Preventing hearing damage using topical dexamethasone during reversible cochlear ischemia: an animal model

Area of Science:

• Oto-neurology
• Pharmacology
• Surgical Innovation

Background:

• Cochlear ischemia, often caused by internal auditory artery compression during acoustic neuroma surgery, can lead to hearing loss.
• Dexamethasone delivered to the round window (RW) may permeate the cochlea to prevent ischemic injury.

Purpose of the Study:

• To investigate the protective effect of local dexamethasone application to the RW niche against cochlear damage induced by reversible ischemia.
• To evaluate the efficacy of the round window as a delivery route for dexamethasone to the inner ear.

Main Methods:

• Ten rabbits underwent internal auditory artery (IAA) compression to induce ischemia.
• Cochlear blood flow was monitored using Laser Doppler, and hearing function was assessed via transtympanic electrocochleography.
• Dexamethasone was applied to the round window niche in test ears prior to IAA compression, while control ears received saline.

Main Results:

• Laser Doppler measurements showed comparable ischemic episodes between dexamethasone-treated and control groups.
• Dexamethasone-pretreated ears exhibited 10-15% less reduction in cochlear microphonic and compound action potential amplitudes post-ischemia.
• Compound action potential latencies were shorter in dexamethasone-treated ears compared to controls, indicating preserved neural function.

Conclusions:

• The round window serves as an effective route for administering dexamethasone to the inner ear.
• Dexamethasone demonstrates a protective effect on cochlear function following localized ischemia.
• Transtympanic electrocochleography is a suitable method for monitoring auditory function during such studies.