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, wh ich 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), Whil e many typical features do not permit differentiation between BPPV and cPPV , for example, latency, course, and duration of nystagmus and vertigo durin g an attack, the direction of nystagmus often does. The nystagmus in BPPV a lways beats in the direction aligned to the affected semicircular canal pla ne, i.e., horizontal for the horizontal canal and vertical-torsional for th e vertical canals. Any other direction (paroxysmal torsional, upbeat, or do wnbeat nystagmus) indicates a central origin. Three cases of cPPV exhibitin g nystagmus in the latter directions are presented. In one of the cases wit h paroxysmal downbeat nystagmus and vertigo, all other parts of the neurolo gical examination and brain imaging initially showed no lesion in the poste rior fossa. The direction of nystagmus was the only sign that indicated a c entral origin.