TYMPANIC MEMBRANE DISPLACEMENT ANALYSIS AFTER GLYCEROL INTAKE - EFFECTS ON INTRACRANIAL AND INTRACOCHLEAR FLUID PRESSURE

Background: Intracranial pressure is transmitted to the perilymph of t he cochlea via the cochlear aqueduct and to the endolymph via Reissner 's membrane. The tympanic membrane displacement analyzer (TDA) is a ne w system that may provide a useful, noninvasive, indirect method to id entify intracranial and intracochlear pressure changes. Methods: We pe rformed measurements in 20 persons with normal hearing and in 29 patie nts with various unilateral dis eases of the inner ear such as sudden hearing loss or Meniere's disease. Another series of measurements were done in 15 normal-hearing persons and in 15 patients with Meniere's d isease before and after oral ingestion of glycerol. Results: In the fi rst series of measurements, no significant differences in the tympanic membrane displacement were found between normal-hearing individuals a nd patients with unilateral diseases of the inner ear. In the second s eries, in all individuals a temporary, relative decrease in intracochl ear pressure was found after oral ingestion of glycerol but without an y significant difference between the two groups. Conclusions: These re sults revealed that the TDA is apparently not useful in the evaluation of patients having Meniere's disease.