ABSTRACT
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.
ABSTRACT
OBJECTIVE: The purpose of the study is to prevent hearing loss when using intratympanic (IT) gentamicin for intractable Meniere's disease. MATERIALS AND METHODS: It is a retrospective case review study. Twenty five patients who had definite Meniere's disease and had either selective window application or weekly IT gentamicin were included into the study. First group (selective) had dexamethasone on the round window and gentamicin on oval window during exploratory tympanotomy procedure. The second group had IT gentamicin at weekly intervals. The degree of caloric weakness (CW), average hearing level in low pitch (HLP) (250, 500, 1000, 2000 Hz) and high pitch (HHP) (4000, 6000, 8000 Hz) were compared before and after treatment. The need for further treatment was noted. RESULTS: In the first group, the average HLP was increased from 51.6±7dB to 52.2±5.6 dB. The average HHP was increased 41.96±20.2 dB to 47.2±18.3 dB after treatment. The CW changed from 37.6±23.9 % to 54.6±30.6 %. In the second group, the average HLP was increased from 56.3±10.5 dB to 61.65±18.3 dB. The average HHP was increased 59.05±17.4 dB to 69.4±21.98 dB after treatment. The CW changed from 45.8±22.3% to 71.53±29.63 %. Both methods had statisticaly significant increase in caloric weakness. But only IT gentamicin led a significant hearing loss in HHP. CONCLUSION: The use of dexamethasone and gentamycin via different windows in the middle ear is safe and effective method for Meniere's disease in the short term. Application of dexamethasone protects not only the hearing cells but vestibular cells also.
