title: The video Head Impulse Test (vHIT) detects vertical semicircular canal dysfunction.
abstract: BACKGROUND
  The video head impulse test (vHIT) is a useful clinical tool to detect semicircular canal dysfunction. However vHIT has hitherto been limited to measurement of horizontal canals, while scleral search coils have been the only accepted method to measure head impulses in vertical canals. The goal of this study was to determine whether vHIT can detect vertical semicircular canal dysfunction as identified by scleral search coil recordings.
  
  
  METHODS
  Small unpredictable head rotations were delivered by hand diagonally in the plane of the vertical semicircular canals while gaze was directed along the same plane. The planes were oriented along the left-anterior-right-posterior (LARP) canals and right-anterior-left-posterior (RALP) canals. Eye movements were recorded simultaneously in 2D with vHIT (250 Hz) and in 3D with search coils (1000 Hz). Twelve patients with unilateral, bilateral and individual semicircular canal dysfunction were tested and compared to seven normal subjects.
  
  
  RESULTS
  Simultaneous video and search coil recordings were closely comparable. Mean VOR gain difference measured with vHIT and search coils was 0.05 (SD = 0.14) for the LARP plane and -0.04 (SD = 0.14) for the RALP plane. The coefficient of determination R(2) was 0.98 for the LARP plane and 0.98 for the RALP plane and the results of the two methods were not significantly different. vHIT and search coil measures displayed comparable patterns of covert and overt catch-up saccades.
  
  
  CONCLUSIONS
  vHIT detects dysfunction of individual vertical semicircular canals in vestibular patients as accurately as scleral search coils. Unlike search coils, vHIT is non-invasive, easy to use and hence practical in clinics.
authors: Vestibular Research Laboratory, School of Psychology, University of Sydney, Sydney, Australia.
authors: Hamish Gavin
authors: HG
authors: Macdougall
authors: Leigh Andrew
authors: LA
authors: McGarvie
authors: Gabor Michael
authors: GM
authors: Halmagyi
authors: Ian Stewart
authors: IS
authors: Curthoys
authors: Konrad Peter
authors: KP
authors: Weber
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005133:Eye Movements; D005260:Female; D019416:Head Movements; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012044:Regression Analysis; D012665:Semicircular Canals / Q000503:physiopathology*; D015837:Vestibular Diseases / Q000175:diagnosis* / Q000503:physiopathology; D014741:Video Recording
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