Whole brain showing Sub arachnoid hemorrhage

A subarachnoid hemorrhage (SAH) is a life-threatening medical emergency caused by bleeding into the subarachnoid space, an area between the brain and the tissues covering it, most often from a ruptured brain aneurysm or head trauma. Key symptoms include a sudden, severe "thunderclap" headache, stiff neck, nausea and vomiting. Diagnosis involves imaging like a CT scan and sometimes a spinal tap along with treatment focusing on stopping the bleeding and preventing complications.