Fig. 1.

Right posterior canalithiasis. In the upright position, the otoconia are positioned close to the ampulla of the right posterior canal. Only subtle spontaneous upbeat nystagmus was seen in this subject. During the right Dix-Hallpike test, the ampulla is brought to a higher gravitational point causing otoconia to gravitate away from the ampulla and generate a brief excitatory nystagmus which is upbeating with a rightward torsion. The nystagmus slow phase velocity (SPV) profile shows a brief onset latency, crescendo-decrescendo intensity pattern and short duration.