Abstract

When doctors evaluate the complaints of dizziness, they often perform a series of clinical tests to look for evidence of a vestibular dysfunction. A useful procedure is to ask the patient to take 30 deep breaths and observe the gaze behind Frenzel goggles. If hyperventilation-induce nystagmus(HIN), this is evidence for an underlying vestibular imbalance. We studied a case of hyperventilation induced nystagmus patient. After hyperventilation, right horizontal nystagmus with Alexander law could be detected. By precisely measuring the HIN, we determined that inputs arising from the horizontal semicircular canal were mainly responsible. The ipsilaterality of the direction of the horizontal component of the nystagmus and the schwannoma site is debatable.