Posterior semicircular canal type benign paroxysmal positioning vertigo with ageotropic paroxysmal positioning nystagmus.

We report on 3 patients with typical benign paroxysmal positioning vertigo (BPPV) and atypical, paroxysmal positioning nystagmus. When the Dix-Hallpike test was performed, the patients exhibited an ageotropic nystagmus, different from that classically described in posterior semicircular canal BPPV. It was torsional-vertical with the vertical component beating downwards, and the torsional component was beating away from the lowermost ear. In both left and right Dix-Hallpike positions, the upper poles of the eyes were turning away from the lowermost ear. The atypical ageotropic paroxysmal positional nystagmus of the posterior semicircular canal was observed in the evolution of the BPPV in 2 patients and on the first examination in the third. Two patients had changing patterns of paroxysmal positioning nystagmus. Copyright 2001 S. Karger AG, Basel