A stroke (syn: cerebrovascular accident, CVA), is a medical condition whereby the blood supply to the brain is interrupted. This is due to either a blood clot or vessel narrowing preventing blood flow, or a hemorrhage. The interruption of blood flow causes ischemia of the cerebral tissues (brain cell death), commonly leading to a sensory or motor deficit lasting longer than 24 hours (a deficit lasting less than 24 hours is termed a Transient Ischemic Attack). The severity of disability is dependent on the site and extent of ischemia. In western countries, stroke is the most common cause of permanent disability, and a leading cause of death.
The risk of stroke increases with age. Smoking, hypertension (high blood pressure), excess alcohol intake, as well as other medical conditions such as atrial fibrillation and other heart conditions, diabetes and high cholesterol are also important preventable risk factors. There is also an increased risk associated with taking estrogen-containing medications (such as the combined oral contraceptive pill and HRT), due to thickening of the blood.