Evaluating the Effects of Levodopa on the Vestibulo-Ocular Reflex in Parkinson’s Disease: A Case Series

Abstract

Purpose: Parkinson’s disease (PD) is a neurodegenerative disorder primarily affecting individuals over 60 years old. The disorder is characterized by motor symptoms due in large part to the loss of dopamine-producing neurons. The vestibular system, crucial for maintaining balance, may be impacted in PD, con­tributing to balance issues through dysfunction in the vestibulo-ocular reflex. In this study, we aim to describe differences in vestibular responses before and after use of levodopa (L-DOPA) in patients with PD. Method: The study evaluated nine PD patients who underwent videonystagmo­graphy, video head impulse testing, and rotational chair testing both on and off their dopaminergic medications. Effect sizes of the mean difference was mea­sured using Cohen’s d. Results: The results revealed a general trend of increase in vestibular responses from the off stage to the on stage across all the vestibular testing mechanisms. The p values were all > .05, and the Cohen’s d 95% confidence interval (CI) ranged from small to moderate effects with wide CIs consistent with the small sample. Conclusions: In this case series of nine patients with PD, we identified a gen­eral trend of a small increase in vestibular responses in the on state of L-DOPA compared with the off state of L-DOPA. The significance and clinical implications of such differences should be evaluated in larger samples.