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A calcareous concretion on the end of a sensory hair cell in the vertebrate ear and in some invertebrates.



a solid formation on the surface of the mechanoreceptor cells in the organs of equilibrium of some invertebrates and all vertebrates. Otoliths of different animals vary in origin, size, and structure: they can be secreted by cells or introduced from outside, for example, grains of sand serve as otoliths in crayfish. Mammalian otoliths are usually crystals of calcite (CaCO3) up to 10 microns (μ.) long and 1–3 μ wide.

As otoliths shift in response to acceleration and changes in body position, they mechanically irritate the underlying ciliated receptor cells, which then send appropriate signals to the brain.

The action of otoliths has been demonstrated in experiments with crayfish. The grains of sand that serve as the crayfish’s otoliths were replaced during molting by iron filings, and a magnet was placed above the animal to attract the filings. The crayfish reversed its sense of orientation, turned over, and swam with its abdomen up.


References in periodicals archive ?
Canalithiasis refers to the displacement of otoconia located within the gelatinous membrane in the macula into the semicircular canals, whereas cupulolithiasis defines the adherence of these particles to the cupula of the semicircular canals.
The short and relatively symmetrical onset latencies we recorded with the affected and unaffected ears down in canalolithiasis imply a rapid movement of the otoconia in the horizontal canals in response of provocative testing.
The primary diagnosis on Day One of BPPV prompted using the canalith repositioning manoeuvre (CRM) described by Epley (1992) to reposition the otoconia suspected to be present in the right posterior semi-circular canal (refer to Figures 1A-1E).
Hain et al mathematically simulated episodes of canalithiasis when otoconia fell from different positions.
If the otoconia break off, they can roll around and stimulate hair cells lining the semicircular canals, creating the spinning sensation of benign paroxysmal positional vertigo (BPPV).
With BPPV, the doctor moves the patient's head and body in a series of different positions, called the Epply maneuver, to get the otoconia back into their proper place, which stops the spinning sensation.
BPV occurs when otoconia dislodge from the utricle and lodge in the semicircular canals.
Decreased estrogen levels may disturb the internal structure of the otoconia or their interconnections and attachments to the gelatinous matrix.
This is unlike mammalian and some fish otoconia that are composed of a calcite crystal form of calcium carbonate (Dilly, 1976).
It's thought that the movement of small, naturally occurring crystals, called otoconia, from one part of the inner ear to another, interfere with the semicircular canals in the inner ear that affect balance, and cause the condition.
Schuknecht proposed that BPPV occurs when otoconia irritate the ampulla of the posterior semicircular canal (the cupulolithiasis theory), but other theories exist, as well.
BPPV occurs when the otoconia break loose and stimulate nerve endings in the canals that send a false signal of movement to your brain, causing vertigo.