Unilateral vestibular weakness: an often under-recognized entity. Is symptom improvement feasible?

Abstract Objective To review the epidemiology, pathogenesis, diagnosis, and treatment of unilateral vestibular weakness (UVW), and critically assess the related evidence. Methods Literature research in Medline and other database sources until August 2020. Results The total number of included studies was 39. Conclusion The lifetime prevalence of UVW in the general population is 0.2%; the respective incidence is unknown. UVW frequently overlaps with other diagnoses; nevertheless, there is usually a history of a single, preceding, monophasic event. The respective criteria include unsteadiness of more than two months, clinical exclusion of BPPV, and exclusion of Meniere’s disease, central lesion, or bilateral vestibular dysfunction, and more than 25% inter-aural asymmetry in the caloric test. The latter represents the golden testing standard in suspected patients, and should be complemented with vestibulo-ocular reflex assessment via rotation-testing and video head-impulse test. Posturography can be useful to evaluate postural stability. Questionnaire-based assessments may assess symptom severity, the ensuing disability, and the subjective perception of patients’ overall balance status. MRI is advised in vertiginous patients in the presence of neurologic signs and symptoms, risk factors for cerebrovascular disease, or progressive unilateral hearing loss. Vestibular rehabilitation is effective in patients with UVW, whilst pharmacological treatment is of limited value.