Conversion between geotropic and apogeotropic persistent direction-changing positional nystagmus.

Conclusion: Clinical features in the course of conversion differed between patients with SSNHL and cupulopathy, which indicates that the pathophysiology of persistent geotropic or apogeotropic DCPN and the mechanism of the change in nystagmus direction may differ between the two groups.

Objective: The aim of this study is to investigate clinical characteristics of 10 patients with persistent DCPN who exhibited a conversion of nystagmus direction between geotropic and apogeotropic, and discuss possible mechanisms.

Methods: Using video-oculography, serial examinations of nystagmus in a head-roll test were performed.

Results: Of these 10 patients, five had sudden sensorineural hearing loss (SSNHL) and the remaining five had cupulopathy. In SSNHL, direction of nystagmus changed from geotropic to apogeotropic in three patients and from apogeotropic to geotropic in two patients. In cupulopathy, persistent apogeotropic DCPN always preceded persistent geotropic DCPN. The change in nystagmus direction occurred earlier in patients with cupulopathy (1 or 2 days after vertigo onset) than in patients with SSNHL (4-23 days after vertigo onset). While the null plane was consistently identified on one side, regardless of the nystagmus direction in cupulopathy, it was not always identified on the side of hearing loss in SSNHL.