Because subarachnoid hemorrhage is life-threatening, anyone experiencing the onset of a massive, sudden, crushing headache that has never been experienced like this before should go to a hospital emergency room (if there are no other accompanying symptoms). If there are additional symptoms, the emergency physician should be called for help.
In the further course, the attending physician tries to determine the temporal development of the complaints, the exact course of which an accompanying person can give further information about. This is especially the case if the patient is confused or dazed. The family history is then taken in order to establish whether strokes and cerebral haemorrhages have occurred in the family before, as a frequent occurrence within the family is not uncommon.
Imaging techniques are used to diagnose SAB. A computed tomography (CT) scan usually reveals the subarachnoid hemorrhage as a flat, white area adjacent to the surface of the brain. While almost every SAB is detected by CT within the first 12 hours after hemorrhage, CT still detects 93% of the SAB present after 24 hours. For this reason, CT is considered the most reliable examination method in the acute phase after a subarachnoid hemorrhage. If 7 days have already passed since the onset of the SAB, a pathological change is only detected in every second CT finding.
In some cases, such as in extremely anaemic patients, SAB can only be detected by MRI or lumbar puncture. In response to the bleeding, the affected vessels may spasm (vasospasm), causing further paralysis in some affected individuals. These vasospasms can only be detected with the help of a special ultrasound examination of the brain vessels (transcranial Doppler sonography).
In order to determine the source of the bleeding (aneurysm), the doctor performs an X-ray imaging of the vessels (angiography), which is still considered the best method, although simpler examinations are now available (magnetic resonance angiography, CT angiography).