A subarachnoid hemorrhage is a life threatening form of stroke where bleeding occurs between the outer layer of the brain and the inner layer of the skull. It is usually the result of a burst cerebral aneurysm, but can happen as the result of a head trauma.
A subarachnoid hemorrhage is a medical emergency requiring immediate treatment. However, it is still somewhat of a zebra and the emergency room must do a thorough, but quick, differential diagnosis to rule out more prosaic conditions (such as migraine). If subarachnoid hemorrhage can still not be ruled out, a CT scan will reveal the presence of bleeding in about 95% of cases. Even in the case of a negative result, a lumbar puncture should still be performed as this will show a hemorrhage in another 3% of cases. However, in the remaining cases, neither test will confirm the condition.
Once a subarachnoid hemorrhage is confirmed, immediate surgery is indicated. Current treatment involves the use of an angiogram to pinpoint the bleeding, and the use of a Guglielmi Detachable Coil inserted through a catheter to stem the bleeding.