The otoliths are a chandelier-like structure hanging from the ceiling of the inner ear. As we move, its canals bend from side to side and we sense these movements. Like a chandelier, this structure is weighted by crystals. These tiny rocks can come loose and fall into the canals causing BPPV (benign paroxysmal positional vertigo).
Every time someone with BPPV does a particular head movement, for example putting their head back to look for something on an upper shelf or rolling over in bed, they get dizzy. This happens because the loose crystals overstimulate the movement sensors in the canal. There are canal-specific manoeuvres that can be performed by a doctor, audiologist or physiotherapist to shift the crystals back to where they belong.
Between 85 to 90% of BPPV affects the posterior canal; for most patients, it is easily fixed using the Epley manoeuvre. The Barbeque Roll (rotational) manoeuvre is used when the horizontal canal is affected. Read more about BPPV.