title: Ocular vestibular evoked myogenic potentials: the effect of head and body tilt in the roll plane.
abstract: OBJECTIVE
  To explore effects of whole-head/body tilt in the roll plane on ocular-vestibular evoked myogenic potentials (oVEMP).
  
  
  METHODS
  Twenty healthy subjects were randomly tilted in an Eply Omniax rotator across a series of eight angles from 0° to 360° (at 45° separations) in the roll plane. At each position, oVEMPs to air-conducted (AC) and bone-conducted (BC) stimulation were recorded from unrectified infra-orbital surface electromyography during upward gaze. oVEMP amplitudes, latencies and amplitude asymmetry were compared across each angle of orientation.
  
  
  RESULTS
  Head orientation had a significant effect on oVEMP reflex amplitudes for both AC and BC stimulation (p<0.001). For both stimuli there was a trend for lower amplitudes with increasing angular departure from the upright position. Mean amplitudes decreased by 42.6-56.8% (AC) and 23.2-25.5% (BC) when tilted 180°. Roll-plane tilt had a significant effect on amplitude asymmetry ratios recorded in response to AC stimuli (p<0.001), indicating a trend for lower amplitudes from the dependent (down) ear. Amplitude asymmetry ratios for BC stimuli were unaffected by head and body orientation.
  
  
  CONCLUSIONS
  The results confirm an effect of head and body orientation on oVEMP reflexes recorded in response to air- and bone-conducted stimuli.
  
  
  CONCLUSIONS
  The upright position yields an optimal oVEMP response.
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, NSW, Australia.
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Taylor
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, NSW, Australia.
authors.forename: Minzhi
authors.initials: M
authors.lastname: Xing
authors.affiliation: Faculty of Health Sciences, University of Sydney, NSW, Australia.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Black
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, NSW, Australia.
authors.forename: G Michael
authors.initials: GM
authors.lastname: Halmagyi
authors.affiliation: Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Central Clinical School, University of Sydney, Sydney, NSW, Australia. Electronic address: miriam@icn.usyd.edu.au.
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Welgampola
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001844:Bone Conduction / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006257:Head; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D012027:Reflex, Vestibulo-Ocular; D058585:Vestibular Evoked Myogenic Potentials; D055815:Young Adult
keywords: Gravitational acceleration; Otolith organs; Static head tilt; oVEMP