title: Pseudo-anterior canalolithiasis.
abstract: CONCLUSIONS
  Because nystagmus induced by ampullopetal inhibition of the posterior semicircular canal (PSCC) rotates around the axis perpendicular to the plane of the anterior semicircular canal (ASCC) of the other side, when free-floating debris is initially located at the distal portion of the PSCC, a patient showing positional nystagmus appears to have the ASCC type of benign paroxysmal positional nystagmus. We name this 'pseudo-anterior canalolithiasis'.
  
  
  OBJECTIVE
  We report on pseudo-anterior canalolithiasis originating in the PSCC and discuss the differential findings between pseudo-anterior and true anterior canalolithiasis by means of three-dimensional (3D) analysis of the positional nystagmus.
  
  
  METHODS
  We performed 3D analysis of the positional nystagmus in a patient with true anterior canalolithiasis and in another patient with pseudo-anterior canalolithiasis.
  
  
  RESULTS
  In the patient with true anterior canalolithiasis, the direction of positional nystagmus during reverse Epley maneuver was constant and its axis was perpendicular to the plane of the right ASCC three-dimensionally. In contrast, in the patient with pseudo-anterior canalolithiasis, the first positional nystagmus of which the axis was perpendicular to the plane of the left ASCC became a second positional nystagmus of which the axis was perpendicular to the plane of the right PSCC during the reverse Epley maneuver.
authors.affiliation: Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, Osaka, Japan. imaitakao@hotmail.com
authors.forename: Takao
authors.initials: T
authors.lastname: Imai
authors.forename: Chisako
authors.initials: C
authors.lastname: Masumura
authors.forename: Noriaki
authors.initials: N
authors.lastname: Takeda
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kitahara
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Uno
authors.forename: Arata
authors.initials: A
authors.lastname: Horii
authors.forename: Suetaka
authors.initials: S
authors.lastname: Nishiike
authors.forename: Yumi
authors.initials: Y
authors.lastname: Ohta
authors.forename: Kayoko
authors.initials: K
authors.lastname: Shingai-Higashi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Morihana
authors.forename: Suzuyo
authors.initials: S
authors.lastname: Okazaki
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kamakura
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Takimoto
authors.forename: Hidenori
authors.initials: H
authors.lastname: Inohara
mesh_terms: D000328:Adult; D000368:Aged; D006801:Humans; D020347:Lithiasis / Q000150:complications*; D008297:Male; D009759:Nystagmus, Pathologic / Q000209:etiology* / Q000628:therapy; D012665:Semicircular Canals / Q000502:physiology*