title: Ocular vestibular evoked myogenic potentials: skull taps can cause a stimulus direction dependent double-peak.
abstract: OBJECTIVE
  To explore the mechanisms for skull tap induced ocular vestibular evoked myogenic potentials (oVEMP).
  
  
  METHODS
  An electro-mechanical "skull tapper" was used to test oVEMP in response to four different stimulus sites (forehead, occiput and above each ear) in healthy subjects (n=20) and in patients with unilateral loss of vestibular function (n=10).
  
  
  RESULTS
  In normals, the oVEMP in response to forehead taps and the contra-lateral oVEMP to taps above the ears were similar. These responses had typical oVEMP features, i.e. a short-latency negative peak (n10) followed by a positive peak (p15). In contrast, the ipsi-lateral oVEMP to the laterally directed skull taps, as well as the oVEMP to occiput taps, had an initial double negative peak (n10+n10b). In patients with unilateral loss of vestibular function, the crossed responses from the functioning labyrinth were very similar to the corresponding oVEMP in normals.
  
  
  CONCLUSIONS
  The present data support a theory that skull tapping may cause both a response that is more stimulus direction dependent and one that is less so.
  
  
  CONCLUSIONS
  Whereas the stimulus direction dependent occurrence of the negative double-peak might reveal the functional status of one part of the labyrinth, the rather stimulus direction-independent response might reveal the functional status of other parts.
authors.affiliation: Department of Otolaryngology, St. Olavs Hospital, Trondheim University Hospital, Norwegian University of Science and Technology, Trondheim, Norway. berit.holmeslet@stolav.no
authors.forename: Berit
authors.initials: B
authors.lastname: Holmeslet
authors.forename: Magnus
authors.initials: M
authors.lastname: Westin
authors.forename: Krister
authors.initials: K
authors.lastname: Brantberg
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology; D012886:Skull / Q000502:physiology*; D058585:Vestibular Evoked Myogenic Potentials / Q000502:physiology*; D014724:Vestibular Function Tests / Q000379:methods; D014732:Vibration; D055815:Young Adult