or weeks before the bleed, which may often go unnoticed by doctors as an early warning sign of subarachnoid hemorrhage. If you or someone you know is experiencing a headache, try the Ada app for a free symptom assessment.

Good to know: If a person experiences a sudden, severe headache, medical advice should be sought immediately.

Read more about Headaches »

Other symptoms may include:[3][4]

  • Nausea and vomiting
  • Dizziness
  • A stiff neck
  • Blurred or double vision
  • Eyes which are sensitive to light
  • Drowsiness
  • Slurred speech
  • Weakness on one side of the body
  • Confusion
  • Convulsions, i.e. uncontrollable shaking
  • Loss of consciousness

Subarachnoid hemorrhage causes

Subarachnoid bleeding is bleeding in the head which occurs in the subarachnoid space, the space between the layers of tissue that cover the brain. This can cause pressure on the brain and problems supplying the brain with blood.

It is commonly due to the rupture of a saccular aneurysm, also known as a berry aneurysm: a small, berry-like swelling that forms within the brain due to a weak spot in an artery wall. Occasionally, there may be another cause for subarachnoid bleeding, such as in traumatic subarachnoid hemorrhage, when a head or neck trauma may cause blood to leak into the subarachnoid space from nearby structures.[2]

Subarachnoid hemorrhage risk factors

This condition is not common. It tends to be more common in middle-aged adults, although it can affect people of any age.

Risk factors which most commonly lead to SAH include:[2][5]

  • High blood pressure
  • High alcohol use
  • Smoking
  • Cocaine use

Risk factors that lead to SAH less commonly, include:[2][6]

  • Head and neck trauma, when bleeding from injury to the brain or other nearby structures leaks into the subarachnoid space, which is known as traumatic subarachnoid hemorrhage
  • Certain inherited conditions that weaken the blood vessels, such as autosomal dominant polycystic kidney disease (ADPKD), Marfan-Syndrome and Ehlers-Danlos syndrome.
  • Vasculitis, when blood vessels inside the brain become swollen and inflamed due to infection or to conditions affecting the immune system.
  • Brain infection such as encephalitis

Subarachnoid hemorrhage diagnosis

Anyone displaying any signs of stroke should immediately be taken to a hospital emergency room for diagnosis. Typically, this will first involve a physical examination and a review of the person’s medical history, before a number of other scans and tests:[4][7][8]

Brain scans

Brain scans help confirm diagnosis. A scan can also help to show the severity and location of the bleed and any problems it may be causing.

Brain scans should be carried out as quickly as possible after the person reaches the hospital, allowing for prompt and appropriate treatment to be received.

Subarachnoid hemorrhage CT scan

A CT (computed tomography) scan of the head is, in general, the best method to detect bleeding. Additionally, it is quicker and more widely available than an MRI scan. For more information, see the resource on CT scans (Head) . A computed tomography angiogram (CTA scan) may be included with a CT scan. This is a type of CT involving an injection of dye into a vein, which highlights blood vessels and can identify the location of the bleeding.

For information, see the resource on CT Angiograms.

Subarachnoid hemorrhage MRI scan

A magnetic resonance imaging (MRI) scan uses radio waves and a strong magnetic field to build a detailed image of the interior of the body.

A magnetic resonance angiogram (MRA) scan may be included with an MRI scan. This is a procedure that shows the blood vessels of the brain so doctors can identify the location of the bleeding, often without the need for injecting a contrast agent. If a contrast agent is used, it will involve an injection of dye into a vein using a peripheral intravenous line, usually placed in the veins of the arms or hands.

Subarachnoid hemorrhage lumbar puncture

If the diagnosis is still uncertain, a sample of fluid from around the spinal cord will be taken and investigated for blood.

The brain and the spinal cord are surrounded by a clear liquid called cerebrospinal fluid (CSF). The cerebrospinal fluid will contain blood if there has been an SAH.

A lumbar puncture involves taking a sample of the CSF by inserting a needle between two vertebrae ‒ bones of the spine ‒ at the lower end of the spine known as the lumbar region. A small amount of this fluid is drawn off in a syringe and examined in a laboratory, where diagnosis may be confirmed.

Subarachnoid hemorrhage treatment

A subarachnoid hemorrhage is a medical emergency and requires urgent review and treatment.

