The Types of Stroke
The American Stroke Association (ASA), a division of the American Heart Association, reports that strokes happen almost every 40 seconds in the United States. The effects of stroke vary from person to person based on the type, severity, location, and number of strokes. Although there is no cure once it has occurred, advanced medical and surgical treatments are now available, giving many stroke victims hope for optimal recovery and reducing the risk of suffering another.
The Main Types of Stroke
An Ischemic stroke occurs when a blood vessel that supplies oxygenated blood to the brain becomes blocked or “clogged” and impairs blood flow to part of the brain. The brain cells and tissues begin to die within minutes from lack of oxygen and nutrients. The area of tissue death is called an infarct. 87% of strokes fall into this category. Ischemic strokes are further divided into 2 groups.
- Thrombotic strokes are caused by a thrombus (blood clot) that develops in the arteries supplying blood to the brain. This type of stroke is usually seen in older persons, especially those with high cholesterol levels and atherosclerosis (a buildup of fat and lipids inside the walls of blood vessels) or diabetes.
- Embolic strokes are usually caused by an embolus (a blood clot that forms elsewhere in the body and travels through the bloodstream to the brain). Embolic strokes often result from heart disease or heart surgery and occur rapidly and without any warning signs. About 15% of embolic strokes occur in people with atrial fibrillation, a type of abnormal heart rhythm in which the upper chambers of the heart do not beat effectively.
Hemorrhagic strokes occur when a blood vessel that supplies oxygenated blood to the brain ruptures and bleeds. When bleeding occurs in the brain, brain cells and tissues do not receive oxygen and nutrients. In addition, pressure builds up in surrounding tissues and irritation and swelling occur, which can lead to further brain damage. About 13% of strokes are caused by hemorrhage (10% are intracerebral hemorrhage and 3% are subarachnoid hemorrhage strokes). Hemorrhagic strokes are divided into 2 main categories.
- Intracerebral hemorrhage is usually caused by hypertension (high blood pressure), and bleeding occurs suddenly and rapidly. There are usually no warning signs and bleeding can be severe enough to cause coma or death.
- Subarachnoid hemorrhage results when bleeding occurs between the brain and the meninges (the membrane that covers the brain) in the subarachnoid space. This type of hemorrhage is often due to an aneurysm or an arteriovenous malformation (AVM).
The Signs of Stroke
Stroke symptoms may be sudden and if left untreated may result in death. Treatment is most effective when started immediately, so think FAST!
The Effects of Stroke in Different Areas of the Brain
The cerebrum is the part of the brain that occupies the top and front portions of the skull. It controls movement and sensation, speech, thinking, reasoning, memory, vision, and emotions. The cerebrum is divided into the right and left sides, or hemispheres. Depending on the area and side of the cerebrum affected by the stroke, any, or all, of these functions may be impaired.
- Right Hemisphere – Effects of a right hemisphere stroke may include: left-sided weakness or paralysis and sensory impairment, denial of paralysis, visual problems, spatial problems with depth perception or direction, inability to localize or recognize body parts, inability to understand maps and find objects, memory problems, behavioral changes and more.
- Left Hemisphere – Effects of a left hemisphere stroke may include: right-sided weakness, sensory impairment, problems with speech, visual problems, impaired ability to do math or organize, behavioral changes, impaired ability to read, memory problems and more.
The Cerebellum is located beneath and behind the cerebrum towards the back of the skull. It receives information from the body through the spinal cord. It helps coordinate muscle action and control, fine movement, coordination, and balance. Although strokes are less likely in the cerebellum area, the effects can be severe. Common effects of strokes in the cerebellum are: the inability to walk and problems with coordination and balance, dizziness, headache, nausea and vomiting.
The brainstem is located at the base of the brain right above the spinal cord. Many of the body’s vital “life-support” functions, such as heartbeat, blood pressure, and breathing, are controlled by the brainstem. It also helps control the main nerves involved with eye movement, hearing, speech, chewing, and swallowing. Unfortunately, death is a possibility with brainstem strokes.
If someone is exhibiting the signs of stroke, call 911 and get him or her to the nearest CHI St. Luke’s Health emergency department. Our Comprehensive Stroke Centers at Baylor St. Luke’s Medical Center and CHI St. Luke’s Health–The Woodlands Hospital meet the highest standards for treating even the most complex stroke cases.