title: Hyperventilation-induced nystagmus in patients with vestibular schwannoma.
abstract: OBJECTIVE
  To analyze the nystagmus evoked by hyperventilation in patients with unilateral vestibular schwannoma and to use this information to predict the effects of hyperventilation on individual ampullary nerves.
  
  
  METHODS
  Three-dimensional scleral search coil eye movement recording techniques were used to record the magnitude and time course of eye movements in six patients with unilateral vestibular schwannoma and hyperventilation-induced nystagmus. The presenting complaints in five of these patients were vertigo or dysequilibrium.
  
  
  RESULTS
  The eye movement response to hyperventilation was a "recovery" nystagmus with slow-phase components corresponding to excitation of the affected vestibular nerve. Projection of the eye velocity vector into the plane of the semicircular canals revealed that fibers arising from the ampulla of the horizontal canal were most affected by hyperventilation with lesser activation of fibers to the superior canal and smaller, more variable responses from posterior canal fibers.
  
  
  CONCLUSIONS
  The three-dimensional characteristics of the nystagmus evoked by hyperventilation in patients with vestibular schwannoma provide insight into the vestibular end organs affected by the tumor and the mechanism responsible for the nystagmus. This finding indicates that hyperventilation resulted in a transient increase in activity from these partially demyelinated axons.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-0910, USA.
authors.forename: L B
authors.initials: LB
authors.lastname: Minor
authors.forename: T
authors.initials: T
authors.lastname: Haslwanter
authors.forename: D
authors.initials: D
authors.lastname: Straumann
authors.forename: D S
authors.initials: DS
authors.lastname: Zee
mesh_terms: D000328:Adult; D004292:Dominance, Cerebral / Q000502:physiology; D004584:Electronystagmography; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009464:Neuroma, Acoustic / Q000175:diagnosis* / Q000503:physiopathology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology; D012665:Semicircular Canals / Q000294:innervation; D014725:Vestibular Nerve / Q000503:physiopathology