Associated co-morbidities in a retrospective cohort of orthostatic tremor

Background Orthostatic tremor (OT) is characterized by tremor in orthostatism. Primary OT is characterized by a high-frequency tremor at surface EMG recording and assumed to be idiopathic, whereas slow-frequency OT is classically associated with neurological pathologies. We report here a retrospective monocentric cohort study of primary (fast OT) and pseudo-OT (slow OT) patients to describe associated neurological and non-neurological co-morbidities. Methods Between November 2014 and October 2019, 27 patients with OT were selected from the EMG database of the Department of Clinical Physiology in Lariboisiere' s hospital. Patients were classified in primary OT if tremor frequency was >= 13 Hz and in pseudo-OT if tremor frequency was < 13 Hz. Results Leg tremor on standing represented 10.2% of all tremor recordings. Ten patients were included in the primary and 17 in the pseudo-OT group. Females were predominant (62.9%) (p = 0.04). Mean age at diagnosis was 64.8 +/- 1.1 years. At the first visit, a movement disorder was associated with 30% of primary OT, among them one CADASIL patient, whereas extrapyramidal or cerebellar disorders were reported in 100% of pseudo-OT, among them three Wilson's disease patients. These pathologies all preceded primary OT and occurred concomitantly with pseudo-OT. Frequency remained unchanged during evolution, except pseudo-OT in two patients that completely resolved following the introduction of antiParkinsonian drugs. Treatment of primary OT was partially effective in 28% and in 50% of pseudo-OT patients. Conclusion In this monocentric study, movement disorders were present in 30% of primary OT patients. This result questions the term idiopathic or primary OT, but the small number of patients does not allow answering this issue.

Automated summary

This retrospective study analyzed 27 OT patients and found associations between movement disorders and OT, but further research is needed to classify OT (primary or pseudo).