A stroke occurs when an artery is blocked or ruptured, reducing the supply of blood and oxygen to a part of the brain. The longer brain cells go without oxygen, the more likely they are to die and result in disability. The dying cells set off a chain reaction of electrical and chemical changes that can further damage that area of the brain.
A brain attack is the early phase -- first few hours -- of a stroke, when doctors and researchers can attempt to correct the effects that can lead to disability.
A stroke describes the period after the first few hours when doctors can't alter the damaging effects in physiology that lead to permanent disability.
Ischemic strokes are caused when a blood clot or plaque clogs an artery. These types of strokes account for 85% of all strokes and usually cause symptoms on one side of the body without pain.
Strokes that are caused by blockages in the carotid arteries (circulation to the brain) can be due to atherosclerosis or hardening of the arteries. Cholesterol-filled white blood cells accumulate in the artery wall. The lining of the artery becomes rough from the plaque causing the artery's passageway to narrow. A clot or piece of plaque may break loose from the artery lining and travel upstream with the blood flow. This process will eventually cut off the blood supply to that part of the brain causing an ischemic stroke.
When smaller clots of plaque break away and attach to a small artery a mini-stroke or Transient Ischemic Attack (TIA) occurs. The attack may last less than 30 seconds or result in small episodes throughout the day. A person may experience weakness or dizziness and be unable to talk, see or move a part of the body. Once the episode is over the person recovers as though nothing has happened. This is a warning sign for an upcoming major stroke and needs to be fully evaluated at your nearest hospital.
Hemorrhagic stroke occurs when a blood vessel ruptures in or near the brain. This type of stroke may be caused by the effects of severe or long-standing high blood pressure or by an aneurysm - a weak spot on the artery wall that balloons out to form a blood-filled pouch. Aneurysms and vascular malformations are the most common causes of acute subarachnoid hemorrhage and are curable if treated early. If left untreated they are life-threatening.
Call 911 if you experience any of these warning signs.
"Patients with a hemorrhagic stroke usually have a sudden onset of symptoms that worsen rapidly. Most patients describe this sudden onset as the worst headache of their life," says Dr. Aldrich.