Clinical Anatomy of the Eustachian Tube
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Clinical Anatomy of the Eustachian Tube
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Eustachian tube assessment methods Cartilage Lumen: Rüdinger’s safety canal, auxiliary gap and microturbinates Muscles Ligaments Medial and lateral Ostmann’s fat pad
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Introduction
Although there were very early postulations of an airway between the middle ear and the upper airway by Aristotle [40], Bartolomeo Eustachio was the first to exactly describe the auditory tube [146]. It was Valsalva who posthumously suggested naming the auditory tube after its discoverer [7]. Eustachio believed that the tube had to be open under normal conditions [155]. Also, the anatomist Duverney claimed the Eustachian tube (ET) to be permanently open, but he described the airway as bidirectional and claimed there was a second function of the tube: the clearance of fluids from the middle ear [40]. The Eustachian tube anatomy and its clinical significance have been studied using human cadaveric temporal bone specimens as well as CT and MRI studies of living subjects [191]. However, some details should still be discussed. The Eustachian tube is divided into an osseous posterolateral and a fibrocartilaginous anteromedial portion. Whereas the osseous portion is mainly formed by the petrous part of the temporal bone, the anatomy of the flexible fibrocartilaginous portion is more complex. It is quite obvious that the fibrocartilaginous portion represents the active Eustachian tube function, but the understanding of how the surrounding elements interact remains controversial. For example, there is a contradictory discussion about the 3D anatomy and function of the tensor veli palatini muscle [52]. Luschka [101], Rüdinger [161]
J.L. Dornhoffer et al., A Practical Guide to the Eustachian Tube, DOI 10.1007/978-3-540-78638-2_1, © Springer-Verlag Berlin Heidelberg 2014
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Clinical Anatomy of the Eustachian Tube
and Proctor [147] called the tensor veli palatini muscle a “dilatator tubae”. Dayan et al. [26] also used this term, but they noticed that the two portions of the tensor veli palatini muscle have different mechanical purposes and thus justified the use of the word “tensor”. Seif and Dellon [175], on the other hand, called the tensor veli palatini muscle a “compressor tubae”. Finally, Pahnke [135] and Gannon et al. [47] described both its impact upon the opening as well as closing function of the Eustachian tube. It is one of the key merits of Joseph Toynbee to point out that the Eustachian tube is closed at rest and that it only opens for a short period when swallowing [190]. In fact, the Eustachian tube, its numerous morphologic variations [132] and its developmental changes [36] as well as its opening and closing function [70] are still difficult to understand today. MRI is an excellent method to assess the anatomical landmarks in and around the Eustachian tube [99]. Even the opening and closing function can be demonstrated when using appropriate protocols [93]. However, not only MRI, but also low-dose sequential CT scans are suitable to assess the anatomy as well as the
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