The aim of treatment for subarachnoid hemorrhage is to stabilize the affected person, prevent bleeding or re-bleeding from the aneurysms and prevent further brain injury.[2]

Subarachnoid hemorrhage lifesaving measures

Life-saving measures, such as help with breathing and blood pressure, may be needed in the time directly following the bleed, especially if the bleed is big enough to cause a large increase in the pressure inside the head. Pain relief is usually given to treat the headache.[9]

Subarachnoid hemorrhage medication

Some medications are given in the short-term. These may include:[1][9]

  • Nimodipine to improve the blood supply to the brain, which can become dangerously low after an SAH
  • Blood pressure medication to prevent rebleeding
  • Pain relief
  • Anticonvulsants to prevent seizures
  • Antiemetics to stop the affected person feeling sick and vomiting

Subarachnoid hemorrhage surgery

Surgery might be needed to treat SAH. This aims to treat the aneurysm that was responsible for the SAH, as well as any other aneurysms that may be present. The risk of rebleeding is high initially after an SAH, so these procedures are done as soon as possible, usually within 72 hours.

Some complications may require different surgical approaches, such as to lower the pressure inside the skull or to remove clotted blood.

There are two main surgeries that may be given to block off blood flow from the aneurysm:[7][10]

Subarachnoid hemorrhage coiling

Coiling is usually done under general anesthesia. A flexible tube, known as a catheter, is inserted into an artery in the leg or groin and passed along the blood vessels in the body until it reaches the aneurysm in the brain.

The aneurysm is blocked from the inside by inserting small platinum coils via the arteries that run from the groin into the brain. This prevents further bleeding by causing blood to clot around the coils, sealing off the weakened area.

Subarachnoid hemorrhage clipping

Less commonly, clipping may be used to stop or prevent an aneurysm from bleeding. A clipping procedure is done under general anesthesia and involves opening the skull in a procedure known as a craniotomy.

During clipping, a neurosurgeon places a tiny clip across the neck of the aneurysm to block the blood flow from entering the aneurysm.

Coiling versus clipping

The procedure chosen is often dependent on factors such as the location, size and shape of the aneurysm.

Coiling is often preferred because it aims to be minimally invasive, as it does not involve opening the skull and has a lower risk of short-term complications than clipping, such as seizures.

Coiling tends to lead to a shorter hospital stay and a shorter recovery time, though these factors are generally more dependent on the rupture’s severity than the type of surgery used.

However, since coiling is a relatively new procedure, the long-term benefits over clipping are uncertain.

Subarachnoid hemorrhage complications

A number of complications can arise in the days and weeks after a person has experienced an SAH, either while they are still in hospital or once they are at home or in a rehabilitation facility. These complications are important to recognize and treat in a timely manner, as they can, in some cases, lead to serious health problems and may be life-threatening.

Some of the most common complications include:[1][11]

Subarachnoid hemorrhage rebleeding

Particularly in the few days after the SAH, the aneurysm is at risk of bursting again; this is known as rebleeding.

Repair of the aneurysm should be done as soon as possible, generally within 72 hours, to avoid this, as it can lead to permanent disability or may be life threatening.

Subarachnoid hemorrhage vasospasm

Also known as delayed cerebral ischemia, vasospasm is a common complication of an SAH. If it occurs, it is usually between the fourth and fourteenth day after the initial SAH.

This is when a blood vessel goes into spasm, causing the vessel to narrow, and the blood supply to the brain is dangerously low. The brain relies on a constant supply of blood to provide it with oxygen and nutrients. When the supply of blood becomes blocked, brain cells can quickly begin to stop working. If the blockage lasts for more than a couple of minutes, these cells can die, leading to serious damage to the brain. Depending on the location and supply area of the affected vessel, the damage can range from mildly debilitating to severe or life-threatening.

Common symptoms of vasospasm include:

  • Drowsiness
  • Stroke-like symptoms, such as weakness down one side of the body or speech problems

Treatments such as Nimodipine are available to prevent and treat vasospasm.

Hydrocephalus after subarachnoid hemorrhage

Subarachnoid hemorrhage can commonly lead to disruption of the production and drainage of cerebrospinal fluid (CSF), which can lead to a buildup of fluid on the brain, known as hydrocephalus. This increases pressure on the brain, which can lead to brain damage.

Hydrocephalus may be treated with an external ventricular drain, which allows the temporary drainage of cerebrospinal fluid (CSF) from the ventricles of the brain, relieving raised intracranial pressure.


Seizures may develop after an SAH, usually starting within the first year after the hemorrhage.

