A stroke is a sudden onset of a neurological deficit (loss of strength, control, or sensation) due to a problem with the blood supply in the brain.
The most common type of stroke is an ischemic stroke. Ischemic means that the brain does not get enough blood. Think of it like a hose watering your lawn during a drought. If the hose gets blocked for a long enough time, the lawn will burn up and die. If an artery supplying blood to the brain gets blocked by a blood clot, then the brain will "burn up and die" for lack of blood. Unlike the lawn, the brain can only go for a short time, at most about 3 hours, without blood before it burns up. Of course if the entire brain is not getting blood, it is only a matter of minutes before irreversible damage occurs. That is why if a person's heart stops, it is important to apply CPR or get it started again within minutes. Otherwise, the brain will become damaged.
The symptoms of an ischemic stroke, and the severity, depend on how large an artery is blocked and what part of the brain it supplies. Symptoms can be paralysis of one or more limbs, loss of sensation (numbness, tingling), loss of vision, loss of balance, or a number of other symptoms. The onset of the symptoms is sudden.
It is important to get the stroke patient to the emergency room immediately. This is because we now have "clot-buster" drugs that can dissolve the clot of they are given in the first 3 hours of a stroke. After 3 hours, it is too late, as the brain has been damaged irreparably. If you are present when a person demonstrates the sudden onset of the symptoms of a stroke, you should call 911 to have the person transported to the hospital.
A hemorrhagic stroke occurs when blood leaks into the brain from a flaw in a blood vessel. These strokes are also quite serious and patients with these must be treated in an ICU. High blood pressure is often a factor in causing these kinds of strokes. It requires trained specialists and equipment to determine which type of stroke a person has had. Since the treatment depends on the type of stroke, it is important that patients with stroke symptoms be transported to the hospital immediately.
Organizations
Washington University Internet Stroke Center
Support Groups