Abstract
Canalolithiasis and cupulolithiasis are known to be a primary etiology of benign paroxysmal positional vertigo (BPPV). In lateral canal type BPPV (L-BPPV), direction-changing geotropic or apogeotropic nystagmus is present. In many cases, the latency is long in canalolithiasis and short in cupulolithiasis. However, there are a few cases that do not fit in this general notion. Physiological factors, including volume, number, friction and viscosity of the otoconial debris, and velocity of the moving debris may well affect the latency of nystagmus. Horizontal nystagmus induced by an utricular disorder is another potential factor that may contribute to horizontal nystagmus of L-BPPV. The nystagmus pattern in L-BPPV is not simple, but sometimes complex, thus making its diagnosis difficult.
