Objective: To investigate markers of autoimmunity in plasma and cerebrospinal fluid (CSF) in a prospective cohort of patients with OT evaluated at a tertiary movement disorders centre.

Background: Orthostatic tremor (OT) is a rare and likely underdiagnosed movement disorder characterised by a high-frequency tremor of the lower limbs that emerges during standing or weight-bearing and improves when sitting or walking (1). The pathophysiology remains uncertain, with current hypotheses suggesting dysfunction of a central oscillator or disruption of the cerebello-brainstem-thalamo-cortical network involved in postural control. Immune mechanisms have been proposed as a potential contributor in some cases, supported by reports of OT associated with paraproteinaemia and inflammatory CSF findings, making the evaluation of autoimmune markers clinically relevant.

Method: We analysed a prospective cohort of 21 patients with OT. Diagnosis was based on clinical symptoms and examination findings and confirmed in all patients by electrophysiological studies demonstrating high-frequency OT. Paired plasma and CSF samples were collected and analysed for markers of autoimmunity.

Results: Twenty-one patients were included. Mean age was 65.6 ± 8.7 years (range 51–80), with a female predominance (17/21, 81%). Serum immunoelectrophoresis identified monoclonal paraproteins in three patients (3/21, 14%), higher than the approximately 4–5% prevalence reported in age-matched populations (3). CSF abnormalities were observed in a subset of patients, including pleocytosis in three (14%), elevated protein in four (19%; up to 0.79 g/L), and oligoclonal band abnormalities in two (9.5%).

Conclusion: This prospective cohort represents one of the largest OT series in which serum and CSF autoimmune markers were systematically evaluated. Although most tests were negative, isolated abnormalities were detected. As a descriptive case series, these findings are hypothesis-generating but suggest that immune mechanisms may contribute to OT in a subset of patients and justify further investigation in larger cohorts.

References: Af Edholm, K., Uribarri, G., Sundgren, M., Svenningsson, A., Fransén, E., 2026. Orthostatic Tremor Is Evoked by Muscle Load Without the Need for Orthostatic Position. Movement Disord Clin Pract 13, 208–215. https://doi.org/10.1002/mdc3.70270

Phipps, C.J., Whitney, D., Shou, J., Torres-Russotto, D., Warren, D.E., 2024. Measurement of Functional Brain Network Connectivity in People with Orthostatic Tremor. Brain Sciences 14, 219. https://doi.org/10.3390/brainsci14030219

Rajkumar, S.V., Kumar, S., 2025. Monoclonal Gammopathy of Undetermined Significance. N Engl J Med 393, 1315–1326. https://doi.org/10.1056/NEJMra2412716

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MDS Abstracts - https://www.mdsabstracts.org/abstract/plasma-and-csf-autoimmune-markers-in-orthostatic-tremor-insights-from-a-prospective-tertiary-centre-cohort/