artery and aneurysm | Cleveland Clinic
An aneurysm forms when there is a weakness between the layers of the artery. Shown is a normal artery and its three layers. An aneurysm can form either as a ballooning on one side of the artery or as a dilatation (enlargement) of the entire artery at a segment.

What is subarachnoid hemorrhage (SAH)?

Subarachnoid hemorrhage (SAH) is a type of stroke. Head trauma is the most common cause.

In patients without head trauma, SAH is most commonly caused by a brain aneurysm. A brain aneurysm is a ballooning of an artery in the brain that can rupture and bleed into the space between the brain and the skull.

Risk factors for developing an aneurysm include:

What are the symptoms of subarachnoid hemorrhage (SAH)?

Most subarachnoid hemorrhages caused by brain aneurysms do not cause symptoms until they rupture. A ruptured brain aneurysm is an emergency and 9-1-1 should be called immediately. Symptoms of a ruptured brain aneurysm include:

  • Sudden worst headache of life
  • Associated neck or back pain
  • Nausea and vomiting
  • Decreased responsiveness
  • Sudden weakness
  • Dizziness
  • Seizure

Last reviewed by a Cleveland Clinic medical professional on 06/18/2018.

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