A stroke, also called “brain attack” or “cerebral vascular accident” occurs when brain cells die from oxygen deprivation.
Oxygen deprivation occurs if blood flow to the brain is blocked by a clot or if vessels are damaged. Without oxygen, brain cells cannot function.
There are two types of stroke: hemorrhagic and ischemic.
A hemorrhagic stroke occurs when a blood vessel in the brain bursts, due to high blood pressure, atherosclerosis, or a congenital malformation.
A burst vessel causes bleeding into the brain and decreased blood flow in the damaged vessel. Blood build-up increases pressure in the brain, damaging nerve cells and collapsing smaller vessels.
The second type of stroke is ischemic stroke, which occurs when blood flow through a vessel is blocked. There are three categories of ischemic stroke: thrombotic, thromboembolic, and embolic.
A thrombotic stroke occurs when flow in a blood vessel in the brain is obstructed by arteriosclerosis.
A thromboembolic stroke occurs when a clot breaks off from an arteriosclerotic plaque, and lodges in a downstream vessel, blocking blood flow.
An embolitic stroke occurs when a clot travels to the brain from elsewhere in the body. Patients with atrial fibrillation or who have suffered a heart attack are at high risk of embolic stroke. This is because slow, irregular, or interrupted blood flow has a tendency to clot.
Sometimes an individual will experience a transient ischemic attack (TIA), which is temporary and improves before cells die. A TIA is a precursor to a thrombotic stroke or short-term embolus.