Functional and gain-based vestibulo-ocular measures across serum 25(OH)D categories: a dissociation between fHIT performance and vHIT gain
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Testing of all Six Semicircular Canals with Video Head Impulse Test Systems
Published on: April 18, 2019
Nazli Akkaya Kurt1, Özlem Ertuğrul2, Sadiye Murat Acar3
1Faculty of Health Sciences, Department of Audiology, Istanbul Gelisim University, Istanbul, Türkiye.
Background:
Conventional vestibular tests quantify canal and otolith function, whereas the functional head impulse test (fHIT) measures how effectively the vestibulo-ocular reflex stabilizes vision during high-acceleration head motion. Low 25-hydroxyvitamin D [25(OH)D] has been linked to otolith dysfunction, but its relation to functional performance is unknown.
Objectives:
To compare otolith, canal and functional measures across serum 25(OH)D categories in adults without overt vestibular disease.
Materials And Methods:
Thirty-nine adults aged 18-65 years with normal hearing were stratified by serum 25(OH)D into three groups of 13 (<20, 20-29.9, ≥30 ng/mL). All underwent audiometry, videonystagmography, cVEMP, oVEMP, vHIT and fHIT. Kruskal-Wallis and Mann-Whitney U tests were used.
Results:
fHIT correct response rates differed for posterior (p = 0.001) and anterior canals (p = 0.019), being lowest at <20 ng/mL; lateral performance was preserved (p = 0.234). All vHIT gains remained within acceptable limits and only anterior canal gain differed (p = 0.001). VEMP latencies were comparable; cVEMP amplitude asymmetry differed (p = 0.023) but opposite to expectation and within normal range.
Conclusions And Significance:
Low 25(OH)D was accompanied by reduced functional vestibulo-ocular performance in the vertical canal planes despite normal gains. fHIT may capture subclinical change that vHIT gain does not.
