Orthostatic tremor: disease progression and measuring disability

Objectives To describe the clinical features and disease severity in a prospectively studied cohort with orthostatic tremor (OT). Methods Patients fulfilling the diagnostic criteria for OT completed a questionnaire regarding clinical characteristics, medication response, fall frequency and the use of gait aids. Patients with OT in isolation were classified Primary OT, while those with additional neurological signs OT-plus. Interviews identified domains for inclusion in a new OT Impact Profile (OTIP). Forty-seven items across activities of daily living (9), mobility (9), social participation (2), assistance (8) and emotional effects (19) were drafted. Scores of 0–4 were given and the same patients were invited to complete the final OTIP (score range 0-188). This was repeated at 6 years. Results Thirty-three patients were enrolled with a mean disease duration of 12.6 years. The mean age was 74 years with a female predominance (n=30). Twenty-six patients (79%) had isolated OT. At baseline 85% of patients were taking medications but only 50% reported a benefit. After six years only 54% of patients were taking medications. Over six years we noted an increase in the number of falls reported (44% vs 6%, p=0.02). The proportion requiring gait aids also increased from 33% to 67% (p=0.02). All 33 patients were interviewed and completed the OTIP. After six years 16 patients completed the OTIP. The mean total OTIP score at baseline was 96 (SD 52) with no difference at follow up (84, p=0.4). There was also no difference in mean sub-domain scores. Excellent internal reliability and test-retest correlation was noted. Conclusions We present the first prospectively followed OT cohort. Although gait and mobility issues emerge, we found no change in the impact of OT on quality of life measures contrary to previous retrospective studies. The OTIP may be a useful marker of disease severity in future studies.