Stroke Information

Introduction

A stroke is the sudden death of brain cells due to lack of oxygen. A stroke is usually defined as one of two types:

• Ischemic (caused by a blockage in an artery)
• Hemorrhagic (caused by a tear in the artery's wall that produces bleeding into or around the brain)

The consequences of a stroke, the type of functions affected, and the severity, depend on where in the brain it has occurred and the extent of the damage.

Blood Flow Blockage. Strokes are caused by either blood flow blockage to the brain (ischemic stroke) or the sudden rupture of an artery in the brain (hemorrhagic stroke). Brain cells require a constant supply of oxygen to stay healthy and function properly. Therefore, blood needs to be supplied continuously to the brain through two main arterial systems:

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• The carotid arteries come up through either side of the front of the neck. (To feel the pulse of a carotid artery, place your fingertips gently against either side of your neck, right under the jaw.)
• The basilar artery forms at the base of the skull from the vertebral arteries, which run up along the spine, join, and come up through the rear of the neck.

Blockage of blood flow to the brain for even a short period of time can be disastrous and cause brain damage or even death.

Click the icon to see an image of the brain.

Ischemic Stroke

Ischemic strokes are by far the more common type, causing nearly 90% of all strokes. Ischemia means the deficiency of oxygen in vital tissues. Ischemic strokes are caused by blood clots that are usually one of three types:

• Thrombotic stroke
• Embolic stroke
• Lacunar stroke

Thrombotic or Large-Artery Stroke and Atherosclerosis. The thrombotic stroke accounts for about 60% of all strokes. It usually occurs when an artery to the brain is blocked by a thrombus (blood clot) that forms as the result of atherosclerosis (commonly known as hardening of the arteries). These strokes are also sometimes referred to as large-artery strokes. The process leading to thrombotic stroke is complex and occurs over time: