Evaluation of the effect of ototopical neomycin on spiral ganglion cell density in the guinea pig.

The development of a reproducible unilateral deafness animal model was the primary objective of this study. Because of its importance in the function of cochlear prostheses, the status of the VIIIth nerve was used as the measure of deafness. The effect of a concentrated neomycin solution applied locally to the middle ear of the guinea pig was evaluated. Spiral ganglion cell survival was quantitated at 1, 2, 4, 6 and 10 weeks after exposure. Although the intermediate time periods showed moderate inter-animal variability, by ten weeks, consistent spiral ganglion cell loss was seen with maximum cell loss at the extreme apex (18.8% of control) and base (30.3% of control) and maximum cell survival in the lower middle turns of the cochlear spiral (53% of control).