Effects of Intratympanic Injection of Isosorbide on the Vestibular Function of Animal Models of Endolymphatic Hydrops

Objectives. The aims of this study were to investigate the effect of intratympanic injection of isosorbide on the vestibular function in animal models with endolymphatic hydrops and to find a new treatment option for the acute onset of vertigo in Ménière’s disease (MD).Methods. Seventy male guinea pigs were used. Intratympanic injection of isosorbide (IT-ISB) was applied. The animals were divided into three study groups, namely the control, chronic hydrops model, and acute hydrops model groups. The intracochlear drug concentration was measured using high-performance liquid chromatography (HPLC). Vestibular function was analyzed using an animal rotator test with bidirectional sinusoidal harmonic acceleration (SHA) before and after IT-ISB. The histological change was also investigated.Results. ISB successfully permeated the perilymph through the round window membrane (RWM) at all three different concentrations of IT-ISB (25%, 50%, and 100%). In the chronic hydrops model, while IT-ISB histologically induced a reduction of endolymphatic hydrops, vestibular function was unchanged. In the acute hydrops model, no endolymphatic hydrops was histologically observed, and vestibular symmetry was also preserved after IT-ISB.Conclusion. ISB passed through the RWM into the perilymphatic space even at the lower concentrations. IT-ISB histologically reduced the hydrops in the chronic model and preserved the symmetrical vestibular function in the acute model. IT-ISB could be a treatment candidate for the acute attack of vertigo in MD.