title: Spontaneous inversion of nystagmus without a positional change in the horizontal canal variant of benign paroxysmal positional vertigo.
abstract: OBJECTIVE
  We investigated the neuro-otological findings, including nystagmus, and the clinical course of patients with the horizontal canal variant of benign paroxysmal positional vertigo (HC-BPPV), who showed spontaneous inversion of nystagmus without a positional change. Furthermore, we speculated on the possible mechanism of spontaneous inversion of nystagmus without a positional change.
  
  
  METHODS
  The characteristics of spontaneous inversion of positional nystagmus without a positional change were analyzed in 7 patients with HC-BPPV.
  
  
  RESULTS
  All patients were diagnosed as having HC-BPPV. During the positional test, the spontaneous inversion of nystagmus was observed in the same head position in all patients. Spontaneous inversion was observed on both sides in 5 patients, and only on 1 side in 2 patients. All patients presented with geotropic nystagmus in the first phase, and ageotropic nystagmus in the second phase.
  
  
  CONCLUSIONS
  The coexistence of cupulolithiasis and canalolithiasis appears to be a possible mechanism of the spontaneous inversion of positional nystagmus.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Akihide
authors.initials: A
authors.lastname: Ichimura
authors.forename: Koji
authors.initials: K
authors.lastname: Otsuka
authors.forename: Akira
authors.initials: A
authors.lastname: Hagiwara
authors.forename: Taro
authors.initials: T
authors.lastname: Inagaki
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Shimizu
authors.forename: Noriko
authors.initials: N
authors.lastname: Nagai
authors.forename: Shigeto
authors.initials: S
authors.lastname: Itani
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D065635:Benign Paroxysmal Positional Vertigo / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications; D007759:Labyrinth Diseases / Q000473:pathology; D020347:Lithiasis / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy; D009760:Nystagmus, Physiologic; D012665:Semicircular Canals / Q000473:pathology / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000150:complications; D014724:Vestibular Function Tests
keywords: Horizontal canal BPPV; benign paroxysmal vertigo; lateral canal BPPV; positional nystagmus