Bradykinesia: gradual loss of spontaneous movement.
Corpus striatum: a part of the brain that helps regulate motor activities.
Cryothalamotomy: a surgical procedure in which a supercooled probe is inserted into a part of the brain called the thalamus in order to stop tremors.
Dementia: loss of intellectual abilities.
Dopamine: a chemical messenger, deficient in the brains of Parkinson's disease patients, that transmits impulses from one nerve cell to another.
Dyskinesias: abnormal involuntary movements that can result from long-term use of levodopa.
Festination: a symptom characterized by small, quick forward steps.
On-off effect: a change in the patient's condition, with sometimes rapid fluctuations between uncontrolled movements and normal movement, usually occurring after long-term use of levodopa and probably caused by changes in the ability to respond to this drug.
Pallidotomy: a surgical procedure in which a part of the brain called the globus pallidus is lesioned in order to improve symptoms of tremor, rigidity, and bradykinesia.
Parkinsonism: a term referring to a group of conditions that are characterized by four typical symptoms—tremor, rigidity, postural instability, and bradykinesia.
Postural instability: impaired balance and coordination, often causing patients to lean forward or backward and to fall easily.
Retropulsion: the tendency to step backwards if bumped from the front or upon initiating walking, usually seen in patients who tend to lean backwards because of problems with balance.
Rigidity: a symptom of the disease in which muscles feel stiff and display resistance to movement even when another person tries to move the affected part of the body, such as an arm.
Substantia nigra: movement-control center in the brain where loss of dopamine-producing nerve cells triggers the symptoms of Parkinson's disease; substantia nigra means "black substance," so called because the cells in this area are dark.
Tremor: shakiness or trembling, often in a hand, which in Parkinson's disease is usually most apparent wh en the affected part is at rest.
Wearing-off effect: the tendency, following long-term levodopa treatment, for each dose of the drug to be effective for shorter and shorter periods.