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Hydrocortisone applied into the round window niche causes electrophysiological dysfunction of the inner ear
O Spandow1, M Anniko, S Hellström
1Department of Oto-Rhino-Laryngology and Head and Neck Surgery, University Hospital, Umeå, Sweden.
Abstract:
A suspension of 2% hydrocortisone, micronized in sterile water, was instilled through a perforation in the tympanic membrane into the round window (RW) niche of 9 healthy rats once a day for 5 consecutive days. Three animals were used as controls, and were exposed to sterile water only instilled into the RW niche. Auditory brainstem response (ABR) thresholds were determined for eight frequencies: 2, 4, 6, 8, 12, 16, 20 and 31.5 kHz. Hydrocortisone caused impaired ABR thresholds in the frequency range of 12-31.5 kHz after 5 days of instillation. The impaired thresholds remained unchanged for 2 months, indicating irreversible electrophysiological changes in the inner ear. No morphological damage could be detected in the cochlea by means of light microscopy or transmission electron microscopy. However, hydrocortisone delayed the healing of the perforated tympanic membrane.
Insights
Instilling hydrocortisone into the inner ear of rats caused irreversible hearing loss at high frequencies. This study highlights potential risks of topical corticosteroids on auditory function and tympanic membrane healing.
Area of Science:
- Ototoxicology
- Neuroscience
- Pharmacology
Background:
- Topical corticosteroids are used for inner ear conditions.
- Potential ototoxicity of hydrocortisone requires investigation.
- Effects on auditory function and cochlear integrity are not fully understood.
Purpose of the Study:
- To evaluate the effects of hydrocortisone instillation on auditory function and cochlear morphology.
- To determine if hydrocortisone causes irreversible electrophysiological changes.
- To assess the impact on tympanic membrane healing.
Main Methods:
- Hydrocortisone suspension was instilled into the round window niche of rats for 5 days.
- Auditory brainstem response (ABR) thresholds were measured across multiple frequencies.
- Cochlear morphology was examined using light and electron microscopy.
- Tympanic membrane healing was monitored.
Main Results:
- Hydrocortisone significantly impaired ABR thresholds at high frequencies (12-31.5 kHz).
- These auditory deficits were irreversible, persisting for 2 months.
- No morphological damage was observed in the cochlea.
- Hydrocortisone delayed the healing of perforated tympanic membranes.
Conclusions:
- Hydrocortisone instillation can lead to irreversible high-frequency hearing loss.
- Electrophysiological changes in the inner ear occur without apparent morphological damage.
- Hydrocortisone negatively impacts tympanic membrane repair.