Fig. 4.

Right lateral canalithiasis. In the upright position, the otoconia are located in the long arm of the right lateral canal at a distance from the ampulla. There was no spontaneous nystagmus in this subject. During the right roll test, otoconia descend towards the ampulla creating an intense excitatory right-beating nystagmus. During the left roll test, otoconia gravitate away from the ampulla producing a less intense inhibitory left-beating nystagmus. The slow phase velocity (SPV) profiles for both roll tests show a brief duration nystagmus with a higher peak velocity reached during the right roll test.