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Home , Larynx, Thyroid cartilage

1 ORIGINAL ARTICLE ULTRASONOGRAPHY: An alternative technique in the evaluation of the aero-digestive crossroad.

Dr. Agustin Arruti (1), Dra. Marie Poumayrac (1)

Abstract-

The larynx is a high complexity , crossroad of the airway and digestive tract which has a small size and mobility in different planes; all this makes the study very difficult. Computed tomography (CT) and magnetic resonance (MR) are used for larynx evaluation, both have limitations. Ultrasonography (US) is an innocuous accessible and non expensive study, which can be performed in the patient bed. Because its high spatial resolution it constitutes nowadays the study of election in most of soft tissue pathology. In addition, US, allows evaluation in real time of the different structures, which is relevant on those that present movement. The aim of this study was to determine the role of US in the evaluation of the larynx and structures functional and anatomically related to it. 40 patients, (randomly selected from the population of the Pasteur hospital) were studied with high resolution US, using a high frequency linear probe (up to 10 MHz) attached to Simmens Acusson equipment. Previously an objective system for evaluation of those larynx components that in authors opinion had more relevance was designed. These components were selected because of their anatomic, physiologic and pathologic importance (i.e. , cricoid, aritenoid ; , pre-epiglotic space, true and false , etc). US evaluation of those components of the larynx is possible. US is a relatively innocuous method that has the best spatial resolution, which can be useful in the study of different larynx pathologies. This is why we suggest US as an alternative and complementary technique.

Kee words- Larynx ultrasonography, neck ultrasonography, high resolution ultrasonography.

1-Pasteur Hospital residents Contact- [email protected] Rev Imagenol, 2010, 14(1):30-36.

LARYNX ULTRASONOGRAPHY: an alternative technique in the evaluation of the aerodigestive crossroad

I) OBJECTIVES- was designed. These components were selected because of their anatomic, General- physiologic and pathologic importance. To determine the use of US in the evaluation of the larynx as well as the III) RESULTS- structures anatomical and functionally related to it. A) The sample selected was composed by Specific- 50% males and 50% females. There were Determine the rol of US in: 37,5% between 21 and 49 years, 27,5% I) Visualization of: thyroid, crocoid, between 50 and 69 years, 25% above 70 aritenoid cartilages, as well as years and only 10% below 20 years of age. ultrasonographyc characteristics of The percentages of structures visualized by each one of these cartilages. the authors are shown in table 1 and II) Visualization of vocal cords and graphic 1. ventricular bands, as well as their US characteristics. III) Evaluation of hiotiroepiglothyc space and its US characteristics. IV) Evaluation of some of the intrinsic and extrinsic larynx muscles and their characteristics.

II) MATERIAL AND METHODS-

We studied 40 patients randomly selected from the population of the Pasteur Hospital with high resolution US using a high frequency linear probe (up to 10 MHz) attached to Simmens Acusson equipment. We used a high resolution setup (testicle), a 10 Mhz frequency, two superficial focuses and we adapted this settings to the findings. Patients were studied laid down in supine position, with their neck hiperextended (achieved with a pillow under their shoulders). They were asked to breathe Thyroid and cricoid cartilages were normally. visualized in 100% of patients, whereas We initiated the study of the larynx in the arytenoids were seen in only 75% of cases. axial plane identifying the thyroid , In 100% of the population we were able to which we used as a landmark for the rest of identify the hiotiroepiglotic and inter- crico- the study. Then we used coronal, sagital thyroid spaces. The anterior commissure and oblique planes. After this we asked the was identified in 67,5% and the peri-cricoid patient to perform Valsalva manoeuvers space in a 65%. and of a long “a” with the Another objective was to define the intention of evaluating the vocal cord percentage of visualization of the vocal motion and vibration. cords and the ventricular bands, which Previously an objective system for the were visualized in 72,5% of the patients. evaluation of those larynx components that The thyro-hyoid and crico-thyroid in the authors‟ opinion had more relevance membranes were visualised in all patients.

3 ORIGINAL ARTICLE The crico-thyroid and thyro-hioid muscles B) ANATOMIC BACKGROUND- were seen in 100% of the cases whereas the thyro-aritenoid muscle was seen in The larynx is part of the airway and the 80%. phonation organ. We always identified the hyoid bone. It is composed by multiple mobile cartilages; articulations and bond to each other and to the structures that surround them. It‟s also composed by muscles and a mucosa.

