Clinical characteristics and therapeutic outcomes of 120 patients with positional down-beat nystagmus (pDBN) with negative brain MRI.

OBJECTIVE: This study aims to observe the clinical characteristics, nystagmus features, and the effectiveness of repositioning maneuvers (RPM) in patients with pDBN and negative brain MRI. METHODS: We conducted a retrospective review of records pertaining to 3,083 vertigo patients, ultimately enrolling 120 of them (3.9%). Based on the characteristics of their nystagmus, these patients were classified into four categories: U-DBN (pDBN following upward beating nystagmus), S-DBN (single pDBN), Mix-BN (mixed beating nystagmus), and C-DBN (continuous pDBN). RESULTS: Most patients with U-DBN exhibited brief-latency (90.9%) transient nystagmus (100%), with a 100% effective rate for RPM (ipsilateral Epley maneuver). Most patients with S-DBN lacked a latent period for nystagmus onset (80.0%), with an comparable distribution of transient and persistent nystagmus (52.3% vs. 47.7%). The RPM is effective for S-DBN patients, with the contralateral Epley maneuver outperforming the ipsilateral one, with an efficacy rate of 100% versus 66.7-81.3%. Most patients with Mix-BN primarily exhibited transient nystagmus (84.4%) and responded well to RPM (ipsilateral Epley maneuver) with a 93.8% effective rate. In all patients with C-DBN, the nystagmus was persistent, and patients had poor treatment tolerance (treatment adherence rate of 48.3%) and a poor response to RPM (50.0% effective rate). During the RPM, 19 patients (15.8%) experienced changes in their nystagmus type, with an incidence rate higher than previously reported. CONCLUSION: Our findings suggest that MRI-negative pDBN is not uncommon in vertigo patients. U-DBN, S-DBN, and Mix-BN respond favorably to the Epley maneuver, suggesting a close association with benign paroxysmal positional vertigo (BPPV). However, C-DBN shows a suboptimal response to the Epley maneuver, with its underlying etiology still requiring further elucidation.