It has previously been shown that following loss of the organ of Corti in guinea pigs, over 80% of the spiral ganglion cells degenerate. Humans who lose their hearing from aminoglycoside toxicity, meningitis, and other sensory deafness probably also undergo auditory neural degeneration which may limit the potential benefit from cochlear implants which are usually implanted months-to-years later. Animal studies have shown that more spiral ganglion cells survive if the cochlea is electrically stimulated. We have pilot data demonstrating that exogenous GM1 ganglioside treatment also increases spiral ganglion cell survival following organ of Corti loss. The proposed experiments will determine the effects of electrical stimulation, gangliosides, and their interactions on maintaining structural and functional integrity of the auditory system following organ of Corti loss. They will also demonstrate if the ganglioside treatment has a dosage effect, if electrical stimulation has a stimulus level effect, if extra- cochlear stimulation is as effective as intracochlear stimulation, and the effect of bipolar vs. monopolar stimulation at different depths in the scala tympani. These findings will be clinically relevant in determining a potential non-invasive or minimally invasive means of sustaining the neural population in the recently deafened patient until he/she can receive an appropriate cochlear implant (or other future device).
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