A stroke is the sudden death of brain cells due to lack of oxygen. A stroke is usually defined as one of two types:
- Ischemic (caused by a blockage in an artery)
- Hemorrhagic (caused by a tear in the artery's wall that produces bleeding into or around the brain)
The consequences of a stroke, the type of functions affected, and the severity, depend on where in the brain it has occurred and the extent of the damage.
Blood Flow Blockage. Strokes are caused by either blood flow blockage to the brain (ischemic stroke) or the sudden rupture of an artery in the brain (hemorrhagic stroke). Brain cells require a constant supply of oxygen to stay healthy and function properly. Therefore, blood needs to be supplied continuously to the brain through two main arterial systems:
- The carotid arteries come up through either side of the front of the neck. (To feel the pulse of a carotid artery, place your fingertips gently against either side of your neck, right under the jaw.)
- The basilar artery forms at the base of the skull from the vertebral arteries, which run up along the spine, join, and come up through the rear of the neck.
Blockage of blood flow to the brain for even a short period of time can be disastrous and cause brain damage or even death.
Review Date: 05/06/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.