What causes a stroke?
The causes of stroke are many and various. Every individual is different and therefore no one stroke is ever the same as another. The ischemic stroke is usually caused by atherosclerosis (hardening) of blood vessels, embolus (a piece of blood clot originating from atherosclerotic plaque or heart) or small artery disease (the occlusion of small cerebral vessels).
Thrombosis is the formation of a blood clot (or thrombus). Atherosclerosis (hardening of the blood vessels as a result of the build up of fatty contents and cholesterol plaques on the vessel wall) causes blood vessels to narrow and restrict blood flow, which can lead to formation of a blood clot. If a blood clot develops in a blood vessel that supplies blood to the brain, the oxygen supply to the brain can be diminished or completely blocked leading to an ischemic stroke.
An embolism is a dislodged blood clot that has traveled through the blood vessels and it becomes wedged in an artery. In about 15% of all strokes, the emboli are blood clots that originally formed in the heart as a result of a rhythm disorder known as atrial fibrillation -- a rapid, irregular beat in the upper chambers of the heart (the atria). Because of the irregular pumping, some blood may pool in the heart chamber and form a clot, which can then break off and travel to the brain as an emboli, causing an ischemic stroke.
A hemorrhagic stroke occurs when there is a sudden bleed in the brain. A hemorrhagic stroke is usually the result of high blood pressure combined with arteriosclerosis (hardening of the blood vessels due to the build up of fatty contents and cholesterol plaques on the vessel wall), resulting in too much pressure on the blood vessel walls.
A cerebral hemorrhage occurs when a faulty blood vessel in the brain bursts, flooding the nearby areas of the brain. The most common sites are the basal ganglia (an area in the brain responsible for controlling voluntary movements and establishing postures), the cerebellum (an area in the brain that provides coordination of finely executed complex movements, including speech) the thalamus (an area in the brain that is the center of pain, touch, and temperature) and the pons (an area in the brain that acts as a relay station for messages in the brain and is important centers for regulating breathing).
A subarachnoid hemorrhage occurs when a blood vessel in the brain bursts, causing sudden bleeding into the space between the middle lining of the brain (the arachnoid membrane) and the brain itself. A subarachnoid hemorrhage causes sudden, severe pain in the head.