Measurements of the facial recess anatomy: implications for sparing the facial nerve and chorda tympani during posterior tympanotomy.

Posterior tympanotomy is commonly performed through the facial recess to facilitate cochlear implantation. A rare but serious complication of this procedure is paralysis of the facial nerve and/or the chorda tympani. These complications generally occur because of a limited understanding of the anatomy of the facial recess. To help further define this area, we used computer-aided design software to measure (1) the angle between the facial nerve and the chorda tympani nerve and (2) the distance between the takeoff point of the chorda tympani and the posteriormost prominent point of the short process of the incus in 30 cadaveric adult temporal bones. The mean angle was 23.58° (±6.84), and the mean distance was 7.78 mm (±2.68). Our most important finding was that there was a correlation between the two measurements in that the distance tended to be greater when the angle was less than the mean and vice versa. This trend approached but did not quite reach statistical significance (r = -0.248, p = 0.059).