Stroke (or cerebrovascular accident or CVA) is the clinical designation for a rapidly developing loss of brain function due to an interruption in the blood supply to all or part of the brain. This phenomenon can be caused by thrombosis, embolism, or hemorrhage (AE) haemorrhage (BE).
Stroke is a medical emergency and can cause permanent neurological damage or even death if not promptly diagnosed and treated. It is the third leading cause of death and the leading cause of adult disability in the United States and industrialized European nations.
The symptoms of stroke can be quite heterogeneous, and patients with the same cause of stroke can have widely differing handicaps. Conversely, patients with the same clinical handicap can in fact have different underlying causes.
The cause of stroke is an interruption in the blood supply, with a resulting depletion of oxygen and glucose in the affected area. This immediately reduces or abolishes neuronal function, and also initiates an ischemic cascade which causes neurons to die or be seriously damaged, further impairing brain function.
Risk factors for stroke include advanced age, hypertension (high blood pressure), previous stroke or TIA (transient ischaemic attack), diabetes mellitus, high cholesterol, cigarette smoking, atrial fibrillation, migraine with aura, and thrombophilia. In clinical practice blood pressure is the most important modifiable risk factor of stroke, however many other risk factors, such as cigarette smoking cessation and treatment of atrial fibrillation with anticoagulant drugs, are important.
The traditional definition of stroke, devised by the World Health Organisation in the 1970s, is of a 'neurological deficit of cerebrovascular cause that persists beyond 24 hours or is interrupted by death within 24 hours'. This definition was largely devised for the purpose of research and the time frame of 24 hours appears purely arbitarily chosen as a cut-off point. It divides stroke from TIA (or 'mini-stroke'), which is the same as above but completely resolves clinically within 24 hours. The division of stroke and TIA into separate clinical entities is considered impractical and even unhelpful in practice by many stroke doctors. The main reason for this is the fact that stroke and TIA are caused by the same disease process, and both persons with a stroke or a TIA are at a higher risk of a subsequent stroke.
In recognition of this, and improved methods for the treatment of stroke, the term "brain attack" is being promoted in the Western World as a substitute for stroke or TIA. The new term makes an analogy with "heart attack" (myocardial infarction), because in both conditions, an interruption of blood supply causes death of tissue that is highly time dependent ('time is brain') and potentially life-threatening. Many hospitals have "brain attack" teams within their neurology departments specifically for swift treatment of stroke.