Otoconia in health and disease. A review.

Mammalian otoconia are made up of inorganic calcium carbonate crystallites and organic substance, which is thought to be sulfated glycosaminoglycans and glycoprotein. Mouse otoconia are formed in situ, and the primitive otoconia assume spindle, trigonal, dumbbell, or quadrilobed forms. As the otoconia mature, they assume the typical barrel-shaped body with pointed tips formed by three surfaces. A variety of otoconial disorders have been reported. Otoconial degeneration can result from ototoxic drugs, infection, trauma, and aging. Abnormal otoconia are also known to occur as a result of genetic mutation, as well as ototoxicity. Otoconial deficiency may be genetic or caused by certain drugs, such as carbonic anhydrase inhibitors or tetracycline, or manganese deficiency during the critical period of gestation when the otoconia are formed in utero. Otoconial deficiency has been found to produce head tilting, swimming difficulty, and reduction or failure of the air-righting reflexes in animals.