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A Comparative Study of Drug Delivery Methods Targeted to the Mouse Inner Ear: Bullostomy Versus Transtympanic Injection
Published on: March 8, 2017
Targeted therapy of the inner ear
Sangeeta Maini1, Halina Lisnichuk, Hayden Eastwood
1Department of Otolaryngology, University of Melbourne, Melbourne, Victoria, Australia.
Audiology & Neuro-Otology
|November 20, 2009
Summary
Local steroid application before cochlear implantation preserves spiral ganglion cells and hearing thresholds. This pre-treatment offers a promising strategy for hearing preservation during cochlear implant surgery.
Area of Science:
- Oto-neurology
- Surgical innovation
- Hearing restoration science
Background:
- Targeted steroid delivery to the inner ear shows potential for hearing protection during cochlear implant surgery.
- Pre-treatment of the cochlea offers optimal protection, but requires further optimization of treatment duration.
- Hearing thresholds are typically assessed for stability over a 3-month period post-hearing preservation cochlear implantation.
Purpose of the Study:
- To evaluate the efficacy of pre-operative local steroid application in preserving hearing and spiral ganglion cell (SGC) density after cochlear implantation.
- To determine the stability of auditory brainstem response (ABR) thresholds for up to 3 months following cochlear implantation in a guinea pig model.
Main Methods:
- Adult guinea pigs underwent cochlear implantation with a miniature electrode, with ABR thresholds measured pre- and post-surgery (immediately, 1 week, 1 month, 3 months).
- A polymeric sponge soaked in dexamethasone phosphate or saline (control) was applied to the round window 30 minutes before implantation.
- Spiral ganglion cell (SGC) densities were quantified from histological sections of the cochlea 3 months post-implantation.
Main Results:
- Cochlear implantation caused immediate threshold elevation, with partial recovery at higher frequencies that remained stable for 3 months.
- Dexamethasone treatment significantly reduced threshold elevation at 32 kHz immediately and sustained this effect.
- SGC densities were significantly higher in the basal turn of dexamethasone-treated animals compared to controls at 3 months post-implantation.
Conclusions:
- Auditory brainstem response thresholds remain stable for 3 months after cochlear implantation in guinea pigs.
- Local steroid application to the inner ear prior to cochlear implantation effectively preserves spiral ganglion cell populations.
- This pre-treatment strategy is effective in maintaining residual hearing at the time of implantation.
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