If the intracranial pressure becomes great enough, portions of the brain may be forced outward through skull openings, such as the foramen magnum at the base of the skull. Approximately 20 percent of strokes are called hemorrhages, during which a blood vessel ruptures and bleeding occurs into or around the brain. The other 80 percent of strokes are due to infarctions. In this situation, a blood vessel becomes blocked and blood can not reach an area of the brain. The area of the brain that does not receive adequate blood dies because of a lack of oxygen and other vital nutrients.
Brain infarction is quite similar to an infarction in the heart, or heart attack.
The brain is the most sophisticated computer ever created. Just as a computer can lose part of its programs due to a faulty chip or circuit, the brain too can lose functionality from stroke-induced damage. Because the brain controls the electronic circuits that make up the nervous system, damage to it presents problems such as loss of language, paralysis, loss of vision, poor balance and sensory loss. Clinical findings vary greatly depending on the location and extent of brain damage done by a stroke. A very severe stroke may even cause a loss of consciousness.