Otolithiasis in the Animal Kingdom: A Retrospective Analysis.

Hypothesis: If otolithiasis can be demonstrated to affect multiple species, it may be possible to identify an experimental animal for prospective study of this entity.

Background: Otolithiasis refers to dislodged otolithic matter within the confines of the membranous labyrinth that has the potential to cause clinical symptoms. The mechanism involves separation of free-floating otoconia that can affect the hearing and balance functions of the ear. While this process is known to occur in humans, it is uncertain if other species are affected.

Methods: The published images of 37 whole-mount specimens of mammalian labyrinths were identified for retrospective examination. These were evaluated stereographically for the presence of calcareous material in abnormal locations within the membranous labyrinth.

Results: Thirty normal labyrinth specimens were found, exemplified by that of the Cape sea lion. Seven pathologic specimens were found, including a human, a black ape, a yellow-faced baboon, a hocheur monkey, a collie dog, a common sheep, and a common hare. Abnormal accumulations of calcareous material were found at one or more sites, more frequently in the utricle and canal system and less frequently in the endolymphatic and cochlea ducts.

Conclusions: Otolithiasis appears to occur in other animal species besides the human. Abnormal calcareous material was found in various locations within the membranous labyrinth of affected animals. One or more of these might serve as an animal model to prospectively study the phenomenon of otolithiasis.