ANATOMY OF THE AUDITORY TUBE - CT AND MR IMAGING APPEARANCE

The auditory tube is a bony and cartilaginous canal which connects the middle ear to the nasopharynx. The bony portion (protympanum), explored by computed tomography, is cone shaped, with a posterior base. The main relations are : the intrapetrous carotid, the tensor tympani muscle, the middle cerebral fossa and temporo-mandibular joint. The fibrocartilaginous portion is explored by computed tomography and mainly by magnetic resonance. The fibrocartilaginous tube is posteromedial; its upper margin is curled outward to form the roof of the cartilaginous tube. Anterioly and Laterally, the auditory tube is closed by a fibrous membrane extending along the inferior surface of the auditory tube to form its floor. The auditory tube is in contact with two main muscle : the tensor veli palatini anterolateral and the levator veli palatini posterolateral and inferior. They are bounded by fascia : the intrapharyngeal fascia is medial, the pharyngo basilar fascia (salpingopharyngeal fascia of Trolstch, is between the tensor and levator veli palatini muscles ; the fascia of Wever Liel is lateral to the tensor veli palatini. The auditory tube and its muscles form the lateral wall of the rhinopharynx and prevent the extension of a pathologic process to the para pharyngeal and infratemporal spaces.