Periodic alternating nystagmus in Meniere's disease: the peripheral type?

Periodic alternating nystagmus (PAN) is a spontaneous horizontal nystagmus that reverses direction periodically. PAN has been reported in acquired and congenital forms. The lesion site of the acquired form of PAN has been attributed to the caudal brainstem or cerebellum. We report an extremely rare case (a 59-year-old woman) with bilateral Meniere's disease, who presented PAN. PAN in this patient was suppressed in the light. This patient had smooth pursuit and normal optokinetic nystagmus, although patients with PAN usually show saccadic pursuit and impaired optokinetic nystagmus. These findings were different features from those of the central or congenital form of PAN. It should be kept in mind that peripheral vestibular disorders such as Meniere's disease could produce PAN.