Detecting Intralabyrinthine Pressure Increase by Postural Manipulation with Wideband Tympanometry and Distortion Product Otoacoustic Emissions.

OBJECTIVE: Intracranial pressure increase is known to affect inner ear pressure through the cochlear and vestibular aqueducts. This finding forms a good model for inner ear pressure studies. Standard techniques used to detect this pressure increase are neither reliable nor easily repeatable or cheap. Studies with immitancemetry and otoacoustic emissions have been giving hopeful results. This study aims to confirm the results in the literature with wideband tympanometry and add a new parameter of otoacoustic emissions to inner ear pressure testing. METHODS: Wideband tympanometry (WBT) and distortion product otoacoustic emissions (DPOAE) tests were applied to 40 healthy participants in sitting, supine, and Trendelenburg positions. DPOAE were measured under ambient or peak pressure. Resonance frequency, tympanic peak pressure, 1000, 1500, 2000, 3000, 4000, and 6000 Hz frequencies in DPOAE were measured. RESULTS: The increase in the tympanic peak pressure and the decrease in resonance frequency (RF) due to position change were found statistically significant (p<0.01). Signal noise ratio (SNR) decrease at 1 kHz frequency and SNR increase at 2, 3, 6 kHz in the normal protocol, SNR decrease at 1 kHz in the pressurized protocol were found statistically significant (p<0.01). CONCLUSION: RF in WBT and 1 kHz DPOAE SNR parameters were found useful in supporting the diagnosis in pathologies that increase intracranial pressure and inner ear pressure. Future research may ease their widespread use in clinical practice as they are non-invasive and rapidly applicable.

Preliminary Results of a New Experimental Model for Intratympanic Treatment.

OBJECTIVE: Corticosteroids have been applied via transtympanic route for a long time to treat the inner ear disorders. A few animal models were used to answer the questions, "How much drug goes into the inner ear?" and "How far does the drug reach through the scala tympani and/or scala vestibuli?" However, the cerebrospinal fluid contamination poses a major problem. The aims of this study were to create a new sampling model showing the dexamethasone distribution in the inner ear and to provide more reliable data about drug concentrations. METHODS: Ten Hartley strain albino guinea pigs that weighted between 400 and 600 g were used. After dexamethasone application to the left ear, they were sacrificed at two time points: after 0.5 hours (Exp 1) and after 2 hours (Exp 2). The temporal bones were immediately dissected and put into liquid nitrogen for freezing. The apex, second turn, and basal turns of the cochlea and vestibule were separated, while the bone was in the frozen state. The samples were prepared and measured with ultraviolet (UV) spectroscopy. RESULTS: The total amount of dexamethasone was statistically higher in the left ear than the control ear. Although the basal turn and vestibule were the most prominent parts, there was no statistical difference between the different parts of the inner ear at 0.5 hours. The vestibule and the apex showed the highest level of dexamethasone at 2 hours. CONCLUSION: Although the model has some limitations, it can measure dexamethasone concentrations and show the time variability in the inner ear.