Stroke, also called a brain attack, occurs when blood flow to a part of the brain is disrupted and oxygen cannot get to that part of the brain. Disruption in blood flow is caused when either a blood clot or piece of plaque blocks one of the vital blood vessels in the brain (ischemic stroke), or when a blood vessel in the brain bursts, spilling blood into surrounding tissues (hemorrhagic stroke). Ischemic strokes occur more frequently than hemorrhagic strokes.
The brain needs a constant supply of oxygen and nutrients in order to function. Even a brief interruption in blood supply can cause problems. Brain cells begin to die after just a few minutes without blood or oxygen, and never recover.
Due to both the physical and chemical changes that occur in the brain with stroke, damage can continue to happen over several days. This is called a stroke-in-evolution.
Brain cell death leads to the loss of function. This may include impaired ability with movement, speech, thinking and memory, bowel and bladder, eating, emotional control, and other vital body functions.
The specific abilities lost or affected depend on where in the brain the stroke occurs and on the size of the stroke (i.e., the extent of brain cell death). A small stroke may result in only minor problems such as weakness in an arm or leg. Larger strokes may cause paralysis (inability to move part of the body), loss of speech, or even death.
Transient Ischemic Attacks
If the blood clot goes away quickly on its own and the symptoms go away, this is called a Transient Ischemic Attack (TIA). TIAs may last up to 24 hours, but they often last only a few minutes. TIAs occur when the blood supply to part of the brain is briefly interrupted. TIA symptoms are similar to those of stroke, but do not last as long. Most symptoms of a TIA disappear within an hour. About one-third of strokes are preceded by one or more TIAs that can occur days, weeks or even months before a stroke.
Because TIAs are temporary and the body soon returns to normal, it is easy to ignore them or to believe that the problem has disappeared. However, it is dangerous to ignore TIAs, because the underlying problem that caused the TIA continues to exist. TIAs are often early warning signs of more serious and debilitating stroke in the future.