Age-related changes on the morphology of the otoconia.

OBJECTIVES/HYPOTHESIS: Although there are numerous reports on otoconial morphology using field-emission scanning electron microscopy (FESEM), there are few reports regarding the changes of otoconial morphology with aging. The aim of the current study was to investigate changes in otoconial morphology in rats according to age, using FESEM.

STUDY DESIGN: Laboratory study using experimental animals.

METHODS: We investigated age-related changes in otoconial morphology using FESEM in three groups of rats: young (1 wk old), middle-aged (6 mo old), and aged (23 mo old).

RESULTS: There was great size variation in utricular otoconia in the young and aged rats, but we found no clear regional separation of saccular otoconia in all groups based on size. In the oldest rats, the bodies of many otoconia in both maculae were pitted, fissured, penetrated, and eventually broken into several fragments. However, the terminal facets were smooth and the lines of intersection of facets were sharp, despite the degenerated bodies of the otoconia in this group. Giant otoconia were discovered frequently on the outer margin of the utricular maculae in aged rats. We directly observed weakened or broken linking filaments and otoconial fragments in the aged group.

CONCLUSION: The oldest rats showed the most degeneration of otoconia and linking filaments with otoconial fragments. This study of age-related morphologic changes in otoconia might help us understand the origin of idiopathic benign paroxysmal positional vertigo.