CARTILAGES- There are normally eleven cartilages, three odd middline cartilages: thyroid, cricoid and epiglottic and four paired lateral cartilages: aritenoid, Santorini‟s, Morgagni‟s and sesamoids. We will describe only the thyroid, cricoids, aritenoid and epiglotic cartilages.

The is located in the inferior portion of the larynx; it has a ring shape, composed by an anterior segment The presence of calcifications in the thyroid named the cricoid arch and a posterior and cricoid cartilages was responsible for segment or the cricoid plaque. (Fig. 1) not identifying the aritenoid cartilages, the vocal cords, ventricular bands, the thyro- The is situated above the aritenoid muscle and the movements and cricoid arch. It is composed by two vibration of the cords. In table and graphic 2 quadrilateral plates binded at the anterior and 3 we represent these findings. edge, forming a dihedral angle that points backwards. Its posterior edge continues up and downwards with the mayor and minor apophysis respectively. (Fig .1)

The epiglottic cartilage is located in the antero-superior portion of the larynx, behind the thyroid cartilage, which exceeds. It forms the skeletal frame of the . (Fig. 1)

The aritenoid cartilages are two small cartilage pieces with pyramid shape, located above the lateral portion of the cricoid ring. Two of the angles of the base of this pyramids, give origin to the vocal and muscular apophysis. The first one gives insertion to the posterior and lateral crico- aritenoid muscles and the second one gives insertion to the vocal . (Fig. 1)

Rev Imagenol, 2010, 14(1):30-36.

LARYNX ULTRASONOGRAPHY: an alternative technique in the evaluation of the aerodigestive crossroad

ARTICULATIONS AND LIGAMENTS- postero-superior edge of the body and the interior edge of the mayor apophysis of the We will analyze only the ligaments that are hioid bone. (Fig. 1 and 5) relevant to this article. MUSCLES-

The crico-thyroid membrane also known as There are two types of muscles in the the middle crico-thyroid ligament, extends larynx, extrinsic and intrinsic. The first from the middle part of the inferior edge of group has an insertion in the larynx and in the thyroid cartilage to the superior edge of the structures that surround it. The second the cricoid arch. (FIG1). group has both insertions in the larynx. (Fig. 3)

The larynx mucosa is reinforced in all its INTERNAL CONFIGURATION- extension by an elastic membrane that has two thickenings called the superior and The inner surface of the larynx presents on inferior thyro-aritenoid ligaments. The each side in its middle portion, two superior ligaments are continued by the superposed folds, which are oriented in the ariteno-epiglottic ligaments. All of these antero-posterior axis. They are called the structures form the fibrous frame of the vocal cords and the ventricular bands (FIG. larynx vestibule. The inferior ligaments 4 y 5). Between them we found the constitute the elastic cone of the larynx Morgagni ventricles, two diverticula of the whose free edge forms the vocal ligament. larynx lumen. The vocal cords divide the (Fig1) larynx lumen in three levels; superior or supra-glotic also known as the larynx The thyro-hioid membrane extends from the vestibule, middle or glotic level, and inferior superior edge of the thyroid cartilage to the or sub-glotic level. (Fig. 1 and 4)

5 ORIGINAL ARTICLE FUNCTIONALITY- the inferior apophysis. The maximum thickness of the plates was, in our The larynx is the entrance into the inferior population; 4,7mm average on the right airway and the organ of phonation. side and 4,6mm average on the left. When the larynx lumen closes as it opens into the protecting the The cricoid cartilage was homogeneously airway. This mechanism is accomplished by hiperechoic related to the thyroid cartilage. the epiglottis that occludes the upper When there were no complications it could opening of the larynx assisted by the be correctly studied by us. ventricular bands, which ensures a In an axial plane, the circular configuration complementary occlusion and the airway of the ring of the cartilage was protection. That is why the superior level characteristic. Many times the cricoid functions as the protection apparatus of the plaque remained hidden or was confused airway. with the aritenoid carilages and the muscles The larynx cartilages, the vocal cords, the and its insertions between them. The elastic cone, their articulations and thickness of the anterior portion of the ring muscles, constitute the sound producing was, in our population, 2,5mm, whereas its apparatus. This sound is modified by the lateral portion measured 4,8mm and 4,9mm resonance in the superior levels, at the average on the right and left sides larynx, pharynx, and nose, were the respectively. The calcifications in this voice takes character. cartilage also were, partial or total, they were present in 52, 5% of the cases; being C) US CHARACTERISTICS OF THE partial in 40% of the population, and total SELECTED STRUCTURES- calcification represented 12, 5%.

