Development and psychometric evaluation of a scale to measure impaired self-awareness of hyper- and hypokinetic movements in Parkinson’s disease

Objective: Patients with Parkinson’s disease (PD) can show impaired self-awareness of motor deficits (ISAm). We developed a new scale that measures ISAm severity of hyper- and hypokinetic movements in PD during medication on state and defined its psychometric criteria. Method: Included were 104 right-handed, non-depressed, non-demented patients. Concerning ISAm, 38 motor symptoms were assessed using seven tasks, which were performed and self-rated concerning presence of deficit (yes/no) by all patients. The whole procedure was videotaped. Motor symptoms were then evaluated by two independent experts, blinded for patient’s ratings, concerning presence, awareness of deficit, and severity. Exploratory principal component analysis (promax rotation) was applied to reduce items. Principal axis factoring was conducted to extract factors. Reliability was examined regarding internal consistency, split-half reliability, and interrater reliability. Validity was verified by applying two additional measures of ISAm. Results: Of the initial 38 symptoms, 15 remained, assessed in five motor tasks and merged to a total severity score. Factor analysis resulted in a four factor solution (dyskinesia, resting tremor right hand, resting tremor left hand, bradykinesia). For all subscales and the total score, measures of reliability (values 0.64–0.89) and validity (effect sizes>0.3) were satisfactory. Descriptive results showed that 66% of patients had signs of ISAm (median 2, range 0–15), with ISAm being most distinct for dyskinesia. Conclusions: We provide the first validation of a test for ISAm in PD. Using this instrument, future studies can further analyze the pathophysiology of ISAm, the psychosocial sequelae, therapeutic strategies and compliance with therapy. (JINS, 2015, 21, 1–10