This patient has an asymmetric resting tremor, consistent with Parkinson's disease. A resting tremor is a rhythmic oscillation of a limb that occurs at rest and diminishes with activity. Resting tremor results from basal ganglia dysfunction. This can be due to either reduced dopaminergic output of the substantia nigra, such as occurs in idiopathic Parkinson's disease, or blockade of the postsynaptic dopamine receptors in the basal ganglia, such as occurs in drug-induced parkinsonism.