A reliable radiologic landmark for the facial nerve in axial temporal bone computed tomography scans.

Abstract

We sought to test the reliability of a radiologic marker in identifying the vertical portion of the facial nerve in axial computed tomography (CT) temporal bone scans. At a tertiary care academic center, we used, with a random sample of 25 CT scans, a marker (the "B-line") to identify the facial nerve. The variations in distance from this marker to the facial nerve were measured. This marker, which consists of a tangent line extrapolated from the posterior border of the basal turn of the cochlea, fell within 1 mm of the facial nerve on average. The average distance from the midpoint of the posterior border of the basal turn of the cochlea to the facial nerve was 11 +/- 1 mm. This is a very reliable marker for the vertical portion of the facial nerve. This marker can be used to rapidly find the facial nerve, even in diseased or postsurgical temporal bones.