Discrepancies between video head impulse and caloric tests in patients with enlarged vestibular aqueduct.

Objective: We performed the video head impulse test (vHIT) and caloric test in patients with enlarged vestibular aqueducts (EVA). We compared the results with those found in Ménière's disease (MD) and acute vestibular neuritis to clarify the characteristics of vestibular dysfunction in EVA and to suggest reasons for the discrepancy between the vHIT and caloric tests in endolymphatic hydrops.
Study Design: Retrospective analysis.
Methods: Ten patients with EVA and confirmed biallelic SLC26A4 genetic mutations were enrolled. The results of video head impulse and caloric tests were analyzed and compared with those of patients diagnosed with MD (n = 76) or acute vestibular neuritis (n = 19).
Results: Among patients with EVA, 40% showed unilateral caloric weakness and 30% had recurrent episodes of vertigo. All patients with recurrent vertigo had caloric weakness. However, only 25% of patients with abnormal caloric test results had abnormal vHIT results. The discrepancy between the caloric test and vHIT results was also found in patients with MD, but not in patients with acute vestibular neuritis (abnormal vHIT results in 47.3% and 94.7% of patients with unilateral caloric weakness, respectively).
Conclusion: Unilateral vestibular dysfunction was identified in 40% of patients with EVA by the caloric test, but caloric test results were not correlated with vHIT results. This finding was similar in patients with MD. Hence, it is possible that endolymphatic hydrops, a common pathologic feature of both EVA and MD, could cause the discrepancy, and that vestibulopathy in endolymphatic hydrops might be restricted to the low-frequency range.
Level of Evidence: 4. Laryngoscope, 127:921-926, 2017.
(© 2016 The American Laryngological, Rhinological and Otological Society, Inc.)