[Pathological localization of benign paroxysmal positional vertigo--from three-dimensional analysis of nystagmus]

Although it has been speculated that benign paroxysmal positional vertigo (BPPV) derives from the utricle or posterior semicircular canal, the origin of BPPV is still controversial. In this study, we investigated the role of the utricle and semicircular canals (especially the vertical semicircular canal) relative to BPPV by three-dimensional analysis, focusing on the horizontal, vertical, and torsional positions by applying our computerized eye movement analysis system. In 13 subjects who were diagnosed as having BPPV, we carried out the positioning nystagmus tests, and analyzed three components of nystagmus. By using a pendular rotation stimulus, we also measured three components of eye movement elicited from the vertical semicircular canals in 5 normal subjects and 2 subjects from whom acoustic tumors were removed by the translabyrinthine approach. We compared two components (vertical and torsional) of BPPV with those of eye movements elicited from the vertical semicircular canals. In BPPV, the slow phase velocity of the torsional component was greater than that of the vertical component. Conversely, the amplitude of the vertical component from the vertical semicircular canals was greater than that of the torsional component. From these results, by analyzing the vestibuloocular reflex of vertical semicircular canals, it is difficult to support the idea that the pathology of BPPV is located in the posterior semicircular canal alone.