ORTHOSTATIC TREMOR: DISEASE IMPACT AND PROGRESSION (P6.063)

Objective: To describe the clinical features of orthostatic tremor (OT) in a first ever prospectively studied cohort and to develop a disease specific questionnaire quantifying disease impact on patients’ function and quality of life. Background: OT is a rare condition characterized by unsteadiness on standing with an associated 13–18Hz leg tremor, with few therapeutic options. There are no established, objective markers of disease severity. Design/Methods: Patients fulfilling diagnostic criteria for OT completed a questionnaire regarding clinical characteristics, medication response, fall frequency and the use of gait aid. Patients with OT in isolation were classified Primary OT, while those with additional neurological signs OT-plus. Interviews identified domains for inclusion in a novel 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. Internal consistency and retest correlation was assessed. Results: Thirty-three patients were enrolled with sixteen available for follow-up. No differences were noted between primary OT and OT-plus patients. Medication use reduced over time and benefits appear diminished. One patient received deep brain stimulation with an excellent and enduring response. Falls increased over time (44% vs 6%, p=0.02) as did the utility of gait aids (33% to 67%, p=0.02). The mean total OTIP score at baseline was 96(SD 52) with no difference at follow up (84, p=0.4). There was no difference in 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 in future studies. Disclosure: Dr. Vijiaratnam has nothing to disclose. Dr. Siresena has nothing to disclose. Dr. Paul has nothing to disclose. Dr. Bertram has nothing to disclose. Dr. Williams has nothing to disclose.