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Carotid and vertebral arteries

How is a subarachnoid hemorrhage (SAH) diagnosed?

  • Computerized tomography (CT scan) of the brain is a simple, effective way to see a subarachnoid hemorrhage. Another type of CT scan, CT angiography (CTA), visualizes blood vessels using contrast material injected intravenously (through a vein). Sometimes, a CT scan may miss a very small subarachnoid hemorrhage, or one that has occurred a week or two ago. Other tests may be ordered to detect a subarachnoid hemorrhage if a CT scan is negative. These tests include:
  • Lumbar puncture. A small needle is placed in the lowest part of the back to obtain cerebrospinal fluid, the fluid that bathes our brain and spinal cord. The fluid is tested for subarachnoid hemorrhage.
  • Magnetic resonance imaging (MRI) of the brain. This imaging test can show if there has been “subacute” blood, or bleeding in the brain, in the recent past.

Other tests given after subarachnoid hemorrhage (SAH) is diagnosed

The hospital care following the diagnosis of subarachnoid hemorrhage focuses on both discovering and treating the cause of the SAH, as well as managing its complications.

Aneurysm detection

Since brain aneurysms cause over 80 percent of nontraumatic subarachnoid hemorrhages, it is very important to image the brain’s arteries and then treat the aneurysm.

The most common test performed to best see the brain’s blood vessels is a cerebral angiogram. A catheter is placed in the main artery in the groin (femoral artery) or wrist (radial artery). Through this a thinner catheter is advanced through the body’s arterial system into the neck. Contrast material is then injected and the X-ray pictures capture the blood flowing in the brain’s arteries and brains.

Occasionally, subarachnoid hemorrhages may be caused by other brain or spine vascular lesions. An MRI of the brain and/or spine may be ordered if a cerebral angiogram does not demonstrate a brain aneurysm.

A much rarer vascular cause for subarachnoid hemorrhage, benign perimesencephalic SAH is a type of SAH in which no vascular lesion is found on imaging. Some theories regarding cause include bleeding from a vein or from a blood clot in the blood vessel wall.

Preventing aneurysm rebleeding

Once an aneurysm has ruptured, there is an increased chance that it can rebleed. Brain aneurysm rebleeding is dangerous and can be fatal. The chance of rebleeding can be reduced by:

  • Securing the aneurysm
  • Controlling blood pressure
  • Correcting any bleeding disorder or reversing certain types of blood thinning medications.

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

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