A comparative study of the fallopian canal at the meatal foramen and labyrinthine segment in young children and adults.

If entrapment is a critical factor in pathogenesis, the lower incidence of Bell's palsy in children compared with adults may have an anatomical basis. Histologic sections of 20 temporal bones from children younger than 2 years were examined to determine the diameter of the facial nerve and fallopian canal at the meatal foramen and in the labyrinthine segment. No statistically significant difference in the nerve/canal ratios in these areas was found. Comparisons were made with similar data from 10 adult temporal bones. The nerve/canal ratios in the labyrinthine portion were similar in both age groups; however, the ratio at the meatal foramen was significantly smaller in children. This may be due, in part, to growth of the vertical crest, which was found to increase considerably in length and width by adulthood. These results suggest that the facial nerve is not as tightly contained at the meatal foramen in children and provides a possible explanation for the relative infrequency of Bell's palsy in this age group.