Pathophysiology and treatment of subarachnoid hemorrhage.

The pathophysiology and treatment of acute subarachnoid hemorrhage (SAH) are reviewed. SAH occurs when blood is released into the subarachnoid space, which surrounds the brain and spinal cord. Symptoms of SAH include severe headache, nausea, vomiting, neck pain, nuchal rigidity, and photophobia. The initial hemorrhage is fatal in 20-30% of patients. Complications of SAH include rebleeding, hydrocephalus, delayed cerebral ischemia associated with cerebral vasospasm, and seizures. The likelihood of rebleeding is increased by measures that rapidly lower intracranial pressure. The risk of developing hydrocephalus is associated with the volume of blood within the subarachnoid space and ventricular system. Cerebral vasospasm develops in 20-40% of patients, and up to 50% of affected patients die or suffer permanent neurological damage. Seizures occur in 5-15% of patients with SAH. Radiologic procedures form the foundation for the diagnosis of SAH. The most commonly used rating scale classifies the severity of SAH based on the clinical presentation of the patient. Surgery is the definitive treatment for the prevention of rebleeding. Hydrocephalus can only be treated surgically, most commonly by insertion of a drain. The only measures proved to be effective for treatment of delayed cerebral ischemia are volume expansion and the induction of hypertension. The calcium-channel blocker nimodipine was recently approved for treatment of arterial spasm in SAH. Intravenous nicardipine is also being studied for the same indication. These agents may improve clinical outcome substantially by limiting fixed neurological deficits. To prevent seizures, prophylactic antiepileptic therapy with phenytoin sodium is generally accepted. The SAH complications of rebleeding, hydrocephalus, delayed cerebral ischemia, and seizures are managed by surgical, drug, and fluid therapy.