R435 – Stapedius Muscle Relations to the Facial Canal

Abstract

Problem The gross anatomical variations of the stapedius muscle and its relations to the facial nerve canal. Methods Thirty-five temporal bones were dissected, and the anatomic details were studied utilizing an operating microscope and otoendoscopes with 0o, 30o and 70o angles and 2.7 and 3 mm diameters. The muscle origin, its course in its bony sulcus with its relation to the facial nerve canal, the tendon and its insertion were studied. Results Marked variations in the origin, size, and course of the muscle in its bony sulcus were detected. The shape of the sulcus itself and its relation to the facial nerve canal varied also, both mainly influenced by the sinus tympani development. These variations affected the shape and length of the tendon and the pyramidal eminence. In addition, they influenced the site of tendon insertion into the stapes. The presence of ectopic muscle bundles was confirmed in one specimen. Conclusion The stapedius muscle anatomy can vary significantly from one temporal bone to another. In some situations these variations can be of surgical importance worse enough to be recognized. Significance To add important unrecognized data to the surgical anatomy of the temporal bone.