Systemic immunity influences hearing preservation in cochlear implantation.

Abstract

HYPOTHESIS:

To determine whether a systemic immune response influences hearing thresholds and tissue response after cochlear implantation of hearing guinea pigs.

METHODS:

Guinea pigs were inoculated with sterile antigen (Keyhole limpet hemocyanin) 3 weeks before cochlear implantation. Pure-tone auditory brainstem response thresholds were performed before implantation and 1 and 4 weeks later. Dexamethasone phosphate 20% was adsorbed onto a hyaluronic acid carboxymethylcellulose sponge and was applied to the round window for 30 minutes before electrode insertion. Normal saline was used for controls. Cochlear histology was performed at 4 weeks after implantation to assess the tissue response to implantation. To control for the effect of keyhole limpet hemocyanin priming, a group of unprimed animals underwent cochlear implantation with a saline-soaked pledget applied to the round window.

RESULTS:

Keyhole limpet hemocyanin priming had no significant detrimental effect on thresholds without implantation. Thresholds were elevated after implantation across all frequencies tested (2-32 kHz) in primed animals but only at higher frequencies (4-32 kHz) in unprimed controls. In primed animals, dexamethasone treatment significantly reduced threshold shifts at 2 and 8 kHz. Keyhole limpet hemocyanin led to the more frequent observation of lymphocytes in the tissue response to the implant.

CONCLUSION:

Systemic immune activation at the time of cochlear implantation broadened the range of frequencies experiencing elevated thresholds after implantation. Local dexamethasone provides partial protection against this hearing loss, but the degree and extent of protection are less compared to previous studies with unprimed animals.

• Authors: Melanie Souter, Hayden Eastwood, Paul Marovic, Gordana Kel, Sarin Wongprasartsuk, Allen F Ryan, Stephen John O'Leary
• Journal: Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology (Otol Neurotol) Vol. 33 Issue 4 Pg. 532-8 (Jun 2012) ISSN: 1537-4505 [Electronic] United States
• PMID: 22470051 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• Adjuvants, Immunologic
• Anti-Inflammatory Agents
• Dexamethasone
• Hemocyanins
• keyhole-limpet hemocyanin

Topics

• Adjuvants, Immunologic (pharmacology)
• Animals
• Anti-Inflammatory Agents (pharmacology)
• Audiometry, Pure-Tone
• Auditory Threshold (drug effects)
• Cochlear Implantation (adverse effects)
• Cochlear Implants (adverse effects)
• Dexamethasone (pharmacology)
• Disease Models, Animal
• Drug Administration Routes
• Guinea Pigs
• Hearing Loss (drug therapy, immunology)
• Hemocyanins (immunology, pharmacology)
• Round Window, Ear (drug effects)