Parkinson's Disease Health Center

Glossary of Parkinson's Disease Terms

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Thalamus: A large group of brain cells centrally placed deep in the brain near its base and serving as a major relay station for impulses traveling from the spinal cord and cerebellum to the cerebral cortex.

Toxin: A poisonous substance.

Tremor: Rhythmic shaking and involuntary movement of part(s) of the body due to muscle contractions.

Unilateral: Occurring on one side of the body. Parkinson's disease symptoms usually begin unilaterally.

Wearing-off effect: The tendency, following long-term levodopa treatment, for each dose of the drug to be effective for shorter periods of time.