Clinical Characteristics of Benign Paroxysmal Positional Vertigo Positive on Bilateral Dix-Hallpike Test

Objectives: The purpose of this study is to investigate the clinical characteristics of benign paroxysmal positional vertigo (BPPV) which showed torsional nystagmus on bilateral Dix-Hallpike test, and to analyze the clinical features of pseudo-bilateral BPPV.Methods: This study is a retrospective chart review of a total of 341 patients diagnosed with BPPV of posterior canal (PC-BPPV). Among them, patients who showed torsional nystagmus on bilateral Dix-Hallpike test were defined as “bilateral DixHallpike positive patients,” who were classified into true- and pseudo-bilateral PC-BPPV group through analysis of nystagmus direction. And pseudo-bilateral PC-BPPV were categorized into two subtypes according to their pathomechanisms. Clinical characteristics including sex, age, underlying vestibular disorders, recurrence and the number of Epley maneuvers were analyzed. Student t-test and Mann-Whitney U-test were used for statistical analysis.Results: Among 341 patients, 27 patients (7.9%) were “bilateral Dix-Hallpike positive patients”. They received more Epley maneuvers than the group of unilateral PC-BPPV until the resolution of nystagmus (2.3 vs. 1.4, p＜0.001). Fifteen patients out of 27 were diagnosed with pseudo-bilateral PC-BPPV, who were classified into two subtypes according to their pathomechanisms. The number of Epley maneuvers was not different between true- and pseudo-bilateral PC-BPPV.Conclusions: Patients with pseudo-bilateral PC-BPPV were common among “bilateral Dix-Hallpike positive patients.” For their better treatment, understanding of possible pathophysiology, accurate Dix-Hallpike test and detailed analysis of nystagmus direction are necessary.