Common symptoms of seizures include:[12]

  • Loss of consciousness
  • Muscle twitching and jerking
  • Becoming stiff

Cognitive dysfunction after subarachnoid hemorrhage

This is when a person experiences problems with one or more brain functions and affects most people, who have experienced an SAH, to some degree.

Some common thinking problems include:[13]

  • Memory problems, usually with remembering new information rather than with information from before the hemorrhage
  • Difficulty concentrating for longer periods of time, often on previously straightforward tasks, such as making a cup of tea, and being easily distracted

Emotional difficulties after subarachnoid hemorrhage

After SAH, many people experience emotional problems, feel fearful of living with future complications or illness recurrence and may feel a loss of confidence in everyday tasks or social activities.

These problems may include:[11][14]

Emotional difficulties generally improve with time, and there are various treatments available to help, including:

  • Talking therapies, such as psychotherapy
  • Medications, such as antidepressants
  • Support groups to speak to others who have had similar experiences

Speech difficulties

Some people may find that their speech becomes slurred or slowed, or that they have difficulty finding the right words to express themselves. This usually improves gradually. A language therapist may be able to advise on management of cases of significant speech difficulties.

Physical disabilities after subarachnoid hemorrhage

Sometimes, a person may experience weakness of one or more limbs. This generally improves over several months, though it will initially be hard to predict the level of recovery possible.

Subarachnoid hemorrhage recovery

The time it takes to recover from a subarachnoid hemorrhage depends on its severity. Recovery takes a minimum of three weeks. For many, it may be several months, and some symptoms may be permanent. Three months is the average time until people feel able to return to previous activity levels, such as work.[11]

Associated problems, such as loss of feelings in the limbs or problems understanding speech are determined by the location of the hemorrhage.

Subarachnoid hemorrhage FAQs

Q: Subarachnoid hemorrhage vs subdural hematoma - what is the difference?
A: A subdural hematoma is another condition where blood collects on the surface of the brain in a layer of tissue between the arachnoid space and the skull. The two conditions have similar symptoms and may both cause brain damage. It is usually caused by a head injury, whereas a subarachnoid hemorrhage is usually caused by a weakness in the blood vessel walls.

Both a subarachnoid hemorrhage and a subdural hematoma cause a headache as their primary symptom. The subdural hematoma headache is a progressive headache, whereas the subarachnoid hemorrhage headache is known as a thunderclap headache, sudden in onset and severe from the beginning.[15]

Other names for subarachnoid hemorrhage

  • Bleeding in the brain
  • Subarachnoid haemorrhage (British English)
  • Aneurysmal subarachnoid hemorrhage
  • Rupture of an intracranial aneurysm
  • Ruptured cerebral aneurysm
  • Ruptured intracranial aneurysm

  1. AMBOSS. "Subarachnoid hemorrhage." Accessed 27 July 2018.

  2. Patient.info. "Subarachnoid Haemorrhage | Warning Signs." Accessed 31 July 2018.

  3. Patient. "Subarachnoid Haemorrhage. SAH information page." 14 January 2015. Accessed 27 July 2018.

  4. UptoDate. "Patient education: Stroke symptoms and diagnosis (Beyond the Basics)." 7 Jul. 2017. Accessed 27 July 2018.

  5. BMJ Best Practice. "Subarachnoid haemorrhage." Accessed 27 July 2018.

  6. American Journal of Roentgenology - AJR. "Subarachnoid Hemorrhage: Beyond Aneurysms." Accessed 27 July 2018.

  7. Brain & Spine Foundation. "Subarachnoid Haemorrhage." Accessed 31 July 2018.

  8. Medscape eMedicine. "Subarachnoid Hemorrhage." 13 October 2017. Accessed 31 July 2018.

  9. NHS.UK. "Subarachnoid haemorrhage - Treatment." Accessed 31 July 2018.

  10. Medscape. "Subarachnoid Hemorrhage Treatment & Management." 13 October 2017. Accessed 31 July 2018.

  11. Salford Royal NHS Foundation Trust. "Recovery Advice." Accessed 31 July 2018.

  12. NHS.UK. "Epilepsy." Accessed 30 July 2018.

  13. Salford Royal NHS Foundation Trust. "Recovery Advice.". Accessed 30 Jul. 2018.

  14. NHS.UK. "Subarachnoid haemorrhage - Complications." Accessed 30 July 2018.

  15. NHS.UK. "Subdural haematoma." Accessed 31 July 2018.