Postnatal Development of the Internal Auditory Canal Studied by Computer-Aided Three-Dimensional Reconstruction and Measurement

Abstract

Postnatal development of the internal auditory canal (IAC) was investigated in 20 normal human temporal bones obtained from individuals 1 month to 72 years old. Computer-aided three-dimensional reconstruction and 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 lengthening of the part of the IAC medial to the foramen singulare. The lengths 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. Postnatal increases in the volume of the IAC followed patterns similar to that of increases in length of studying the shape of the IAC. Postnatal increases in the volume of the IAC followed patterns similar to that of increases in length of the IAC walls. These results show that postnatally the IAC increases significantly in length until about 10 years of age and slightly in diameter until about 1 year of age, especially medial to the foramen singulare. This concentration of growth of the IAC medially implies that its postnatal development is mainly due to growth of the bone around the otic capsule, which has implications for IAC surgery.

The bony cochlear nerve canal in children with absent or hypoplastic cochlear nerves

“…The BCNC and IAM width was measured to the nearest 0.1 mm. A small IAM was defined as a width of less than 3 mm [17][18][19][20]. Statistical analysis was done using SPSS [Statistical Package for Social Sciences].…”

Auditory Neuropathy Characteristics in Children with Cochlear Nerve Deficiency

“…One of these two ears with normal cochlear nerves and absent DPOAEs had a sensorineural hearing loss; behavioral audiometric testing results are currently unavailable for the other ear (i.e., patient). In all, only (Olivares & Schuknecht, 1979;Sakashita & Sando, 1995 …”

“…The terms aplasia, hypoplasia, agenesis, or degeneration are avoided so as to not imply a mechanism or causality, because this remains speculative. A small IAC is defined as Յ3 mm on cross-sectional diameter (Olivares & Schuknecht, 1979;Sakashita & Sando, 1995). The various inner ear malformations have been described previously (Buchman, Copeland, Yu, et al, 2004).…”

Temporal bone and cranial nerve findings in pontine tegmental cap dysplasia

“…A partitioned IAC, as defined in that study, was not considered duplicated. IAC stenosis was defined as width <3 mm in greatest cross-sectional dimension at the mid-canal level [19][20][21]. VCN canal stenosis was similarly defined in cases of IAC duplication.…”