The labyrinthine portion of the facial canal. A comparative radioanatomic investigation.

The variational radiographic anatomy of the labyrinthine portion of the facial canal was investigated in 200 plastic and silicone casts of unselected temporal bone specimens by means of multidirectional and computed tomography in different projections. The labyrinthine portion of the canal varied considerably in shape and size; in some specimens the cross-section was circular, but often the canal was crumpled and flattened in its passage above the cochlea. The medial part of the labyrinthine portion was narrowest, the lowest cross-sectional area being 0.5 mm2. In spite of optimal positioning of the specimen it was not always possible to reproduce the entire labyrinthine portion of the canal completely. Most difficult to reproduce were specimens with extremely small vertical diameters and marked caudal sloping of the canal.