[Preliminary analysis of central paroxysmal positional vertigo]

Objective: To explore the possible pathogenesis of central paroxysmal positional vertigo (CPPV) by analyzing its clinical manifestations and characteristics. Methods: The clinical data of 3 patients with CPPV, including 1 male and 2 females, aged 36, 14 and 70 years old respectively, were collected from the Department of Otorhinolaryngology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences from June 2014 to June 2018. The clinical symptoms, nystagmus, other central ocular motor abnormalities, MRI, PET-CT, and laboratory findings were analyzed retrospectively. Results: All patients showed transient vertigo and nystagmus induced by head changes relative to gravity, but the characteristics of nystagmus did not conform to the typical characteristics of nystagmus in benign paroxysmal positional vertigo. None of patients response to repositioning maneuvers, and all patients presented with the signs of abnormal visual oculomotor system or other symptoms of central system. MRI, PET-CT and blood biochemical tests confirmed that the causes of CPPV in the patients were chronic hemorrhage, inflammation and paraneoplastic cerebellar degeneration. Although the etiology of the three cases is different, the lesion site is involved in the central velocity storage mechanism. Conclusion: The damage of central velocity storage mechanism may lead to the damage of feedback rotation signal correction pathway, and CPPV appears when the head position changes relative to gravity.

目的： 通过分析中枢性阵发性位置性眩晕（central paroxysmal positional vertigo，CPPV）的临床表现和特点探讨CPPV可能的发病机制。 方法： 收集2014年6月至2018年6月中国医学科学院北京协和医院收治的3例CPPV患者的临床资料，其中男性1例，女性2例，年龄分别为36、14、70岁。回顾性分析患者的临床症状、眼震特征、伴随的其他中枢眼动异常、MRI、正电子发射型计算机断层显像（PET-CT）及实验室检查结果。 结果： 所有患者在头部相对于重力变化时均表现出短暂的眩晕和诱发的眼震，但眼震的特点不符合良性阵发性位置性眩晕（benign paroxysmal positional vertigo，BPPV）眼震的典型特征。3例患者行复位治疗均无效，并且都伴有视眼动系统异常的体征或其他中枢系统症状。MRI、PET-CT、血生化结果证实了病因分别为慢性出血、炎症和副肿瘤小脑变性。3例患者虽病因不同但病变部位均涉及中枢速度存储机制（velocity storage mechanism，VSM）。 结论： VSM破坏，导致反馈性旋转信号修正通路受损，头位相对于重力发生变化时呈现CPPV的临床表现。.

Keywords: Benign paroxysmal positional vertigo; Central paroxysmal positional vertigo; Electronystagmography.