Ocular Vestibular-Evoked Myogenic Potential Assists in the Differentiation of Multiple System Atrophy From Parkinson's Disease.

Objective: Vestibular-evoked myogenic potentials (VEMPs) can help in assessing otolithic neural pathway in the brainstem, which may also contribute to the cardiovascular autonomic function. Parkinson's disease (PD) is associated with altered VEMP responses; however, the associations between VEMP abnormalities and multiple system atrophy (MSA) remain unknown. Therefore, we compared the extent of otolith dysfunction using ocular (oVEMP) and cervical VEMPs between patients with MSA and PD.

Methods: We analyzed the clinical features, VEMP, and head-up tilt table test (HUT) findings using the Finometer in 24 patients with MSA and 52 with de novo PD who had undergone neurotologic evaluation at a referral-based university hospital in South Korea from January 2021 to March 2023.

Results: MSA was associated with bilateral oVEMP abnormalities (odds ratio [95% confidence interval] = 9.19 [1.77-47.76], p = 0.008). The n1-p1 amplitude was negatively correlated with the Unified Multiple System Atrophy Rating Scale I-II score in patients with MSA (r = -0.571, p = 0.033), whereas it did not correlate with the Movement Disorder Society-Unified Parkinson's Disease Rating Scale-III score in patients with PD (r = -0.051, p = 0.687). The n1 latency was negatively correlated with maximum changes in systolic blood pressure within 15 s during HUT in patients with PD (r = -0.335, p = 0.040) but not in those with MSA (r = 0.277, p = 0.299).

Conclusion: Bilaterally abnormal oVEMP responses may indicate the extent of brainstem dysfunction in MSA. oVEMP reflects the integrity of otolith-autonomic interplay, reliably assists in differentiating between MSA and PD, and helps infer clinical decline.