Typical and atypical benign paroxysmal positional vertigo: literature review and new theoretical considerations.

Atypical variants of benign paroxysmal positional vertigo (BPPV) are often encountered and frequently confusing. The authors present a hypothetical framework that accounts for all classical patterns of BPPV and several unusual variants such as BPPV without nystagmus, BPPV with downbeat nystagmus and BPPV with paradoxically direction-changing nystagmus. The authors introduce new concepts, such as "ipsicanal switch" and "horizontal short arm canalolithiasis" and suggest that their use may improve diagnosis and treatment in everyday clinical practice. The possible consequences of saccular otoconia detachment are reviewed according to the literature.