Otoconial

Otoconial is an adjective relating to otoconia, the small calcium carbonate crystals in the vestibular system of the inner ear. These crystals are located in the utricle and saccule, embedded in the gelatinous otolithic membrane that overlies the maculae, the sensory epithelia that detect linear acceleration and head position relative to gravity.

Otoconial crystals are composed primarily of calcium carbonate, typically in calcite form, with a protein-rich organic matrix. Individual otoconia range from a few to several tens of micrometers in diameter. They are anchored to the otolithic membrane and together form an otolithic layer that contributes to gravity sensing by adding inertia to the system.

Functionally, when the head moves, the inertia of the otoconia causes a relative lag against the movement of the surrounding gelatinous membrane, deflecting the stereocilia of hair cells in the macula. This deflection modulates hair cell activity, sending signals via the vestibular nerve to the brain and helping to determine linear acceleration and head orientation.

Clinically, dislodgement or degeneration of otoconial material can lead to pathologies such as benign paroxysmal positional vertigo (BPPV), where free-floating otoconial debris enters the semicircular canals, most often the posterior canal. This can cause brief vertigo with certain head movements. Treatments include canalith repositioning maneuvers designed to move the debris back to the utricle.