The Nasopharyngeal Orifice of the Auditory Tube: Implications for Tubal Dynamics Anatomy STEWART R. ROOD, Ph.D. WILLIAM J. DOYLE, Ph.D. Pittsburgh, Pennsylvania 15213 This is the first part of a study designed to clarify the relationship between auditory tube dilation and observed movement of the naso- pharyngeal orifice of the tube. This report seeks to delineate the anatomical parameters of the system, whereas, the second will report on findings of torus 'movement' observed during simultaneous tympan- ometric measurement of tubal function during swallowing. The dispo- sition of the paratubal musculature, relation between the tubal cartilage and the cranial base, relations between the cartilage and the medial pyterygoid plate, relation between the two cartilaginous laminae, and the presence of a heavy coat of soft tissue over the torus were findings felt to indicate that movement of the tubal cartilage in swallowing cannot occur. Nasopharyngoscopic reports of "cartilage" movement during swallowing may be observations of soft tissue sliding over the torus and not torus movement itself. KEY WORDS: Eustachian tube, Torus tubarius, Nasoendoscopy, Anatomy The mechanism by which the auditory tube the results of studies involving animal models. is dilated is still a matter of some debate. The latter are perhaps the most enlightening Various muscles and muscle systems have in view of this more direct approach to settling been suggested as being responsible for the this issue. observed tubal opening during deglutition. The various studies reported show clearly These mechanisms have been based on ana- that the tensor veli palatini muscle is the sole tomic and physiologic evidence as well as on and sufficient functional dilator of the Eus- tachian tube in dogs (Rich, 1920) and in the Dr. Rood is Assistant Professor, Department of Oto- Rhesus monkey (Macaca mulatta; Cantekin laryngology, University of Pittsburgh School of Medicine, Eye and Ear Hospital, Pittsburgh Pennsylvania. Dr. et al., 1979), the two animals studied most Doyle is Assistant Professor, Department of Otolaryngol- intensively. Extrapolation of the mechanisms ogy, University of Pittsburgh School of Medicine, Chil- observed in these animal models to man has dren's Hospital, Pittsburgh, Pennsylvania. Correspond- been criticized. This has occurred in spite of ence should be addressed to Stewart R. Rood, Ph.D., the reported marked similarity in the anat- 1115 Eye and Ear Hospital, 230 Lothrop Street, Pitts- burgh, PA 15213. , . omy and function of the auditory tube and Presented in part at the Mid-winter Meeting, Associ- middle ear between the Rhesus monkey and ation for Research in Otolaryngology, St. Petersburg, man (Doyle and Rood, 1979). Direct studies Florida, January 21-23, 1980. of this system in man are not feasible, and, This study was supported in part under Grant #1PO NS16337 from NINCDS of the National Institutes of consequently, we must rely upon such evi- Health, to the Department of Otolaryngology, Children's dence as the observed dilations at the naso- Hospital of Pittsburgh. pharyngeal orifice which accompany swallow- 119 120 Cleft Palate Journal, April 1982, Vol. 19 No. 2 ing. It is, therefore, the purpose of this study Dellon, 1978). It has been presented with to outline the anatomy of the auditory tube some modifications for over a century. This is and its associated musculature and to relate supported by the observed movements of the this to possible imposed constraints and limi- tissue surrounding the nasopharyngeal orifice. tations on tubal mechanics. One of the first authors to present his ob- servation illustrating the role of the levator Review of the Literature veli palatini muscle in tubal functions was Two basic mechanisms of auditory tube Cleland, who, in 1869 observed that the lower dilation have been proposed for man. The margin of the auditory tube was "spas- first is supported by anatomical and func- modically twitched up" during swallowing. tional studies in man and more direct evi- Simpson and Witcher (1947) and Simkins dence from animal models. This model (1943) also describe various mass tubal move- (Honjo et al., 1979) assumes that the auditory ments which involved the torus tubarius ro- tube is basically fixed to the cranial base and tating counterclockwise about an axis passing that functional dilation is accomplished by through the tubal lumen. The mechanistic contraction of the medial bundle of the tensor explanation for these movements was first veli palatini muscle (Rood and Doyle, 1978). postulated by Bryant (1907). He reported that The second model involves both the tensor the medial cartilaginous lamina is hinged su- and the levator veli palatini muscles (Seif and periorly and swings freely at its line of attach- FIGURE 1. A photomicrograph obtained from a 1.5 mo. old otologically normal specimen (at the junction between the anterior third and middle third of the cartilaginous tube) illustrating the relationship between the tubal cartilage (A), the levator veli platini (C) and