When the thyroid cartilage was not calcified The aritenoids, when they were visualized, it presented a characteristic appearance, looked hiperechoic and homogeneous. homogeneous with a central portion slightly Generally they were explored better during hiperchogenic related to a peripheral Valsalva manoeuvers; this causes an hipoechoic band (FIG. ). In the axial plane adduccion of the vocal cords which we could see the characteristic morphology eliminates the air between the cords. The of the cartilage, as an „open book‟‟. The aritenoids appeared then one next to the quadrilateral plates were homogeneous other, symmetric and hiperechogenic. (FIG. with a thick posterior zone that gradually 2) thins toward the anterior angle. As we sweep the transducer in this plane we could As for the intrinsic muscles selected, they watch the continuity of the posterior edge could be studied in all patients. They were with the superior and inferior apophysis. We hipoechoic related to the cartilages and the could also identify how the inferior ones extrinsic muscles. Generally they did not articulated with the cricoid ring, and how the have the fibrilar appearance that is distance between this structures and the characteristic of the skeletal muscles, mucosa at this level was very thin. instead they appeared more like the the In an important percentage (80%) of the abdominal viscera muscles. For their patients the cartilage was calcified, which identification we used axial, sagital, coronal was related to the age and with different and oblique planes. pathologies. These calcifications could be The crico-thyroid muscle was identified partial (65%) or total (15%) refer to tables covering the cricoid ring. and graphics 2 and 3. Partial calcifications The vocal muscle or the thyro-aritenoid localize more often in the posterior muscle was better depicted in the segments of the quadrilateral plates and in longitudinal planes, in which we could even

Rev Imagenol, 2010, 14(1):30-36.

LARYNX ULTRASONOGRAPHY: an alternative technique in the evaluation of the aerodigestive crossroad

differentiate the two portions internal and because they depend of the moment during external, this one with a more fibrillar the respiratory cycle or even phonation. appearance. (Fig.3 and 4) The thicknesses The vocal cords were seen of the muscle as well as the vocal cord or characteristically with a pyramid shape in ventricular bands were very variable the axial plane. In its anterior portion we

7 ORIGINAL ARTICLE

could appreciate two zones, one exterior elastic cone during passive examination. hiperechogenic, which corresponds to The posterior portion of the vocal cords is cellular tissue between the cartilage and the occupied by the aritenoid cartilages which muscle. have already been described. (Fig. 3) The interior zone, hipoechoic, represents During Valsalva manoeuvers, the vocal the thyro-aritenoid muscle. We could cord closed one to each other, making neither identify the vocal ligament nor the contact by its medial edge. In that moment

Rev Imagenol, 2010, 14(1):30-36.

LARYNX ULTRASONOGRAPHY: an alternative technique in the evaluation of the aerodigestive crossroad they form a characteristic image that could see an air-artefact image that resembles a smiling face. (Fig. 6) corresponded to the Morgagni ventricle. During phonation of a long vowel “a” we (Fig. 4) could visualize, in some cases, the vibration We measured the vocal cords and of the free edge of the elastic cone; the ventricular bands obtaining this average vocal ligament, which is characteristic and results: right vocal cord medial hipoechoic reminds the vibration of a guitar string. segment 5.1mm, lateral hiperechoic The ventricular bands had in the axial plane segment 1.2mm; left vocal cord: medial a similar shape compared to the vocal hipoechoic segment 4.9mm, lateral cords, but they were hiperechogenic related hiperechoic segment 1.3mm; right and left to them. We could identify an external ventricular bands averaged 5.2mm. hipoechoic zone that we think represents The hiothyroepiglotic space, in our study, the external and superior fascicles of the was hiperechoic and homogeneous, which thyro-aritenoid muscle. We could also is probably due to its fat constitution. identify a hiperechoic external zone (as In both axial and sagital planes we seen in vocal cords) that represents the identified four levels; in the surface the level cellular tissue between the muscle and the of thyro-hyoid muscle, just below the level cartilage.

