Caloric vertical nystagmus: the vertical semicircular canal in caloric testing.

Vertical nystagmus elicited by caloric testing does not necessarily mean there is central pathology. In a patient with confirmed peripheral vestibular disease, caloric stimulation produced an intense vertical nystagmus, which showed all the features of a caloric nystagmus. The patient had bilateral mastoid cavities, allowing easy stimulation of the posterior semicircular canal, using air. At the same time, a unilateral horizontal semicircular canal functional loss was observed, raising the possibility of dissociated canal dysfunction.