A case of persistent direction-changing positional nystagmus

of horizontal semicircular canal. In addition, there are rare cases of persistent direction-changing positional nystagmus, in which the nystagmus does not decay and is of long duration. The pathogenesis of this type of nystagmus is thought to involve a light cupula, because it is ex-plained by the deflection of the cupula in the antigravity direction, but the precise mechanism is still unknown. We encountered a case of vestibular Meniere’s disease with recurrent attacks of vertigo, in which the direction of nystagmus changed between the supine and prone posi-tions, and stopped at about 90 degrees below the left and right ears.