Fig. 7.

Canalithiasis benign paroxysmal positional vertigo (BPPV). A: canalith particles resting at the lowest point in the posterior canal. AC, anterior semicircular canal; PC, posterior canal; LC, lateral canal; U, utriculus. B: Dix-Hallpike maneuver positions the canal for particles to sediment ampullofugual down the lumen causing excitatory deflection of the cupula. C and D: for steady sedimentation, the total drag force balances the gravitational force arising from the total particle mass. E: the drag force F generated by the sedimenting canaliths is divided between viscous drag on the lumen of the duct and force on the cupula. F: if the particle sediments close to the inside wall, the viscous drag increases and the sedimentation velocity slows. G: predicted cupula volume displacements evoked by the Dix-Halpike maneuver for particles of different size but equal total mass. Large particles sediment faster than small particles resulting in shorter latency responses. If particles come to a rest before the cupula has fully deflected, the magnitude of the response will be reduced (specific simulations for α = 1). [A, B, and G: adapted from Rajguru et al. (2004).]