One of the four cardinal symptoms of Parkinson’s disease and often the first symptom to cause a person to seek medical attention. The tremor of Parkinson’s is slow and steady, about four hertz; and generally is more prevalent at rest than with activity. Tremor indicates malfunction of neu-ronal circuits involving the thalamus, which filters nerve signals that enter and leave the cerebral cortex, the midbrain, the basal ganglia, or the cerebellum. In Parkinson’s, the imbalance of neurotransmItters in the basal ganglia permits erratic and chaotic communication among neurons. This effect overwhelms the thalamus, which passes on many of these signals to the cerebral cortex, where they become messages of action to the muscles.
Tremors generally improve with anti-parkinson’s MEDICATIONS such as ANTICHOLINERGIC MEDICATIONS, which suppress acetylcholine, the neurotransmitter that conveys nerve signals to the muscles, and with dopaminergic medications, which supplement or restore brain dopamine levels and restore the brain’s neurotransmitter balance. levodopa, the standard dopaminergic therapy, creates a nonendogenous source the brain can use to synthesize additional dopamine; the dopamine agonists act like artificial dopamine in the brain, directly stimulating dopamine receptors.
Tremors are not painful and often the person who has them does not notice them, in the early stages of Parkinson’s, unless he or she happens to notice a hand that is trembling. Often using the limb that has tremors ends them, at least for the duration of the activity. However, tremors can become so severe that they cause nearly complete debilitation, interfering with coordination and dexterity to the extent that the person cannot hold objects or manage simple daily living tasks such as dressing. Tremors that affect the feet and legs can make walking difficult or impossible. When tremors do not respond to medication, sometimes surgery can relieve them.