The Depth of Facial Nerve in the Mastoid Bone

Background The hallmark of the temporal bone is variation. Various important structures like the facial nerve run in the temporal bone at various depths can be injured during mastiodectomy.

Method Twenty wet cadaveric temporal bone were dissected. A cortical mastoidectomy was performed followed by a canal wall down mastiodectomy and the depth of the vertical segment of the facial nerve in the mastoid was determined.

Results The mean depth of the second genu was 13.8 mm. The mean depth of the stylomastiod foramen was 12.75 mm and the mean distance from the annulus at 6’0 clock to the stylomastoid foramen was 10.22 mm.

Conclusion There is significant variation in the average depth of the facial nerve in the mastoid.