Pseudo-spontaneous nystagmus in patients with geotropic direction-changing positional nystagmus

BACKGROUND: Pseudo-spontaneous nystagmus has been reported in patients with direction-changing positional nystagmus (DCPN). Recently, the concept of a “light cupula” has been introduced as a pathophysiology that can exhibit persistent geotropic DCPN. Patients with persistent DCPN could have different characteristics of nystagmus. Therefore, we investigated the pseudo-spontaneous nystagmus in patients with transient (canalolithiasis) and persistent (belong to light cupula theory) geotropic DCPN. METHODS: In this study, prospectively, 49 patients with persistent geotropic DCPN and 67 patients with transient geotropic DCPN were enrolled. We compared the incidence of pseudo-spontaneous nystagmus between persistent and transient DCPN patients and characteristics of pseudo-spontaneous nystagmus and positional nystagmus by the head roll test in these patients. A prospective study was conducted at a dizziness clinic. RESULTS: Patients with persistent geotropic DCPN exhibited significantly higher incidence of pseudo-spontaneous nystagmus than patients with transient geotropic DCPN. Patients with transient DCPN showed a significantly higher mean SPV value during the head roll test than patients with persistent DCPN. All patients exhibiting pseudo-spontaneous nystagmus in patients with persistent DCPN had a null plane, and all patients had nystagmus beats to the opposite side of the null plane or the lesion side. CONCLUSION: Our results support the possibility that the mechanism between persistent and transient geotropic DCPN may be different. However, more studies are needed on the pathogenesis and mechanism of the two diseases, including the occurrence of pseudo-spontaneous nystagmus in the disease entity.