Cerebral Cortex Suggested as Genesis of Tremors in Parkinson's Disease

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Parkinson's disease, first described nearly 200 years ago by a British physician for whom the disease is named (and who dubbed it the "shaking palsy"), is widely thought to show abnormalities in the basal parts of the brain - causing the characteristic tremors, stiffness of the limbs and poor balance.

Now new research led by John Caviness, M.D., Professor of Neurology at Mayo Clinic in Arizona, suggests that the cerebral cortex of the brain is also responsible for significant abnormal muscle activity in Parkinson's disease. The study results were published in the October 2005 edition of Movement Disorders Journal.

Parkinson's disease, part of a group of conditions known as motor system disorders, is characterized by tremor of the hands and arms, as well as stiffness of the limbs and slowness of movement.

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Nearly 50,000 Americans generally over age 50 are affected by the progressive disease each year, and medical science has struggled to pinpoint exact causes in the vast majority of cases.

The basal portion of the human brain is thought to regulate movement in a place called basal ganglia. It has long been thought that the abnormal basal ganglia in Parkinson's disease patients produce the movement problems. The cerebral cortex, the outermost layer of the brain considered the most complex portion, is also involved in voluntary movement execution and regulates planning, problem-solving, language and speech.

In the study, Dr. Caviness - along with authors from Barrows Neurological Institute, Phoenix, and Sun Health Research Institute, Sun City, Ariz., - examined the significance of postural tremors in patients with Parkinson's. Postural tremor, as opposed to "rest" tremor in Parkinson's, is observed when a patient attempts to "hold" or "posture" against gravity - such as holding one's arms out in front.

Patients who participated in this study were fitted with electrodes over the scalp to measure electrical discharge patterns from the cerebral cortex. The goal was to study the role of the cerebral cortex in the generation of postural tremors. The authors found that the electrical activity of brain cells from the cerebral cortex creates abnormal muscle activity. These abnormal rhythms create tremor and may create other problems in Parkinson's disease.

What is the significance of this finding? "Understanding the role of the abnormalities in the cerebral cortex in Parkinson's will help design new treatments that help problems which arise partially or entirely from the cerebral cortex," says Dr. Caviness.

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