[Bone mineral density of the internal auditory meatus by quantitative computed tomography]

The bone mineral density of the internal auditory meatus was investigated by means of quantitative computed tomography in 20 normal subjects (40 ears). Investigated portions of the internal auditory meatus were the porus anterior and posterior and the fundus anterior and posterior. Two other portions of the ear, the bony vestibule and lateral wall of the mastoid, were also investigated. The bone density values (calcium carbonate equivalent value) for each portion were analyzed statistically. The following results were obtained: 1) There was no significant difference between the right and left values in any portion. 2) The highest mean value was found in the fundus posterior, the lowest in the porus anterior. There was a significant difference between the values of the fundus and porus. Bone hardness generally correlates with bone density. Thus, the bone hardness of the porus of the internal auditory meatus was appraised to be lower than that of the fundus. These results suggest that this is one of the factors promoting enlargement of the internal auditory meatus in acoustic neuroma.