Air caloric stimulation with tympanic membrane perforation.

Warm air caloric stimulation in an ear with tympanic membrane perforation or mastoidectomy cavity often causes contralateral nystagmus. Secondary nystagmus is common. Our evidence with squirrel monkeys and patients indicates that the primary "inversion" results from endolymph cooling due to evaporative cooling due to evaporative cooling of the mucus lining the middle ear cavity, by the dry air stimulus. Disconjugate horizontal nystagmus was found in a patient with large eardrum perforation, after cold air caloric stimulation. The effect probably resulted from stimulation of the anterior or posterior vertical semicircular canal. Inverted or disconjugate caloric nystagmus after air stimulation is much more frequently due to tympanic membrane perforation, or moisture in the external ear, than to central nervous system disease.