VESTIBULAR DISEASE UNMASKED BY HYPERVENTILATION

Hyperventilation-induced dizziness is off;ena thought to be psychogeni c, but its effects in the presence of known vestibular disease have no t been adequately examined. In this study hyperventilation was tested in two models of vestibular disease, These were, first, patients with profound unilateral vestibular deficit (prior translabyrinthine acoust ic neuroma resection [postsurgery group]) and, second, patients with v ariable unilateral vestibular deficit (unoperated unilateral acoustic neuroma [presurgery group]), Patients were hyperventilated for 90 seco nds, Using infrared videonystagmography, 100% of the 32 postsurgery pa tients and 82% of the 28 presurgery patients developed nystagmus with hyperventilation. Hyperventilation was more sensitive than head shake for eliciting nystagmus in these models. The false-positive rate for n ystagmus in 29 normal volunteers was 3.5% for hyperventilation and 10% far head shake, Our results show that hyperventilation can unmask und erlying vestibular disease.