Objective: To determine if people with Parkinson’s disease (PD) have greater vestibular dysfunction than age-matched healthy people (HC).

Background: The vestibular system is crucial for postural stability. It comprises otoliths which detect verticality (static function) and linear acceleration (dynamic function), and semi-circular canals (SCCs) which detect angular velocity. Evidence of vestibular function in people with PD show conflicting results. Compared to HC, people with PD have been reported to have dynamic otolithic pathway dysfunction [1] yet abnormally increased horizontal VOR gains [2].

Method: 40 PD (68% male) and 40 HC (63% male) participated (mean age 70 years). Dynamic otolithic function was determined by ocular and cervical Vestibular Evoked Myogenic Potentials (oVEMPs and cVEMPs, respectively) through air-conducted stimuli (ACS, mono-aural clicks) and bone conducted vibration (BCV, tendon hammer taps). Horizontal and vertical SCC function was determined through video head impulse testing (vHIT) and tracings with artefacts were excluded. Static otolithic function was determined via subjective visual vertical (SVV) and mean absolute angle error was calculated. Between group differences were determined using t-tests or Fisher’s exact test for cells with small values.

Results: Horizontal and vertical SCC vHIT gains were not significantly different between groups (p>0.10). In contrast to Lv et al [2], VOR gain for horizontal canals was not increased in people with PD.  Compared to HC, people with PD had significantly more absent cVEMP responses (BCV bilaterally, p≤.01; left-sided ACS p=.02). Both groups had similar oVEMP responses (p>.19), with ACS-obtained responses predominantly absent but BCV-obtained responses largely intact. Latency (p>.05) and amplitude (p>.62) of present VEMP reflexes were not significantly different between groups. People with PD had greater error on the SVV test compared to HC (p=.001).

Conclusion: People with PD do not have significant impulsive VOR gain differences (vHIT) or utriculo-ocular reflex differences (oVEMP) compared to HC. However, vestibulo-spinal reflex pathways as measured by cVEMP are more frequently absent in PD. SVV absolute error angle was also significantly different and showed greater variability in PD, suggesting a perceptual impairment of verticality.

References: [1] Venhovens et al. Neurovestibular analysis and falls in Parkinson’s disease and atypical parkinsonism. Eur J Neurosci 2016;43:1636-46. [2] Lv et al. Vestibulo-ocular reflex abnormality in Parkinson’s disease detected by video head impulse test. Neurosci Lett 2017;657:211-14.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/an-overview-of-vestibular-function-in-parkinsons-disease/