The spiral ganglion and hair cells of Bronx waltzer mice.

Inner hair cells and spiral ganglion cells were counted in a mutant mouse strain (Bronx waltzer) reported to have very few of these cells (6) in order to determine if the remaining ganglion cells would be predominantly type II cells. These cell counts indicate a 50% reduction of spiral ganglion cells in Bronx waltzer cochleas compared to normal mice. Averaged throughout the cochlea about 11% of the remaining cells are type II cells while in normal mice this percentage is 5%. In some regions however, as many as 20% of the remaining cells are type II cells. Counts of IHC in surface preparations reveal 37 normal looking IHC (about 5% of the normal population) in each of two Bronx waltzer mouse cochleas. There were also about 120 shrunken IHC in each cochlea, representing 17% of the normal cell population. While there appears to be an increased proportion of type II cells in the Bronx waltzer spiral ganglion there are also many more type I cells than might be expected from the small number of IHC.