Incidence of unilateral and bilateral benign paroxysmal positional vertigo when the left and right Dix-Hallpike manoeuvres are positive: a model based on the sense of torsional nystagmus

Patients presenting with nystagmus indicative of benign paroxysmal positional vertigo (BPPV) during the left and the right Dix-Hallpike manoeuvres (DHMs) are frequently seen in clinical practice. In such cases, BPPV may be unilateral or bilateral. The aim of this study is to describe the incidence of unilateral and bilateral BPPV when both DHMs are positive, taking into account the sense of the torsional component of nystagmus. This is a prospective multicentre study. BPPV patients were classified into three groups: patients with only one positive DHM (control group, CG), patients showing positive bilateral DHM with nystagmus in the same sense in both DHMs (same sense group, SSG) and patients showing positive bilateral DHM with the torsional component of nystagmus beating in opposite senses in each DHM (opposite sense group, OSG). Only one Epley Manoeuvre (EM) was performed on all patients. Based on the ipsilateral result of the EM, the contralateral result of the same EM and the BPPV resolution rate in the control group, a model was developed to predict the incidence of unilateral and bilateral BPPV in the SSG and the OSG. There were 234 patients in the control group, 20 in the SSG and 23 in the OSG. The model estimated that the percentage of unilateral BPPV would be 89.5% in SSG and 38.7% in OSG. Using these findings, we conclude that when both DHMs are positive, BPPV may be unilateral or bilateral. If the torsional components of both nystagmuses beat in the same sense, it is more likely to be unilateral BPPV. If the torsional components beat in opposite senses, both situations can be considered equally likely.