Subarachnoid hemorrhage is a type of stroke that occurs when there is bleeding in the subarachnoid space, which is the area between the brain and the tissue that covers it. This type of stroke is typically caused by the rupture of a cerebral aneurysm, a bulging blood vessel in the brain. Subarachnoid hemorrhage is a medical emergency and can lead to serious complications, including brain damage and death. Research in this area focuses on improving early detection and treatment methods for subarachnoid hemorrhage, as well as understanding the underlying causes and risk factors for this condition.