title: Paroxysmal positional vertigo syndrome.
abstract: BACKGROUND
  This study was initiated to investigate the differential diagnosis of patients with benign paroxysmal positional vertigo (BPPV) of different canals' origin.
  
  
  METHODS
  The eye movements of 292 patients were evaluated with the use of Frenzel glasses and infrared video cameras after positional tests. Epley's canal repositioning procedure (CRP) was conducted, with appropriate modifications for individual cases, on every patient.
  
  
  RESULTS
  Two different types of positional nystagmus were observed corresponding to the presence of otoliths in the lumen of each of the semicircular canals and on the cupola of the horizontal semicircular canal. The posterior canal was involved in 250 patients unilaterally and 23 patients bilaterally. The anterior canal variety was observed in four patients. In the horizontal canal, nine were of the cupulolithiasis and six of the canalithiasis variety. In seven patients. the affected canal converted to a different location. The canal repositioning procedure eliminated vertigo and abnormal eye movements in 88% of the unilateral posterior canal variety. The success rate of the procedure in the other varieties was 50%.
  
  
  CONCLUSIONS
  Positional vertigo can have characteristics corresponding to the presence of otolith particles in each of the semicircular canals. The treatment requires different strategies to move the otoliths, depending on their location in the vestibule.
authors.affiliation: Division of Head & Neck Surgery, University of California at Los Angeles School of Medicine, 90095-1624, USA.
authors.forename: V
authors.initials: V
authors.lastname: Honrubia
authors.forename: R W
authors.initials: RW
authors.lastname: Baloh
authors.forename: M R
authors.initials: MR
authors.lastname: Harris
authors.forename: K M
authors.initials: KM
authors.lastname: Jacobson
mesh_terms: D000368:Aged; D004576:Electromyography / Q000379:methods; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006257:Head / Q000502:physiology; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology; D009759:Nystagmus, Pathologic / Q000175:diagnosis; D012665:Semicircular Canals / Q000502:physiology; D013997:Time Factors; D014717:Vertigo / Q000175:diagnosis* / Q000503:physiopathology; D014722:Vestibule, Labyrinth / Q000503:physiopathology; D014741:Video Recording