Parkinson’s disease (PD) is the second most common neurodegenerative disease and affects more than one million people in the US.1 The cause of PD is unknown, but it involves the loss of dopaminergic neurons in the substantia nigra pars compacta of the midbrain. Clinically, PD is characterized by the triad of rigidity, bradykinesia, and rest tremor, and is often associated with postural instability. While motor disability is the hallmark of PD, there is a whole spectrum of non-motor manifestations that can significantly contribute to the disease-related disability.

There are two commonly used scales to measure PD-related disability and severity of the disease. The Hoehn and Yahr Scale is a measure of overall severity of PD, with a score of zero indicating no disease and a score of five indicating end-stage disease.2 The Unified Parkinson’s Disease Rating Scale (UPDRS) consists of four parts.3,4 Part I is a brief evaluation of mentation, behavior, and mood; part II assesses activities of daily living (ADL); part III is objective assessment of motor disability; and part IV is assessment of complications of therapy (i.e. dyskinesia and motor fluctuations).

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