A stroke involves brain damage caused by a loss of blood circulation to an area of the brain. The blockage usually occurs when a clot or (less often) piece of atherosclerotic plaque breaks away from an artery elsewhere in the body and lodges within the vasculature of the brain.
Reviewed last on: 9/16/2008
Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.