Strokes and the Brain

The brain is a complex organ. Each area of the brain is responsible for a particular function or ability. The brain is divided into four main parts: the right hemisphere (or half), the left hemisphere, the cerebellum and the brain stem.

A stroke in the right hemisphere of the brain often causes paralysis in the left side of the body. This is known as left hemiplegia. In addition, a stroke in this part of the brain may cause:

• Problems with spatial and perceptual abilities. For example, the stroke survivor may misjudge distances and fall, or be unable to guide her hands to pick up an object.

• Impaired judgment and behavior. For example, she may try to do things that she should not attempt to do, such as trying to drive a car.

• Problems with short-term memory. Although she may be able to recount events from 30 years ago, she may be unable to remember what she ate for breakfast that morning.

Someone who has had a left hemisphere stroke may have right hemiplegia, paralysis of the right side of the body. She may also have:

• Aphasia-speech and language problems.

• Slow and cautious behavior, in contrast to the behavior of a right-hemisphere stroke survivor. She may need a lot of help to complete tasks.

• Memory problems similar to those of right-hemisphere stroke survivors. For example, she may have trouble learning new information and have poor short-term memory.

A stroke that takes place in the cerebellum can cause:

• Abnormal reflexes of the head and torso

• Coordination and balance problems

• Dizziness, nausea and vomiting.

Strokes that occur in the brain stem are especially devastating. The brain stem is the area of the brain that controls all of our involuntary "life-support" functions, such as breathing rate, blood pressure and heartbeat. The brain stem also controls abilities such as eye movements, hearing, speech and swallowing. Since impulses generated in the brain's hemispheres must travel through the brain stem on their way to the arms and legs, patients with a brain stem stroke may also develop paralysis in one or both sides of the body.