Taresa Stefurak MSc, MD, FRCPC, Neuropsychiatry Fellow, Rotman Research Institute, Baycrest Centre for Geriatric Care, University Health Network, Department of Neurology, University of Toronto, Toronto, ON.
Although Parkinson's disease (PD) is by definition a movement disorder, with a clinical diagnosis made by the presence of two out of three cardinal levodopa-responsive motor signs (tremor, rigidity, bradykinesia), both cognitive and neuropsychiatric symptoms are also important components. The clinical impact of these neurobehavioural symptoms is supported by a study in which the strongest predictor of quality of life perceived by PD patients was the presence of depression.1 Cognitive impairment as well as postural instability and disability also contributed to poor quality of life. Behavioural disturbances and dementia are the primary reasons for nursing home placement in PD patients.2
Characterizing the nature of these symptoms in PD provides an important model to understand the underlying mechanisms of disease progression and brain function. Although psychosocial aspects may play a role in some of the behavioural and mood disturbances in PD, evidence suggests that the underlying mechanism for these symptoms arises from the biological dysfunction of anatomical and neurochemical substrates that occur in PD.