title: Unilateral mimicking bilateral benign paroxysmal positioning vertigo.
abstract: BACKGROUND
  Unilateral benign paroxysmal positioning vertigo (BPPV) may mimic bilateral BPPV if the diagnostic positioning maneuver is executed without appropriate alignment of the head and neck with the trunk.
  
  
  METHODS
  Appropriate alignment is achieved by adjusting the plane of the affected posterior semicircular canal so that it is parallel to the plane of diagnostic head tilt, ie, 45 degrees horizontal head rotation to the left before a head tilt to the right in suspected right-sided BPPV. With inappropriate head alignment and head tilt to the side of the unaffected ear, a free-floating clot within the long arm of the uppermost posterior canal may gravitate toward the cupula and become settled on it. This causes ampullopetal cupulolithiasis, evoking geotropic nystagmus, which may mimic BPPV of the unaffected ear.
  
  
  CONCLUSIONS
  This hypothesis explains the seemingly paradoxical observation of immediate relief from "bilateral BPPV" following unilateral surgical canal occlusion on the "more symptomatic" side.
authors.affiliation: Department of Neurology, Klinikum Grosshadern, University of Munich, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Steddin
authors.forename: T
authors.initials: T
authors.lastname: Brandt
mesh_terms: D002137:Calculi / Q000150:complications*; D015834:Cochlear Diseases / Q000150:complications*; D003937:Diagnosis, Differential; D006257:Head; D006801:Humans; D009333:Neck; D010808:Physical Examination / Q000379:methods*; D011187:Posture; D012399:Rotation; D014717:Vertigo / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology