Abstract
Benign paroxysmal positional vertigo (BPPV), one of the most common diseases of peripheral vestibular origin, is characterized by transient vertigo accompanied by benign paroxysmal positional nystagmus (BPPN) provoked by turning over in bed, lying down or sitting up. BPPN with a torsional component, short latency and a crescendo-decrescendo mode, is provoked by positional testing and disappears within 30 sec. The direction of the torsional nystagmus, provoked by lying down, reverses by sitting up. The nystagmus may decrease by repeated provocations as an adaptation. Canalolithiasis of the posterior canal is widely accepted as a cause of BPPV, because BPPN is well predicted and BPPV is successfully treated by Epley's canalith repositioning procedure on the basis of this hypothesis. Canalolithiasis of both the horizontal and anterior canals has also been reported as BPPV-variants. In this study, BPPN recorded by an infrared CCD camera and video recorder, and the incidence and meaning of the vertical component of BPPN were investigated in 110 cases of BPPV with torsional BPPN. Out of all 110 cases, up beating vertical component appeared in 39 (35.5%), down beating in 24 (21.8%) and no vertical component in 47 cases (42.7%), when torsional BPPN was provoked by lying down. Horizontal nystagmus of the direction changing type was also observed in 4 cases. According to the canalolithiasis hypothesis, upward and downward vertical components triggered by lying down should occur in the posterior and anterior canal types, respectively. Pure torsional positional nystagmus provoked by positioning was assumed to occur in the crus communis type, in which free-floating endolymph particles remain in the crus communis of the labyrinth.
