engleski

An animal model of cochlear implantation with perlymphatic drug delivery

Drug delivery to the inner ear is an interesting mean of achieving high local doses while avoiding general side effects. It is also a promising approach to maintain residual hearing during and after the cochlear implantation. Otoprotective components could be released through microcatether located inside the electrode carries. The conception of an animal model is a first step to assess different molecules before human clinical trials. Guinea pigs with normal hearing were implanted with a prototype electrode carrier (MED-EL0 that comprised the electrode and a microcatheter that was connected to an osmotic minipump (Alzet). The tested drug was the antioxidant n-acetyl-cysteine: artificial perylimph was injected as a control. Hearing threshold were evaluated with auditory brainstem responses (click tone bursts) before, immediately after the implantation, and at day 7 and day 30 postoperatively. Histological study of the cochlea was performed at day 30. Some animals had a CT-scan to check the implant position at day 30. An immediate postoperative hearing loss of 35 dB (click simulation) was observed. It remained stable at day 7 and at day 30. Preliminary analysis did not find any protective effect on hearing preservation from N-acetyl-cysteine. The average loss in the control group was 33dB. CT scan images showed that implants were introduced in the basal turn of the cochlea at the depth varying from 270 to 360 degrees, and that implants stayed in good position during one month. This animal model is simple and reproducible. It mimics the cochlear trauma generated during cochlear implantation and would allow the evaluation of drugs to achieve a better preservation of residual hearing (e.g. antioxidants, corticoids or growth factors).

Antioxidants; hearing preservation; cochlear implant

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