Analysis of spiral ganglion cell populations in children with normal and pathological ears.

Abstract

This study analyzed features of total and segmental spiral ganglion cell populations in children with normal ears and those with various pathological conditions. Sixty-three human temporal bone specimens, obtained from 43 children 4 days to 9 years of age, were studied histopathologically. These specimens were divided into 5 diagnostic groups: group 1, normal ears (13 ears); group 2, congenital infectious diseases (13 ears); group 3, chromosomal aberrations (11 ears); group 4, multiple craniofacial anomalies with hereditary or genetic causes (21 ears); and group 5, perinatal and postnatal asphyxia (5 ears). Eighteen of the 63 ears had documented profound deafness. In either normal ears (group 1) or those with various pathological conditions (groups 2 through 5), the total number of ganglion cells did not change as a function of age during the first 10 years. The total number of ganglion cells was significantly larger in group 1 (33,702) than in each of groups 2, 3, 4, and 5 (p < .01), and the number was significantly larger in group 2 than in each of groups 4 and 5 (p < .01 and p < .05, respectively). The ratio of basal to apical ganglion cell populations remained constant in both normal and pathological ears. Each ratio of the number of basal and apical ganglion cells in groups 2, 3, 4, and 5 to the mean number in group 1 (basal and apical survival ratios) was at least approximately 40%. There was no statistical difference between these two ratios in groups 2, 3, 4, and 5. The mean (+/-SD) total number of ganglion cells in ears with documented profound deafness was 15,417 +/- 5,944, which is approximately 40% of those present in normal ears. Our results suggest that normally, cochlear neurons are completely present at birth and minimally regress during the first decade of life. In addition, although intergroup differences among various pathological groups were present, the majority of pathological ears had more than 10,000 spiral ganglion cells present. Cochlear implantation has gradually been recognized as an effective and reliable tool for rehabilitation of children who have profound deafness, even congenitally or prelingually deafened children. On the basis of the results obtained in this study, we discuss the implications for cochlear implantation in children.