Down-beating nystagmus in anterior canal benign paroxysmal positional vertigo.

Down-beating positional nystagmus is typically associated with central nervous system disease. Anterior canal benign paroxysmal positional vertigo (AC-BPPV) can mimic down-beating positional nystagmus of central origin, particularly when it is bilateral. Factors that increase the probability of bilateral AC-BPPV include a history of bilateral multicanal BPPV, transient down-beating and torsional nystagmus that follows the plane of the provoked canal, and the absence of co-occurring neurologic signs and symptoms of central nervous system dysfunction. With neurologic clearance for canalith repositioning, exploration for AC-BPPV and canalith repositioning trials may alleviate symptoms even when the nystagmus does not appear to fatigue. In the case presented, the use of a side-lying maneuver with the nose down to provoke AC-BPPV symptoms and the use of a reversed Epley to clear AC-BPPV symptoms are highlighted. This approach is helpful when the diagnosis is unclear and neck hyperextension is to be avoided.