Continuous vertigo and spontaneous nystagmus due to canalolithiasis of the horizontal canal.

The authors present a patient with benign paroxysmal positional vertigo of the right horizontal semicircular canal who developed persistent vertigo with spontaneous horizontal nystagmus to the left and caloric hypoexcitability on the right after a head shaking maneuver. Both spontaneous nystagmus and canal paresis resolved after repeated shaking of the head. The most probable mechanism of this type of vertigo is plugging of the horizontal canal by otoconial particles with a negative endolymph pressure between plug and cupula.