Evaluation of vestibulo-ocular reflex in motion sickness: A comparison of vHIT, SHIMP, and functional head impulse test

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Background Motion sickness (MS) is an autonomic condition triggered by real or perceived movement. No single objective test reliably identifies MS susceptibility or explains its vestibular basis. Objective To compare vHIT, SHIMP, and functional head impulse test (fHIT)—with and without optokinetic stimulation—in detecting vestibulo-ocular reflex (VOR) dysfunction in MS, and to examine links between MS susceptibility, dizziness-related handicap, and anxiety. Methods Thirty adults with MS and 30 healthy controls underwent vHIT, SHIMP, fHIT, and optokinetic fHIT (fHIT-OPK), along with the Motion Sickness Susceptibility Questionnaire–Short Form (MSSQ-SF), Dizziness Handicap Inventory (DHI), and State-Trait Anxiety Inventory (STAI). Results VOR gain did not differ significantly between groups on vHIT or SHIMP. fHIT percentage of correct answer (CA%) were significantly lower in the MS group for the right anterior ( p = 0.049), left anterior ( p = 0.001), and right posterior ( p = 0.015) canals. fHIT-OPK revealed additional impairment in the right lateral canal ( p = 0.031). DHI and STAI scores were significantly elevated in the MS group. MSSQ-SF correlated strongly with DHI total (r = 0.914) and moderately with state and trait anxiety (r = 0.541 and 0.551, respectively). Conclusions fHIT is more sensitive than vHIT and SHIMP in detecting VOR-related dysfunction in MS. Optokinetic stimulation unmasks visual-vestibular integration deficits. Subjective measures of handicap and anxiety should complement objective testing in this population.