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Subarachnoid Hemorrhage

  1. What is a subarachnoid hemorrhage?
  2. Risks
  3. Symptoms
  4. Diagnosis
  5. Treatment
  6. Prevention
  7. Other names for subarachnoid hemorrhage

What is a subarachnoid hemorrhage?

Subarachnoid hemorrhage is a condition where there is bleeding in the head. The bleeding occurs in a space between the layers of tissues that cover the brain, in an area called the subarachnoid space. It is commonly due to a burst blood vessel in the brain, due to weakness of the vessel walls or a malformation. The most common symptom is a sudden, severe headache, often with nausea and vomiting. The diagnosis is confirmed either by doing a 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 bleed and medications to reduce the risk of complications. The outlook after a subarachnoid hemorrhage depends on the size and severity of the bleed.


Subarachnoid bleeding is bleeding in the head which occurs in subarachnoid space (the space between the layers of tissues that cover the brain). This can cause pressure on the brain, and problems supplying the brain with blood. Causes include a burst blood vessel in the head (a ruptured aneurysm) and diseases which cause blood vessel damage, such as vasculitis or blood vessel malformations. Smoking and high blood pressure may also increase the risk of this condition. This condition is not common. It tends to be more common in middle-aged adults, although it can affect people of any age.


The most common symptom is a sudden, severe headache which is often described as 'the worst headache ever' or as if there had been a blow to the head. Other symptoms may include nausea and vomiting, dizziness, a stiff neck, blurred vision, eyes which are sensitive to light, drowsiness, a loss of consciousness and seizures.


The diagnosis may be suspected based on the symptoms and a physical exam of the affected person, but is usually confirmed by doing a CT (computed tomography) scan of the head, which shows the bleed. If the diagnosis is still uncertain, a sample of fluid from around the spinal cord will be taken (a lumbar puncture) and investigated for blood. Other tests may be done to confirm the diagnosis or look for the cause, including an MRI (magnetic resonance imaging) scan of the head and angiography (injecting dye into blood vessels and doing a scan to look at their size and structure).


A subarachnoid hemorrhage is a medical emergency and requires urgent review and treatment. 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 an large increase in the pressure inside the head. Pain relief is usually given to treat the headache. Some medications are given in the short-term to reduce the risk of a further bleed, to improve the blood supply to the brain and to treat any symptoms, such as seizures. Surgery might be needed to repair the cause or to remove large collections of blood.


Giving up smoking and getting good control of high blood pressure may help to prevent some episodes of subarachnoid hemorrhage.

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