Which canal is most commonly affected in canalithiasis?

The most commonly affected canal in canalithiasis is the posterior canal. Canalithiasis refers to a condition involving the displacement of calcium carbonate crystals (otoliths) within the inner ear's semicircular canals. The posterior canal is particularly susceptible to this condition due to its anatomical position and the gravitational effects on the displaced otoliths when a person changes head positions.

When crystals migrate into the posterior canal, they can lead to symptoms characteristic of benign paroxysmal positional vertigo (BPPV), such as episodes of vertigo triggered by specific changes in head position. The posterior canal's position allows for the crystals to induce a strong response in the vestibular system, leading to a quick onset of vertigo.

Other canals, while they can also be affected (with the horizontal canal being the second most common), do not have the same propensity for canalithiasis as the posterior canal. This anatomical and physiological understanding clarifies why the posterior canal is recognized as the primary site involved in this condition.