The most common mechanism behind BPPV. Loose calcium carbonate crystals float freely inside a semicircular canal.
Medical definition
Canalithiasis (from the Greek: canal + stones) refers to free-floating otoconia inside one of the three semicircular canals. Under normal conditions, otoconia sit fixed in the otolithic membrane of the utricle. When they detach and enter a canal, head movement causes the debris to shift through the endolymph, creating abnormal fluid currents that deflect the cupula. The brain receives a rotational signal that does not match what the eyes and proprioception are reporting, and the result is vertigo. Episodes are typically brief – under a minute – because once the debris settles, the signal stops.
Why it matters
Canalithiasis accounts for the large majority of BPPV cases. Its counterpart, cupulolithiasis, is less common and behaves differently – the vertigo lasts longer because the crystals are stuck to the cupula rather than floating freely. Getting this distinction right matters because the two variants respond differently to repositioning. Canalithiasis responds well to the Epley maneuver (posterior canal), BBQ roll (horizontal canal), or Bangalore Maneuver (anterior canal). Cupulolithiasis often needs the Gufoni maneuver or a modified Semont.
Where I see this
The classic canalithiasis presentation is a patient who is fine all day and then gets a severe spinning episode when rolling in bed, looking up, or bending forward. The vertigo lasts 10 to 40 seconds and then stops. Nausea is common; hearing loss and tinnitus are not. When a patient has hearing loss alongside the vertigo, I look for Meniere disease or labyrinthitis, not BPPV. The Dix-Hallpike test in canalithiasis gives a brisk onset nystagmus with a fatigable response.
Related terms
Otoconia – the crystals that are displaced. Cupulolithiasis – the related variant. Semicircular canals – the anatomical space. Epley maneuver – repositioning procedure for posterior canal canalithiasis.
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