Subarachnoid hemorrhage

Diagnosis of subarachnoid hemorrhage

The first test is a CT scan

If subarachnoid hemorrhage is suspected on the basis of symptoms, a CT scan is performed. As blood mixes with the cerebrospinal fluid when subarachnoid hemorrhage occurs, CT shows a specific pattern of test results. If CT does not reveal any hemorrhage because the amount of hemorrhage is too small or the time since onset is too long, MRI is performed. If MRI does not reveal any obvious hemorrhage, cerebrospinal fluid is sampled by inserting a syringe into the back to confirm whether any blood is present.

[ A CT showing subarachonid hemorrhage ]

A yellow arrow indicates subarachonid hemorrhage

Once subarachnoid hemorrhage has been diagnosed, the next step is to investigate the location of the broken vessel (which is a cerebral aneurysm in many cases). Cerebral angiography via catheterization is the most accurate test. MRA, which investigates the state of blood vessels using MRI, and contrast-enhanced CT, in which CT is carried out after administration of a contrast agent, may also reveal the cerebral aneurysm, but may not be able to provide detailed information, including its shape.

[ Radiological studies for cerebral aneurysms ]

Yellow arrows indicate a cerebral aneurysm.

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