Six-canal video head impulse test in patients with labyrinthine and retrolabyrinthine pathology: detecting vestibulo-ocular reflex deficits.

ABSTRACT

BACKGROUND: Abnormal gains in six-canal video head impulse test are attributed to semi-circular canal deficits. However, as video head impulse test responses are linked to the vestibulo-ocular reflex, it was hypothesised that abnormal gains can be caused by vestibulo-ocular reflex pathway deficits. METHODS: This study compared video head impulse test gains in 20 patients with superior semi-circular canal dehiscence (labyrinthine cause) and 20 side- and gender-matched patients with vestibular schwannomas (retrolabyrinthine cause), and investigated correlations between them (Mann-Kendall trend test). RESULTS: Vestibular schwannoma but not superior semi-circular canal dehiscence was significantly associated with abnormal lateral (odds ratio = 9.00 (95 per cent confidence interval = 1.638-49.44), p = 0.011) and posterior (odds ratio = 9.00 (95 per cent confidence interval = 2.151-37.659), p = 0.003) canal status. In vestibular schwannoma patients, there was a statistically significant degree of dependence between all ipsilesional canal video head impulse test gains; such dependence was not observed in superior semi-circular canal dehiscence. CONCLUSION: Vestibulo-ocular reflex gains differ in patients with labyrinthine and retrolabyrinthine disease; this suggests that abnormal gains can indicate deficits not only in the semi-circular canals but also elsewhere along the vestibulo-ocular reflex pathway.