Video head impulse test and seasickness susceptibility

Seasickness can have a devastating effect on a crewmember's well-being. In the literature, there is a controversy about whether car sickness could be diagnosed by vestibular evaluation tests, specifically by Video Head impulse test (vHIT) a semi-circular canal (SCC) function test. These consequences might be relevant to seasickness susceptibility. Angular acceleration at the pitch and roll planes lead to the development of seasickness. Normative data from vHIT indicates that the vestibulo-ocular reflex (VOR) gain for the anterior and posterior semicircular canals is lower and more variable compared to the lateral SCC VOR gain. It is expected that these differences will be evident in vHIT testing between individuals who are susceptible to seasickness and those who are not. Eighty-six maritime military personnel were assigned to the study. Participants were classified as non-susceptible based on Golding (1-3) and Motion sickness score ≥ 8. Seasickness-susceptible subjects were classified as Golding 6 and Motion sickness score ≤ 7. There was no significant difference in vertical VOR gains, asymmetry ratios, or the proportion of individuals with corrective saccades between the study groups. The results could not differentiate between study groups by the standard vHIT parameters. Further analysis of the left ipsilateral anterior to lateral vHIT mean VOR gain ratio has revealed a significantly lower ratio for the seasickness susceptible group (0.896 ± 0.126 and 0.963 ± 0.128 in seasickness susceptible and non-susceptible groups, respectively, Student's unpaired t-test, P = 0.0187; Cohen's d effect size 0.527543). This observation should be considered as an additional vHIT parameter when evaluating susceptibility to seasickness. This study was retrospectively registered on December 11th, 2022 and assigned the identifier number NCT05657340.