Ménière's disease (MD) is an inner ear disorder in which the main pathological feature is endolymphatic hydrops (EH). Positive pressure therapy (PPT) using a portable device is now a second-line therapy for intractable MD when initial medical treatment fails. However, it remains unknown whether PPT causes the morphological and functional changes of inner ear in patients with active MD in accordance with reduction of vertigo attacks. In this nonrandomized controlled trial of 52 patients with MD, the volume of EH significantly decreased with reduction of vertigo attacks during 8 months of PPT combined with medications while the volume of that significantly increased with medications alone. There was no difference between Control group (n = 26) and PPT group (n = 26) regarding the vertigo control, however, PPT group achieved a significant functional improvement of vertical semicircular canals. The effect of volume reduction by PPT has been firstly demonstrated and the functional changes of all semicircular canals during PPT have been firstly examined. Morphological and functional changes in the inner ear by administrating local positive pressure are quite different from those caused by medications alone.Clinical trial registration: UMIN-CTR UMIN000041164 (registered on July 20, 2020).
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