What is a Stroke

Stroke occurs when a clogged or burst artery interrupts blood flow to the brain. This interruption of blood flow deprives the brain of needed oxygen and causes the affected brain cells to die. When brain cells die, function of the body parts they control is impaired or lost.

What are the types of stroke?

Stroke can be caused either by a clot obstructing the flow of blood to the brain (ischemic stroke) or by a blood vessel rupturing and preventing blood flow to the brain (hemorrhagic stroke).

Ischemic Stroke (Clots)

Ischemic stroke accounts for about 87 percent of all cases. Ischemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis.

These fatty deposits can cause two types of obstruction:

• Cerebral thrombosis refers to a thrombus (blood clot) that develops at the clogged part of the vessel.
• Cerebral embolism refers generally to a blood clot that forms at another location in the circulatory system, usually the heart and large arteries of the upper chest and neck. A portion of the blood clot breaks loose, enters the bloodstream and travels through the brain’s blood vessels until it reaches vessels too small to let it pass. A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation. It creates conditions where clots can form in the heart, dislodge and travel to the brain.

Hemorrhagic (Bleeds)

Hemorrhagic stroke accounts for about 13 percent of stroke cases. It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue. The two types of hemorrhagic strokes are intracerebral hemorrhage or subarachnoid hemorrhage.

• Intracerebral refers to blood escaping from blood vessels into deep tissue.
• Subarachnoid refers to blood escaping from blood vessels on the surface of the brain into the limited area called the subarachnoid space.

The two types of weakened blood vessels that may cause hemorrhagic stroke are aneurysms and arteriovenous malformations (AVMs).

• Aneurysm is a ballooning of a weakened region of a blood vessel. If left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain.
• Arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels. Any one of these vessels can rupture, also causing bleeding into the brain.