Associations Between the Vestibulo-Ocular Reflex and Cognitive Function in de novo Parkinson's Disease

Vestibulo-ocular reflex (VOR) impairment has been reported in Parkinson's disease (PD). However, its clinical implications, particularly with respect to cognition, remain unclear. We investigated canal-specific VOR changes and their associations with cognitive function, motor symptoms, gaits, and dopamine transporter (DAT) uptake in de novo PD patients.

We prospectively enrolled 127 patients with de novo PD who underwent video head-impulse tests (video-HITs), comprehensive neuropsychological assessments, gait analysis, and 18F-N-(3-fluoropropyl)-2β-carbon ethoxy-3β-(4-iodophenyl) nortropane positron emission tomography. Associations between VOR gains and the clinical characteristics of PD were evaluated using general linear models adjusted for age, sex, and education level. Cognitive analyses were performed after the patients were stratified into PD with normal cognition (PD-NC) and PD with mild cognitive impairment (PD-MCI) groups. Partial correlation analyses were performed to assess the relationships between VOR gains and regional DAT uptake.

Decreased VOR gain in at least one canal was observed in 22 patients (17.32%). Horizontal canal (HC) gain was positively associated with the Korean version of Montreal Cognitive Assessment score (p=0.040), and anterior canal (AC) gain was negatively associated with the base of support (p=0.018). The patterns of association between VOR gains and neuropsychological measures differed between the PD-NC and PD-MCI groups. In addition, VOR-cognition relationships were canal-specific: HC gain was positively related to visuospatial function, whereas AC and posterior canal gains were negatively related to language and frontal-executive functions. DAT uptake in the locus coeruleus was positively correlated with HC gain (p=0.020).

VOR integrity is associated with cognitive and gait function in patients with PD. Video-HITs may serve as potential biomarkers for disease monitoring in PD patients.