Measuring disease progression and disability in orthostatic tremor

To develop a questionnaire quantifying the impact of orthostatic tremor (OT) on patients' function and quality of life to enable longitudinal measurement of disease severity.

Patients with OT were interviewed in order to identify domains for a new disease-specific impact profile. The OT impact profile (OTIP) included forty-seven items across activities of daily living (9), mobility (9), social participation (2), assistance (8) and emotional effects (19) scored from 0 to 4 (total range 0-188). The same patients were invited to complete this at baseline and six-years later. An exploratory univariate linear regression analysis was performed to identify factors contributing to OTIP scores.

Thirty-three patients were initially interviewed. Twenty-one completed the OTIP at baseline and 16 at follow-up. Over time there was an increase in falls and requirement for gait aids. The mean total OTIP score at baseline was 96(SD 52). There was no significant difference in the mean total (84, p = 0.4) or sub-domain scores at follow up. Regression analysis found the utility of gait aids and disease duration to predict a worse score.

OT has a broad range of impacts on patients' quality of life and the OTIP appears to have some utility in measuring the functional impact. We found no change in overall disease impact on multiple domains over six years follow-up. This apparent lack of change may be due to the significant early impact that fear of falling has on patients.