Paired neurophysiological and clinical study of the brainstem at different stages of Parkinson's Disease.

Objective: To study brainstem function in Parkinson's Disease (PD) at different stages, through a battery of vestibular-evoked myogenic potentials (VEMPs) and compare the results with scores on clinical scales assessing the presence of symptoms linked to brainstem involvement.

Methods: Cervical, masseter and ocular VEMPs were recorded in patients with early PD (n=14, disease duration 1.42±0.7years), advanced PD (n=19, disease duration 7.26±2.9years) and in 27 age-matched controls. In PD, the following clinical scales were administered: Mini-BESTest, REM sleep Behavior Disorder Screening Questionnaire (RBD-SQ), PD Sleep Scale, Epworth Sleepiness Scale and Geriatric Depression Scale.

Results: Rate of VEMPs alterations was higher (p<0.001) in PD than controls, but similar within PD groups. However, early and advanced PD showed a different pattern of abnormalities (p=0.02), being latency delay prevalent in the former and absence in the latter. VEMP impairment correlated directly with RBD-SQ scores in both PD cohorts and inversely with Mini-BESTest scores in advanced PD.

Conclusions: VEMPs displayed progressive severity of alterations at different stages of PD, with remarkable correlations with presence of postural instability and RBD.

Significance: The combined use of VEMPs may provide interesting insights into the pathophysiological mechanisms of PD at the earliest and prodromal stage of the disease.