Relationship between changes in hearing function and volumes of endolymphatic hydrops after endolymphatic sac drainage

Background: Endolymphatic sac drainage (ELSD) may have a positive effect on endolymphatic hydrops (EH) and may help to preserve inner ear function. However, the relationship between changes in EH volumes and hearing function after ELSD has not been described.Objectives: We aimed to reveal the factors related to changes in hearing and EH following ELSD.Material and Methods: Twenty-one patients who received ELSD were enrolled. Pure tone audiometry and 3-T magnetic resonance imaging (MRI) 4 h after intravenous injection of gadolinium enhancement were performed just before surgery and 2 years later. To characterize the endolymphatic space (ELS), we measured the volume of the total fluid (TFS) and ELS and calculated the ratio of ELS to TFS (ELS ratio).Results: The ELS ratio of the patients who showed hearing improvement was 18.5 ± 11.4% before surgery and 23.9 ± 14.3% after. For those with no change, it was 29.7 ± 10.8% before and 29.4 ± 9.5% after, and in patients with worsened hearing function it was 22.7 ± 7.5% before and 27.2 ± 13.4% after.Conclusion: We found no correlation between the changes in hearing function and the volume of EH after ELSD.