The Functional Head Impulse Test to Assess Oscillopsia in Bilateral Vestibulopathy

Introduction: Bilateral vestibulopathy (BV) is a chronic condition in which vestibular function is severely impaired or absent on both ears. Oscillopsia is one of the main symptoms of BV. Oscillopsia can be quantified objectively by functional vestibular tests, and subjectively by questionnaires. Recently, a new technique for testing functionally effective gaze stabilization was developed: the functional Head Impulse Test (fHIT). This study compared the fHIT with the Dynamic Visual Acuity assessed on a treadmill (DVA(treadmill)) and Oscillopsia Severity Questionnaire (OSQ) in the context of objectifying the experience of oscillopsia in patients with BV.

Methods: Inclusion criteria comprised: (1) summated slow phase velocity of nystagmus of

Results: In total 23 patients were included. This study showed a moderate correlation between OSQ outcomes and the fHIT [rightwards head rotations (r(s) = -0.559; p = 0.006) leftwards head rotations (r(s) = -0.396; p = 0.061)]. No correlation was found between OSQ outcomes and DVA(treadmill), or between DVA(treadmill) and fHIT. All patients completed the fHIT, 52% of the patients completed the DVA(treadmill) on all speeds.

Conclusion: The fHIT seems to be a feasible test to quantify oscillopsia in BV since, unlike DVA(treadmill), it correlates with the experienced oscillopsia measured by the OSQ, and more BV patients are able to complete the fHIT than DVA(treadmill).