tensor veli palatini (D) muscles. An "accessory" piece of cartilage is also shown (B). The cartilage, shown here in its crooked shaped configuration, is a continuous piece of cartilage, with lateral (2) and medial (1) aspects. The description of lateral and medial laminae which are joined at the dome of the cartilage is not supported. (Original magnification-15%) Rood & Doyle, oriricE 121 ment. The primary force responsible for tubal levator veli palatini muscle and various types dilation is purportedly the posteromedial of tubal rotation have been suggested (Schu- pressure of the levator veli palatini muscle on knecht, 1974). the angular process of the medial cartilage Common to the majority of these reports is which then swings "backward, upward, and an anatomic description of the tensor veli inward, dragging with it the floor of the tube palatini (TVP) as being single bundled and and thereby forming a triangular orifice" lacking a direct tubal attachment. However, (Bryant, p.934). Bryant did not report a role past and more recent anatomic studies have for the tensor veli palatini muscle in tubal demonstrated conclusively that the TVP mus- dilation. A similar mechanism of tubal dila- cle is a composite muscle consisting of a lateral tion was postulated by Simkins (1943), though bundle (TVP proper) with bone to bone at- he ascribed to the tensor veli palatini muscle tachments (in agreement with Seif and Del- the role of tubal closure. More recently, Seif lon) and a medial bundle (the dilatator tubae and Dellon (1978) reiterated these positions muscle) which takes its origin directly from and suggested a more active function for the the posterior 1/3 of the lateral membranous tensor veli palatini muscle. They reported wall of the auditory tube and is attached on that this muscle is only capable of isometric its other end to the deep surface of the TVP. contraction. By increasing its bulk along the The vector of this muscle has been described lateral tubal margin, it may serve to passively (Doyle, 1977) for adults of various popula- assist the motion of the levator veli palatini. tions and is potentially effective in dilating More complicated hypotheses involving the the auditory tube by inferolateral displace- FIGURE 2A. The tensor veli palatini (lateral bundle) viewed from the lateral aspect. 1-the lateral bundle of tensor veli palatini; 2-the lateral lamina of the auditory tube cartilage; 3-the lateral membranous wall of the auditory tube retracted somewhat; 4-the cranial base. 122 Cleft Palate Journal, April 1982, Vol. 19 No. 2 FIGURE 2B. The medial bundle (2) of the tensor veli palatini muscle (dilatator tubae) or seen with the lateral bundle removed. 1-the muscle as it rounds the hamulus; 2-the dilator tubae muscle; 3-the lateral cartilaginous lamina; 4-the cranial base; 5-the lateral membranous tubal wall. ment of the lateral tubal wall. Consequently, graphic and narrative documentation the more complicated mechanisms of tubal was maintained of all pertinent observa- dilation which implicitly deny this insertion tions, e.g. cartilage-cranial base relation- are at best of secondary functional impor- ship, cartilage-pyterygoid plate relation- tance. This report addresses the anatomic po- ship, and disposition of the paratubal tential for the more complex movements as- musculature. sumed under the model of tubal dilation by One side from each of six human ca- contraction of the levator veli palatini muscle. daver heads (in addition to the above) was dissected as above but studied with Materials and Methods specific attention to the soft tissue sheath Several research protocols were developed overlying the torus tubarius. Measure- in order to obtain anatomic data deemed ments were taken of the thickness of the relevant to the basic question of the reality of tubal cartilage at the lateral lanima, with tubal cartilage movement, of whatever sort, and without its soft tissue sheath. during swallowing. Five anteroinferiorly extended temporal 1. One side from each of seven adult hu- bone specimens, excised at autopsy in man cadaver heads was dissected using accordance with the procedure outlined standard dissection instruments. When by Rood and Doyle (1981), were pro- necessary, dissection was carried out us- cessed for light microscopy. The speci- ing a Zeiss binocular operating micro- mens (ages: 1.5 mo., 3 mo., 13 yrs., 21 scopic for magnification. No quantative yrs., and 27 yrs.) were decalcified in tri- measurements were obtained. Photo- chloroacetic acid, embedded in celloidin, Rood & Doyle, nasorHarynorar ortrice 123 sectioned at 25-30 um, and stained in 5) Relation of the soft tissue sheath to the hematoxylin and eosin. Tubal cross-sec- anterior termination of the tubal carti- tions and longitudinal sections were stud- lage. ied. Wide field, lowpower photomicro- graphs were obtained using a Micro- 1. ParatuBatr MuscutatTuURE Nikor 55 mm lens coupled to a Bowens Figure 1 shows the disposition of the two Illumatron. primary muscles associated with the auditory tube.