POSTNATAL-DEVELOPMENT OF THE INTERNAL AUDITORY-CANAL STUDIED BY COMPUTER-AIDED 3-DIMENSIONAL RECONSTRUCTION AND MEASUREMENT

Postnatal development of the internal auditory canal (IAC) was investi gated in 20 normal human temporal bones obtained from individuals 1 mo nth to 72 years old. Computer-aided three-dimensional reconstruction a nd measurement of bones showed that the superior, inferior, anterior, and posterior walls of the IAC lengthen significantly from birth until about 10 years of age, with development mainly attributable to length ening of the part of the IAC medial to the foramen singulare. The leng ths of the part of the IAC lateral to the foramen singulare and of the transverse crest and Bill's bar did not appear to develop postnatally . The IAC diameter increased slightly at the porus for about the first year after birth, but not at the fundus or the middle portion of the canal. This finding was confirmed by studying the shape of the IAC. Po stnatal increases in the volume of the IAC followed patterns similar t o that of increases in length of the IAC walls. These results show tha t postnatally the IAC increases significantly in length until about 10 years of age and slightly in diameter until about 1 year of age, espe cially medial to the foramen singulare. This concentration of growth o f the IAC medially implies that its postnatal development is mainly du e to growth of the bone around the otic capsule, which has implication s for IAC surgery.