ABSTRACT
Direction changing positional nystagmus (DCPN) is defined as a nystagmus that changes its direction with different head and body positions. In the past, it was usually thought that DCPN was the sign of central vestibular system lesion. But recently, there have been some reports that DCPN definitely does not localize the site of lesion in the central vestibular pathway, and that it more often indicates a peripheral vestibular site. However, congenital vestibular dys- or hypoplasia was not reported as a cause of DCPN. Recently, we experienced a 17-year-old patient who had a vestibular dys- or hypoplasia and showed a transient geotrophic DCPN with a normal cochlea. We report that congenital vestibular dys- or hypoplasia can be one of the causes of DCPN and present its possible mechanism.