An ischemic stroke is caused when the arteries in the brain are blocked or narrowed to the point at which the brain's blood flow, and thus its oxygen, is cut off, according to Mayo Clinic. Most strokes are ischemic strokes.
There are two types of ischemic strokes, says Mayo Clinic. The first is the thrombotic stroke, in which a blood clot forms and is lodged in an artery that serves the brain. The clot might not be made of blood but of a fatty deposit called an atheroma, says Cedar Sinai. In the embolic stroke, the clot is formed away from the brain and travels from its point of origin, usually the heart, until it is caught in an artery too small for it to pass through. This is a risk for people who have had recent heart surgery.
A person who experiences symptoms of a stroke needs to seek medical attention right away, says Mayo Clinic. He should not wait until the symptoms subside. Symptoms include numbness or paralysis on one side of the body, including the face. The person also has trouble speaking and seeing with both eyes and may be stricken with a headache that is very sudden and severe. This might lead to dizziness, vomiting or a change in consciousness.