Changes in the cupula after disruption of the membranous labyrinth

Abstract

Conclusion: Various changes were observed in the cupula, including shrinkage and enlarged volume, following the disruption of the membranous labyrinth. Cupular change after membranous labyrinth disruption may be a pathology of vestibular disorders. Objectives: To observe the morphological changes of the cupula after disruption of the membranous labyrinth and to compare the cupular changes with changes in the compound action potential (CAP) of the ampullary nerve. Methods: A labyrinthine injury model was created by puncturing the membranous labyrinth of bullfrogs. The cupula was observed from 3 to 17 days after the membrane puncture. The CAP in response to mechanical endolymphatic flow was recorded from the ampullary nerve. The correlation between cupular change and CAP positivity was evaluated using the authors' scale. Results: Various kinds of cupular changes including shrinkage were observed. Cupular change was more severe after a longer survival period. Large or elongated volume of the cupula was also observed, which was not observed in our previous study using gentamicin. The CAP could be recorded even when the cupular change was severe.

Keywords::

• Semicircular canal
• sensory epithelia
• compound action potential
• vestibular disorder

Acknowledgments

This study was supported by the Health and Labor Science Research Grants for Research on Specific Disease (Vestibular Disorders and Inner Ear Disorders) from the Ministry of Health, Labor and Welfare, Japan (2011) and the Grant-in Aid for Scientific Research (C) provided by the Ministry of Education, Science and Culture, Japan (2011). The authors are indebted to Mr R.J. Turner, Assistant Professor E.F. Barroga, and Professor J.P. Barron, Chair of the Department of International Medical Communications at Tokyo Medical University, for their editorial review of the English manuscript.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.