A stroke is what happens when the brain is damaged as the result of a problem with its blood supply. Each part of the brain is responsible for a particular function, so the symptoms that result will depend on which part of the brain is deprived of its blood supply.
By noting down exactly what the problems are and examining you, it is usually possible for the doctor to be reasonably accurate in identifying where the stroke is. Strokes can be large or small, depending on which artery and which part of it has been affected. The damage can occur in two major ways. The commonest, occurring in about 80% of cases, is where one of the arteries becomes blocked with a blood clot. This can be due to ‘furring up’ of the artery with cholesterol, which results in the lining of the artery becoming rough and allowing blood cells and platelets to stick to it. (Platelets are the fragments in the blood that stick together when necessary to form a blood clot.) Alternatively, a clot can be formed further downstream, then becoming dislodged and traveling up the artery until it reaches a point where the clot is bigger than the artery, where it becomes stuck. These clots can come from the heart or the aorta (the main artery from the heart) or from the carotid or vertebral arteries. The blockage causes the part of the brain supplied by that artery to be deprived of oxygen and nourishment, resulting in damage to the nerve cells. The remaining 20% of strokes are due to hemorrhage (bleeding) into the brain – intracerebral hemorrhage – or onto the surface of the brain – subarachnoid hemorrhage. Intracerebral hemorrhage can occur from any of the arteries in the brain, but most commonly affects small arteries deep inside the brain. A hemorrhage causes damage as a result of the escaped blood squashing the surrounding brain tissue.
What actually is a stroke?