A subarachnoid hemorrhage (SAH) occurs when there is bleeding in the area between the brain and the surrounding tissue — known as the subarachnoid space. This space contains cerebrospinal fluid and serves to cushion the brain, protecting it from injury. An SAH most commonly occurs as a result of an aneurysm, when a weak area in a blood vessel bursts. The buildup of blood and pressure around the brain and skull can lead to brain cell damage, physical and mental disabilities, and even coma or death.
An SAH can occur quite suddenly and can often be the result of severe head trauma. A suspected SAH requires immediate medical intervention. Symptoms can include severe headache, nausea or vomiting, seizure and loss of consciousness. Physicians may use one or more of several tests to determine if a subarachnoid hemorrhage has taken place, including CT scans, MRIs and spinal taps to determine the presence of blood in the spinal fluid.
Subarachnoid hemorrhages are rarer than intracerebral hemorrhages, and recovery can be difficult, often taking months or even years. Approximately half of patients who survive an SAH will have neurological disabilities that may last the rest of their lives.