Pseudo-Spontaneous Nystagmus in Lateral Semicircular Canal Benign Paroxysmal Positional Vertigo

OBJECTIVES: Spontaneous nystagmus, which has been considered a typical sign of acute vestibulopathy, has recently been reported in benign paroxysmal positional vertigo involving the lateral semicircular canals (LC-BPPV) without unilateral vestibulopathy (pseudo-spontaneous nystagmus, PSN), but research about its clinical application is still limited. Here we investigate the frequency and characteristics of PSN in LC-BPPV patients, and estimate its prognostic value. METHODS: For 95 patients with LC-BPPV, we examined nystagmus in the sitting position in the clinic with video goggles. Patients were categorized as PSN or non-PSN, according to presence of horizontal nystagmus in the sitting position at diagnosis. The duration of vertiginous symptoms before diagnosis and the duration of treatment were compared between the two groups. The results of video-nystagmography test were reviewed when available. RESULTS: PSN was examined in 16 (16.8%) patients, all of whose symptoms disappeared immediately after successful repositioning therapy. While the duration of symptoms did not differ statistically between groups (P=0.481), the duration of treatment in the PSN group was significantly longer than in the non-PSN group (P<0.001). CONCLUSION: We conclude that the presence of spontaneous nystagmus in the sitting position does not preclude a diagnosis of LC-BPPV without unilateral vestibulopathy. PSN was related to a poor outcome of LC-BPPV in this study.