[Benign paroxysmal positional vertigo : Typical and unusual clinical findings].

Benign paroxysmal positional vertigo (BPPV) is the most frequent form of vertigo seen in patients attending emergency departments. Leading symptoms are short attacks of vertigo provoked by head or body rotations. BPPV is caused by small calcium crystals, so-called otoconia, which are dislocated from the macula of the utricle mostly into the posterior semicircular canal. Free floating otoconia can move under the influence of gravity inside the semicircular canal (canalolithiasis) or adhere to the cupula (cupulolithiasis) causing displacement of the cupula. This results in positional nystagmus, whose directions and time courses are characteristic for the affected semicircular canal and the underlying cause. In recent years, however, a number of cases were reported, in which direction and times course of nystagmus differed from typical clinical findings. This may cause diagnostic problems.