A subarachnoid hemorrhage occurs when the blood vessels in the brain hemorrhage into the subarachnoid space, the space between the brain and the thin membrane that covers it. Subarachnoid hemorrhages are often caused by trauma, that is, someone hitting their head in an accident or fall. The rupture of a cerebral aneurysm is also a common cause of this type of brain hemorrhage, especially in persons aged 20-60 who are smokers and/or who have high blood pressure.
An aneurysm is an area of a blood vessel wall that has been injured or worn thin, due to increased pressure, disease, or atherosclerotic plaque rupture. This thin vessel wall is weak and can dissect or balloon and rupture, hemorrhaging into the surrounding tissues.
Other causes of subarachnoid hemorrhage include: bleeding disorders, congenital abnormalities (such as an arteriovenous malformation), a use of blood thinners, and without known cause (idiopathic). The symptoms of this form of cerebral hemorrhage include sudden loss of consciousness, sudden light sensitivity, loss of feeling or movement in the limbs, seizure, nausea and vomiting, stiff neck and muscle aches, and confusion or sudden mood shift.
According to the Brain Aneurysm Foundation, nearly half of all people die within minutes of a massive brain hemorrhage. Of those 50 percent who survive, half will still succumb. The remaining 25 percent often suffer long-term disability and loss of function. Vasospasm, leading to stroke, is one potential complication that increases the severity of the condition.
A subarachnoid hemorrhage causes damage to the brain, and many times death, by limiting blood flow to the brain tissues, potentially causing infarcts (areas of dead tissue from a lack of oxygen); putting pressure on the brain as a pocket of blood between it and the skull; causing edema and brain swelling, which then exerts even more pressure on the brain; and by blocking the circulation of the cerebrospinal fluid, which then causes further brain swelling in the ventricles of the brain, the interior chambers that make cerebrospinal fluid.
The recovery of a patient who has suffered a subarachnoid hemorrhage depends on the cause of the hemorrhage, with aneurysm survivors having a longer recovery time than non-aneurysm hemorrhage patients. Comatose patients also have a longer recovery ahead of them due to the severity of the hemorrhage.
When dealing with brain hemorrhages, location and severity are key factors in survival, recovery, and treatment. The underlying cause is also a factor for recovery and preventing future hemorrhages. Hypertension is one of the leading causes of brain hemorrhage, accounting for 80% of cerebral hemorrhage patients. Brain hemorrhages can be avoided by treating high blood pressure when it is diagnosed, refraining from smoking and drugs, seeking follow up care for blood thinner prescriptions (such as Coumadin), and being aware of the options for known vessel abnormalities. However, these precautions are not always successful, as approximately 40,000 people in the United States have spontaneous brain hemorrhages each year.