Clinical Characteristics of Primary Orthostatic Tremor - a Comprehensive Clinical Assessment of Patients in Sweden.

Background: Primary orthostatic tremor (POT) is a rare neurological disease presenting as a bilaterally coherent tremor of 13-18 Hz and a subjective sensation of unsteadiness while standing. Patients are severely affected by the inability to stand and often eventually referred to walking aids and dependence on others. Objectives: This study aimed to investigate the clinical characteristics of POT in a Swedish patient population by interviews and questionnaires. Methods: Patients with POT were recruited nationwide in Sweden. All participants underwent neurological examination, structured interview and evaluation according to nine standardized rating scales and questionnaires, including the novel orthostatic tremor scales OTIP and OT-10. Results: Fifty-two participants with EMG-verified POT were included in the final analysis. Disease duration was not significantly correlated to disease severity, while OTIP and OT-10 were highly correlated with severity of POT. Postural or action tremor in the arms were present in 58%. Mild signs of parkinsonism were common, and the combination of mild rigidity and bradykinesia was present in 25%. Symptoms of depression and anxiety were present in 25%. Although quality of life was often severely affected, 65% performed activities of daily life independently. Discussion: Patients with POT may be severely affected by their disease, independently of disease duration. Multiple associated symptoms like tremor in the upper extremities and mild Parkinsonian features need to be recognized by healthcare professionals. Highlights: 52 patients with POT were clinically examined with rating scales and questionnaires. Additional symptoms like other tremors, parkinsonian signs, and depressive symptoms were common. Disease severity did not correlate to additional symptoms or disease duration. Questionnaires like OTIP and OT-10 can be recommended for assessment of disease severity.