Three-dimensional study of the facial canal using microcomputed tomography for improved anatomical comprehension

The aims of this study were to determine the various dimensions of the normal facial canal and to identify the spatial relationships between the facial canal and its adjacent structures using microcomputed tomography (micro-CT) imaging and three-dimensional (3D) reconstruction. The petrous parts of 54 temporal bones were scanned using micro-CT with a slice thickness of 35 μm. The serial micro-CT images were used to reconstruct 3D volumes of the facial canal and the bony labyrinth with the aid of computer software. These volumes were used to measure 31 dimensions of the facial canal and its spatial relationships with adjacent structures. The length of the meatal segment, the tympanic segment, and the mastoid segment were significantly larger in males than in females (p < 0.05). The narrowest portions of the facial canal were immediately lateral to the meatal foramen in the labyrinthine segment and the midpoint of the tympanic segment. The distance between the origin of the canal for the chorda tympani nerve and midpoint of the stylomastoid foramen was 35.3% of the length of the mastoid segment, and the angle between the tympanic segment and the lateral semicircular canal was 16.3°. The angle between the mastoid segment and the canal for the chorda tympani nerve could be classified into two groups: <180° and >180°. These findings represent supplemental data for improving the detailed understanding of the facial canal anatomy.