Conversion between geotropic and apogeotropic persistent direction-changing positional nystagmus

<i>Conclusion:</i> 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. <i>Objective:</i> 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. <i>Methods:</i> Using video-oculography, serial examinations of nystagmus in a head-roll test were performed. <i>Results:</i> 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.

结论： 突发性感音神经性耳聋（sudden sensorineural hearing loss, SSNHL）患者与壶腹顶病变（cupulopathy）患者在病程转换阶段的临床特征存在差异，这提示两组患者的持续性向地性或离地性变向性位置性眼震（direction-changing positional nystagmus, DCPN）的病理生理学机制，以及眼震方向改变的潜在机制均存在不同。
目的： 本研究旨在调查10例眼震方向可在向地性与离地性之间转换的持续性变向性位置性眼震患者的临床特征，并探讨其可能的发病机制。
方法： 采用视频眼震图（video-oculography, VOG）对滚转试验中的眼震进行系列检查。
结果： 10例患者中，5例为突发性感音神经性耳聋（SSNHL），剩余5例为壶腹顶病变。在SSNHL患者中，3例眼震方向由向地性转换为离地性，2例由离地性转换为向地性。在壶腹顶病变患者中，持续性离地性变向性位置性眼震始终先于持续性向地性变向性位置性眼震出现。壶腹顶病变患者的眼震方向转换发生时间（眩晕发作后1或2天）早于SSNHL患者（眩晕发作后4~23天）。无论壶腹顶病变患者的眼震方向如何，其零平面始终固定于单侧；而SSNHL患者的零平面并不总是与听力受损侧一致。