Development of a new maneuver to rapidly restore positional nystagmus from benign paroxysmal positional vertigo fatigue in patients with posterior canal-type benign paroxysmal positional vertigo: a single-arm prospective interventional clinical trial.

Purpose: Posterior canal-type benign paroxysmal positional vertigo (pc-BPPV) is diagnosed when positional torsional nystagmus is induced by the Dix-Hallpike test (DHT). When the DHT is repeated, positional nystagmus disappears. This phenomenon is known as BPPV fatigue. In cases where positional nystagmus cannot be induced by the DHT because of BPPV fatigue occurring just before a medical examination, or where positional nystagmus is not observed during the first DHT, we cannot make a diagnosis of pc-BPPV because the DHT can no longer induce the positional nystagmus typical of pc-BPPV. Therefore, this study aimed to develop a new maneuver to rapidly restore positional nystagmus in cases of BPPV fatigue, thereby facilitating accurate diagnosis.

Methods: Twenty patients with pc-BPPV performed the DHT twice to induce BPPV fatigue, with the new maneuver being used, and then performed a third DHT to verify the restoration of positional nystagmus. The primary outcome measure (POM) was the ratio between the maximum slow-phase eye velocity of positional nystagmus during the third DHT and that during the first DHT. A higher ratio indicates a greater ability of the new maneuver to restore nystagmus.

Results: The 95% confidence interval for the POM was 0.712-1.026, exceeding the pre-defined lower limit of efficacy of 0.7 specified in the protocol.

Conclusion: The high values for the POM suggest that the new maneuver successfully restores positional nystagmus and demonstrates its potential applicability in clinical practice for diagnosing pc-BPPV in cases complicated by BPPV fatigue.