The stylomastoid area: anatomic-histologic study and surgical approach.

This three-part study explored the difficult problem of dissecting the facial nerve through the soft tissues of the mastoid tip. The anatomic relationships of the mastoid tip tissues were measured in 20 specimens. At the stylomastoid foramen, the facial nerve lies an average of 9 mm from the digastric muscle, 11 mm from the external canal, and 21 mm from the nerve's parotid bifurcation. The histologic relationships between the nerve sheath and the mastoid tip fascial tissues were examined in 10 specimens. The tight adherence of sheath and fascial fibers prevent their easy separation. By applying this new anatomic and histologic knowledge on cadaver specimens, the author refined a technique for the safe dissection of the facial nerve through mastoid tip tissues. This technique has proven successful in the operating room.