Upright positioning-related reverse nystagmus in posterior canal benign paroxysmal positional vertigo and its effect on prognosis.

BACKGROUND Positional nystagmus elicited by the Dix-Hallpike maneuver often reverses its direction as the patient is re-seated from the provoking head hanging position. The incidence of reverse nystagmus and its association with prognosis in posterior canal benign paroxysmal positional vertigo (pcBPPV) is not clear. OBJECTIVE To determine the incidence of upright positioning-related reverse nystagmus and its association with the success of canalith repositioning (Epley) maneuver (CRM) treatment in pcBPPV. METHODS The records of patients that had been tested with video-nystagmographyin a tertiary care center, between October 2016 and March 2019, were reviewed. Data were obtained from detailed analysis of video recordings of 321 patients with typical pcBPPV. RESULTS Reverse nystagmus was determined in 85% of the patients with pcBPPV. The number of CRMs required for treatment was lower in patients with reverse nystagmus (1.32±0.68) compared to patients without reverse nystagmus (1.81±0.98) (p < 0.001). There was not a statistically significant relationship between reverse nystagmus and recurrence (p = 0.623). CONCLUSIONS The absence of reverse nystagmus on upright positioning during the Dix-Hallpike test predicts poor success for the CRM, as repetitive repositioning maneuvers might be required to achieve successful treatment in pcBPPV.