Because of the rupture or blockage, a part of the brain is deprived of the blood it needs to function. The nerve cells in the affected area then can't function and will die in minutes. The devastating effects of stroke are often permanent because dead brain cells aren't replaced. They are caused by clots that plug an artery. Cerebral and subarachnoid hemorrhages are caused by ruptured blood vessels, and these have a higher fatality rate than strokes caused by clots.
Cerebral thrombosis is the most common type of stroke.
It occurs when a blood clot or thrombus forms and blocks blood flow in an artery bringing blood to the brain. This occurs more often in arteries damaged by atherosclerosis, a major risk factor for persons with diabetes. One identifying feature of cerebral thrombotic strokes is that they occur at night or first thing in the morning, when blood pressure is low. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood. The most common cause of these emboli is blood clots that form during arterial fibrillation.