When a person's supply of blood suddenly stops flowing to the brain, or if the flow diminishes severely, the event classifies as a stroke. MayoClinic.com states such a medical emergency requires immediate help. The organization states that the sooner the stroke victim gets help, the less brain damage will occur and the more chance the person can recover.
Embolic Stroke
This form of stroke occurs when the blood clot forms outside of the arteries leading to the brain, but tries to pass through larger arteries. When the clot reaches the brain, it may become caught in the brain because the arteries there are narrow. This kind of clot, MayoClinic.com states, typically forms in the heart do to an irregular heartbeat--called an arrhythmia--in both the heart's top chambers, a condition named atrial fibrillation. The embolic stroke is classified as an ischemic stroke as well.
Thrombotic Stroke
When a clot of blood blocks the arteries that go to the brain, the condition is classified as a thrombotic stroke. The blood clot, called thrombus, can form because of plaques in the arteries. These may build up because of high cholesterol, especially the fatty portions of cholesterol, called triglycerides. It also may occur because of cardiovascular disease. The blockage may not block the entire flow, so the thrombotic stroke falls under the category of ischemic stroke, MayoClinic.com reports.
Subarachnoid Hemorrhage
Hemorrhagic strokes occur because of bleeding in the brain not caused by a clot. Subarachnoid hemorrhaging begins when bleeding occurs in an artery at the brain's surface, MayoClinic.com reports. This causes blood to spill into the area between the skull and the brain. This causes a severe headache that begins with a sensation similar to a thunderclap. This particular side effect commonly means a bleeding event has begun. An aneurysm occurs when a portion of the wall of an artery weakens, usually because of heart disease. This weakened pocket in the artery wall can rupture, causing the bleed. This type of stroke may cause more problems because of a condition called vasospasm that makes blood vessels relax and constrict abnormally, which decreases blood flow as well.
Intercerebral Hemorrhage
An intercerebral hemorrhage also is a bleed in the brain not caused by a clot, but rather by a blood vessel burst. MayoClinic.com reports that this sort of hemorrhagic stroke most frequently results from untreated high blood pressure. The force of blood through the tiny blood vessels of the brain--and throughout the body--can make these tubes weaken and break. The blood flows into the brain in abnormal ways, and the areas where blood should flow become starved for oxygen and damaged.
