title: Prevalence and Characteristics of Positional Nystagmus in Normal Subjects.
abstract: In clinical practice, patients are often referred due to a finding of positional nystagmus that does not always appear to correlate with clinical symptoms of benign paroxysmal positional vertigo. To know when to consider nystagmus to be of clinical relevance, it is necessary to know the prevalence and characteristics of positional nystagmus in a healthy population.
  
  
  
  Case series of 75 healthy subjects.
  
  
  
  Two tertiary referral centers in Norway.
  
  
  
  Seventy-five adult subjects aged 40 ± 13 years (mean ± SD; range, 21-87) without a history of vertigo or balance disorder were included from 2013 to 2015. The subjects underwent 6 different standardized positional tests in a repositioning chair. Videonystagmography was used to record eye movements. Of 1350 recordings, 1329 were included and analyzed.
  
  
  
  Positional nystagmus was detected in 88% of the subjects. The most common finding was nystagmus in the Dix-Hallpike position, which occurred in 55% of the subjects. The 95th percentile of the maximum slow-phase velocity for each subject was found to be 5.06° per second (n = 54) in the horizontal plane and 6.48° per second (n = 48) in the vertical plane.
  
  
  
  Positional nystagmus is a common finding in normal subjects and occurred in 88% of the healthy subjects in the present study. Horizontal direction-changing apogeotropic or geotropic nystagmus may occur in asymptomatic subjects. However, nystagmus that is of the paroxysmal type or has a slow-phase velocity greater than approximately 5° per second in the horizontal plane or 6.5° per second in the vertical plane should be considered outside the 95th percentile.
authors.affiliation: National Competence Service for Vestibular Disorders, Department of Otorhinolaryngology, Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway camillamartens@gmail.com.
authors.forename: Camilla
authors.initials: C
authors.lastname: Martens
authors.affiliation: National Competence Service for Vestibular Disorders, Department of Otorhinolaryngology, Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway.
authors.forename: Frederik Kragerud
authors.initials: FK
authors.lastname: Goplen
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, Oslo University Hospital, Oslo, Norway.
authors.forename: Karl Fredrik
authors.initials: KF
authors.lastname: Nordfalk
authors.affiliation: National Competence Service for Vestibular Disorders, Department of Otorhinolaryngology, Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway.
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Aasen
authors.affiliation: National Competence Service for Vestibular Disorders, Department of Otorhinolaryngology, Head and Neck Surgery, Haukeland University Hospital, Bergen, Norway Department of Clinical Medicine, University of Bergen, Bergen, Norway.
authors.forename: Stein Helge Glad
authors.initials: SH
authors.lastname: Nordahl
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D065635:Benign Paroxysmal Positional Vertigo / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D009760:Nystagmus, Physiologic / Q000502:physiology*; D015995:Prevalence; D014724:Vestibular Function Tests
keywords: normal population; positional nystagmus; rotational chair; videonystagmography