Overview

A subarachnoid hemorrhage is bleeding in the space between your brain and the surrounding membrane (subarachnoid space). The primary symptom is a sudden, severe headache. The headache is sometimes associated with nausea, vomiting and a brief loss of consciousness.

Bleeding usually results from the rupture of an abnormal bulge in a blood vessel (aneurysm) in your brain. Sometimes bleeding is caused by trauma, an abnormal tangle of blood vessels in your brain (arteriovenous malformation), or other blood vessel or health problems.

Untreated, a subarachnoid hemorrhage can lead to permanent brain damage or death.

Diagnosis

To diagnose a subarachnoid hemorrhage, your doctor is likely to recommend:

• CT scan. This imaging test can detect bleeding in your brain.Your doctor may inject a contrast dye to view your blood vessels in greater detail (CT angiogram).
• MRI. This imaging test also can detect bleeding in your brain. Your doctor might inject a dye into a blood vessel to view the arteries and veins in greater detail (MR angiogram) and to highlight blood flow.
• Cerebral angiography. You doctor inserts a long, thin tube (catheter) into an artery in your leg and threads it to your brain. Dye is injected into the blood vessels of your brain to make them visible under X-ray imaging. Your doctor might recommend cerebral angiography to obtain more-detailed images or if a subarachnoid hemorrhage is suspected but the cause isn't clear or doesn't appear on other imaging.

Up to 22 percent of aneurysmal subarachnoid hemorrhages don't appear on initial imaging tests. If your initial tests don't show bleeding, your doctor might recommend:

• Lumbar puncture. Your doctor inserts a needle into your lower back to withdraw a small amount of fluid that surrounds your brain and spinal cord (cerebrospinal fluid). The fluid is examined for the presence of blood, which can indicate a subarachnoid hemorrhage.
• Repeated imaging. The tests might be repeated several days after the initial testing.

Source: http://www.mayoclinic.com