The direction of nystagmus is important for the diagnosis of central paroxysmal positioning nystagmus (cPPV)

Head-positioning maneuvers can lead to paroxysmal nystagmus and vertigo, which are usually due to a peripheral vestibular disorder like, for example, benign paroxysmal positioning vertigo (BPPV), They are less commonly caused by a central lesion (central paroxysmal positioning nystagmus, cPPV), While many typical features do not permit differentiation between BPPV and cPPV, for example, latency, course, and duration of nystagmus and vertigo during an attack, the direction of nystagmus often does. The nystagmus in BPPV always beats in the direction aligned to the affected semicircular canal plane, i.e., horizontal for the horizontal canal and vertical-torsional for the vertical canals. Any other direction (paroxysmal torsional, upbeat, or downbeat nystagmus) indicates a central origin. Three cases of cPPV exhibiting nystagmus in the latter directions are presented. In one of the cases with paroxysmal downbeat nystagmus and vertigo, all other parts of the neurological examination and brain imaging initially showed no lesion in the posterior fossa. The direction of nystagmus was the only sign that indicated a central origin.