Quantitative tremor analysis can distinguish Parkinson disease (PD) from dopamine receptor blocking agent-induced parkinsonism, according to a recent study. Dual axis accelerometry was used to quantify tremor in 158 patients with parkinsonism; 62 had PD and 96 were clinically diagnosed with dopamine receptor blocking agent-induced parkinsonism. Tremor was measured while subjects rested arms (resting tremor), outstretched arms in front (postural tremor), and reached a target (kinetic tremor). Researchers found:

• Patients with dopamine receptor blocker induced parkinsonism had lower resting and postural tremor amplitude.
• There was a substantial increase of kinetic tremor amplitude in both disorders.
• Postural and resting tremor in subjects with dopamine receptor blocking agent-induced parkinsonism was prominent in the abduction–adduction plane.
• In contrast, the PD tremor had equal amplitude in all 3 planes of motion.
• Tremor frequency was comparable in both groups.