Scales to evaluate psychosis in Parkinson's disease

Hallucinations and psychotic episodes are an important non-motor aspect of Parkinson’s disease but are frequently underreported by patients and unrecognised by both caregivers and physicians. Whilst a number of scales have been developed for scoring these behaviours often they have been adopted from other psychotic disorders, such as schizophrenia, and the psychotic episodes may differ considerably between the two diseases. In the current article, the author reports on the findings of a Movement Disorder Society task force that completed a systematic critique of available scales used in clinical trials focusing on hallucinations and psychosis. Several scales met the criteria to be classified as recommended, including the Neuropsychiatric Inventory, Brief Psychiatric Rating Scale, Positive and Negative Syndrome Scale, and Schedule for Assessment of Positive Symptoms. However, the task force identified inherent weaknesses in each scale and none could be identified as a definitive rating tool, indicating the requirement for a new Parkinson’s disease-specific scale to assess hallucinations and psychosis.