During Valsalva manoeuvers, the ventricular bands also had an adduction of the thyro-hyoid membrane, further down movement, but they did not contact as the level of the fatty tissue and in the perfectly as the vocal cords, the remaining deepest level the epiglotic cartilage. (Fig 5) air between them creates an air-artefact The size of this space was variable; in image. average we obtained the following Studying the larynx in longitudinal (coronal) measures: cephalo-caudal diameter 14mm, planes, in some patients, we could clearly transversal diameter 18mm, and antero- identify the vocal cord and the ventricular posterior diameter 10mm. band, with their differences previously The crico-thyroid space is constituted by mentioned. In this plane, between them, we the homonym muscle and membrane both

9 ORIGINAL ARTICLE previously described. In its lateral portion important anatomic and functional elements the thickness of the space decreases of the larynx. towards the crico-thyroid articulation. In the The most important advantages of US are middline we measured an average distance to complement the areas where MR and CT of 8.6mm in the sagital plane. have limitations. If we add the universal advantages of US: accessibility, economy, The calcifications often seen in the cricoid and superior spatial resolution, we could and thyroid cartilages made difficult the suggest US as an alternative and identification of the structures previously complementary imaging method in the described although it did not turned it evaluation of the larynx. impossible. Because in our series the The limitations of US depend on the calcifications more often were partial and presence and degree of calcifications in the localized in the posterior zone of the cricoid and thyroid cartilages (present in cartilages (quadrilateral plates and cricoid 80% of the population in our study). These ring) they allowed the study of the region of cartilages are the windows used for the interest. Even in the cases of partial visualization of deeper structures. However, anterior calcifications, these were patients with partial calcifications, (65% had discontinuous; the zones between the partial calcifications) allowed us to obtain calcifications presented a sufficient window important information. to assess the areas of interest. In those From our study we were able to confirm patients with total calcifications we obtained that these calcifications are more frequently a very poor evaluation, although in a few of seen in older patients who are the them, using lower frequency and harmonic population in which is more technology, we could evaluate the prevalent. We could conclude then that cartilages but not the structures behind there would be a limitation in the evaluation them. of , more prevalent in The hyoid bone was identified in all elderly patients. Nevertheless, we should patients; meanwhile, in other bones we consider the value of US in the evaluation could only assess the surface. of the hiothyroepiglotic space and the limitations that MR and CT have in DISCUSSION AND CONCLUSIONS- assessing the compromise of the thyroid and cricoid cartilages, which is of critical Larynx is a high complexity organ, both importance in the estadification of laryngeal functionally and anatomically. The cancer. evaluation of this organ requires a profound We must also consider that there are other anatomic, histological and functional laryngeal pathologies that are more knowledge. prevalent in a younger population which To perform this evaluation the clinician has could be assessed by US since in these at its disposal direct clinical and patients calcifications would not be present. laryngoscopic examination, and various Furthermore, we could add the value of US imaging methods. Although Magnetic in the evaluation of larynx functionality; this resonance (MR) and computed tomography is of great importance in some patients (i.e. (CT) are nowadays the imaging methods of singers, actors, etc). In these cases US choice, but in the evaluation of the larynx becomes a non invasive method able to they have limitations. These are related to give information that invasive ones cannot spatial resolution capability and the fact that (information of sub mucosal alterations). they perform only a static evaluation. Because of all these considerations we In our study it is shown how US is a valid conclude that US is a useful method in the method in the evaluation of the most evaluation of the larynx, and could have a

Rev Imagenol, 2010, 14(1):30-36.

LARYNX ULTRASONOGRAPHY: an alternative technique in the evaluation of the aerodigestive crossroad complementary role in the algorithm of CONSULTED BIBLIOGRAPHY laryngeal study. 1. Zappia F, Campani R.The larynx: an Links to videos- anatomical and functional echographic study. Radiol Med., 2000 Mar; 99(3):138-44. 2. Valente T, Farina R, Minelli S, Pinto A,  http://www.youtube.com/watch?v=oia Rossi G, Tecame S, Caranci F.The p5H-91O4 echographic of the larynx and the perilaryngeal structures. Radiol Med. 1996  http://www.youtube.com/watch?v=SB Mar;91(3):231-7. 09S6S_SWw 3. Reede DL, Rumancik WM, Persky M, Bergeron T. Sonographic anatomy of the  http://www.youtube.com/watch?v=K0 larynx, with particular reference to the vocal a6z_SPD7k cords. J Ultrasound Med. 1987 May;6(5):22530. 4. Murlewska A, Gryczynski M, Gadzicki M. Ultrasonic examination of the larynx. Otolaryngol Pol. 1992;46(3):238-45. 5. Werner SL, Jones RA, Emerman CL. Sographic assessment ot the epiglottis. Acad Emerg Med. 2004; 11(12):1358-60. 6. Rouviere H., Delmas A. Aparato respiratorio en Anatomía Humana, descriptiva, topográfica y funcional.; 9ª ed. Barcelona, Masson, 1998. pp. 499-514.