title: Age dependent normal horizontal VOR gain of head impulse test as measured with video-oculography.
abstract: BACKGROUND
  The head impulse test (HIT) is a recognised clinical sign of the high frequency vestibulo-ocular reflex (VOR), which can be quantified with video-oculography. This measures the VOR gain as the ratio of angular eye velocity to angular head velocity. Although normative data is available for VOR gain with video-oculography, most normal studies in general include small numbers of subjects and do not include analysis of variation of VOR gain with age. The purpose of our study was to establish normative data across 60 control subjects aged 20 to 80 years to represent a population distribution.
  
  
  METHODS
  Sixty control subjects without any current or previous form of brain disorder or vertigo participated in this study and form the basis for future comparison to patients with vestibular lesions. The relationship between the horizontal vestibulo-ocular reflex (HVOR) velocity gain and age was analysed using a mixed regression model with a random effect for subjects. Differences in testing technique were assessed to ensure reliability in results.
  
  
  RESULTS
  The mean HVOR velocity gain of 60 normal subjects was 0.97 (SD = 0.09) at 80 ms and 0.94 (SD = 0.10) at 60 ms. The 2 SD lower limit of normal HVOR velocity gain was 0.79 at 80 ms and 0.75 at 60 ms. No HVOR velocity gain fell below 0.76 and 0.65 at 80 ms and 60 ms respectively. The HVOR velocity gain declined by 0.012 and 0.017 per decade as age increased at 80 ms and 60 ms respectively. A non-physiologically high horizontal HVOR velocity gain was found to occur in tests where passive HITs were predictable in direction and time and where target distance was below 0.70 m.
  
  
  CONCLUSIONS
  Normative data with respect to HVOR velocity gain decreases slightly with age, but with careful attention to methodology the 2 SD lower limit of normal is relatively robust across a wide age range and into the eighth decade, without requirement for adjustment with age.
authors.affiliation: Department of Neurology, Wellington Hospital, Riddiford Street, Private Bag 7902, Wellington South, Wellington, New Zealand.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Mossman
authors.affiliation: Department of Neurology, Wellington Hospital, Riddiford Street, Private Bag 7902, Wellington South, Wellington, New Zealand. stuart.mossman@ccdhb.org.nz.
authors.forename: Stuart
authors.initials: S
authors.lastname: Mossman
authors.affiliation: Dean's Department, University of Otago, Wellington, New Zealand.
authors.forename: Gordon
authors.initials: G
authors.lastname: Purdie
authors.affiliation: Institute of Medical Technology, Brandenburg University of Technology Cottbus, Senftenberg, Germany.
authors.forename: Erich
authors.initials: E
authors.lastname: Schneider
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004585:Electrooculography; D005260:Female; D064087:Head Impulse Test; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D015837:Vestibular Diseases / Q000175:diagnosis / Q000503:physiopathology; D014741:Video Recording; D055815:Young Adult