Objective To analyze the characteristics of nystagmus during the Dix-Hallpike and Roll tests in patients with benign paroxysmal positional vertigo (BPPV) using three-dimensional videonystagmography (3D-VNG), in order to to optimize diagnostic and therapeutic strategies of BPPV.

Methods A retrospective analysis was conducted on 68 patients with posterior semicircular canal (PSC)-BPPV and 26 patients with horizontal semicircular canal (HSC)-BPPV. Nystagmus data obtained from 3D-VNG were reviewed for all patients, with a focus on the eye movement components during the Dix-Hallpike test in PSC-BPPV patients and the Roll test in HSC-BPPV patients. The direction and reversal rates of the vertical, horizontal, and torsional components were recorded and analyzed.

Results All PSC-BPPV patients exhibited highly consistent three-dimensional nystagmus characteristics during the Dix-Hallpike test: vertical nystagmus was uniformly upward, torsional nystagmus was predominantly clockwise in left-side BPPV patients (17/23) and counterclockwise in right-side BPPV patients (44/45), while the horizontal component was mostly directed contralaterally (50/68); upon transitioning from the head-hanging to the sit-up position, vertical nystagmus components in all patients reversed, and torsional and horizontal nystagmus components reversed in approximately 50.0% or more patients. Among HSC-BPPV patients, right-side BPPV patients all showed right-beating (geotropic) horizontal nystagmus with predominantly upward vertical component (16/19), while most left-side BPPV patients showed left-beating horizontal nystagmus (6/7) with predominantly downward vertical component (6/7). During head rotation toward the healthy side, most (25/26) HSC-BPPV patients exhibited a reversal in the horizontal nystagmus direction, reduced intensity compared to the affected side, with a reversal in vertical components in 3 patients, and atypical torsional components.

Conclusions 3D-VNG could precisely quantitative analyze three-dimensional features of nystagmus in BPPV patients, improve diagnostic accuracy in canal and side localization, particularly in PSC-BPPV patients.