Atypical posterior canal benign paroxysmal positional vertigo mimicking anterior canal involvement: a case series and review of the literature.

backgroundBenign paroxysmal positional vertigo most commonly affects the posterior semicircular canal, producing upbeat-torsional nystagmus during positional testing. An apogeotropic variant of posterior semicircular canal benign paroxysmal positional vertigo may present with downbeat-torsional nystagmus, thereby mimicking anterior canal benign paroxysmal positional vertigo and potentially leading to misdiagnosis. CASE PRESENTATION: We report a case series of 14 patients (mean age 56.2 years; 10 females, 4 males; all of Kosovar ethnicity) presenting with positional downbeat nystagmus suggestive of anterior canal benign paroxysmal positional vertigo. All patients underwent video-oculography-assisted Dix-Hallpike and straight head-hanging tests. Nine patients (64%) demonstrated transformation to classic posterior semicircular canal benign paroxysmal positional vertigo nystagmus after initial repositioning maneuvers, indicating atypical posterior semicircular canal involvement. Transformation occurred after a mean of 4.2 days. All transformed cases resolved following the Epley maneuver. Two patients with persistent anterior canal benign paroxysmal positional vertigo required repeated Yacovino maneuvers. Recurrence occurred in four patients (28%) within 6 months and was successfully managed with repeat treatment. In this small observational series, adjunctive betahistine therapy was not associated with a statistically significant reduction in recurrence; however, conclusions regarding pharmacologic efficacy are limited by sample size.

conclusionAtypical posterior semicircular canal benign paroxysmal positional vertigo can closely mimic anterior canal benign paroxysmal positional vertigo. Recognition of nystagmus transformation following repositioning maneuvers, supported by video-oculography, is essential for accurate diagnosis and optimal management.