Syncope. A neurologist's viewpoint.

Syncope is caused by a global reversible reduction of blood flow to the brain. Three hemodynamic abnormalities can cause syncope: (1) a fall in systemic blood pressure because of ineffective control of peripheral vascular resistance, (2) an acute decrease in cardiac output, and (3) an acute increase in cerebrovascular resistance. Complicating the differential diagnosis of syncope are other causes of loss of consciousness, such as seizures, metabolic disorders, and psychiatric disorders, which may simulate syncope.