canalithiasis

Canalolithiasis is a mechanism underlying benign paroxysmal positional vertigo (BPPV) in which free-floating otoconia—calcium carbonate crystals from the utricle—enter a semicircular canal, most commonly the posterior canal. When the head changes position relative to gravity, these particles move within the endolymph and deflect the cupula, triggering brief vertigo and a time-locked nystagmus.

Clinically, canalolithiasis presents as sudden episodes of vertigo provoked by specific head movements, such as looking up, lying down, or rolling in bed. Each episode typically lasts under one minute and may be accompanied by nausea. The accompanying eye movements (nystagmus) are usually direction-specific, often upbeating and torsional toward the affected ear. Vertigo and nystagmus tend to fatigue with repeated testing.

Diagnosis is mainly clinical, supported by positional testing. The Dix-Hallpike maneuver is used to provoke the characteristic vertigo and nystagmus when the implicated canal is oriented toward the bed. In canalolithiasis, symptoms and nystagmus are typically brief and diminish with repeated provocation, distinguishing it from cupulolithiasis, where debris adheres to the cupula and symptoms may persist longer.

Treatment focuses on repositioning the debris back into the utricle. First-line therapies are canalith repositioning maneuvers, such as the Epley or Semont maneuvers. Patients may perform home exercises or Brandt-Daroff routines if advised. Most individuals improve after one or a few sessions, though recurrences are common.

Prognosis is generally favorable with appropriate therapy. Risk factors include aging, prior head trauma, and degenerative changes of the vestibular system. Canalolithiasis is distinguished from cupulolithiasis by the behavior and duration of vertigo and nystagmus during testing.