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Ballenger

Anatomy and Physiology ofthe LarynxClarence T. Sasaki, MD, Young-Ho Kim, MD, PhD

The human larynx is a complex organ that functions as a sphincter atthe junction of the digestive tract and respiratory tract and participatesin the diverse physiologic aspects of airway protection, respiration, andphonation. In his classic phylogenic observations, Negus allowedprioritization of the three functions of the larynx.1 In order of theirpriority, these are (1) protection of the lower airway, (2) respiration,and (3) phonation. To perform these roles, the internal and externalstructures of the larynx interact under precise neural control,producing in humans the most complex of laryngeal functions. Thus,the anatomy of the larynx reflects the specialization required by thesemultiple roles and is best understood in relation to its diversephysiologic behaviors.

ANATOMYLARYNGEAL CARTILAGESThyroid Cartilage

The thyroid cartilage is a shieldshaped structure that serves to protectthe internal anatomy of the larynx.27 It is the largest cartilage of thelarynx and is composed of two wings, the alae or laminae. The alae arefused in the midline and open posteriorly (Figure 471). In the male,the alae fuse at about 90 degrees, making a laryngeal prominence orAdams apple. In the female, this prominence is absent owing to themore oblique fusion angle of 120 degrees.Superiorly, the fusion of the alae is deficient, accounting for the thyroidnotch. Posteriorly, each ala has a superior and inferior horn or cornu.

The inferior cornu articulates with a facet on the cricoid cartilage toform the cricothyroid joint. This is a synovial joint that allows rotation

of the cricoid cartilage. This rotation varies the tension placed on thevocal folds. The superior cornu attaches to the greater cornu of thehyoid bone by way of the lateral thyrohyoid ligament. This ligamentsometimes contains small triticeal cartilages.

The two lateral thyrohyoid ligaments, along with the medianthyrohyoid ligament, are condensations of the thyrohyoid membrane;these structures attach the hyoid bone to the thyroid cartilage. At theattachment of the superior cornu to the alae of the thyroid, aprotuberance called the superior tubercle is found.About 1 cm anteriorand superior to this tubercle, the superior laryngeal artery and theinternal branch of the superior laryngeal nerve and associatedlymphatics pierce the membrane to supply the supraglottic larynx.


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At this point, transcutaneous anesthesia of the internal branch can beperformed. Running obliquely from the superior tubercle to the inferiortubercle (along the inferior margin of the thyroid cartilage) is a ridgecalled the oblique line, which serves as the attachment point for the

thyrohyoid, sternothyroid, and inferior constrictor muscles.The relationship of the surface anatomy to internal laryngeal anatomymerits consideration. Most important is the level of the true cords inrelation to the thyroid cartilage.An understanding of this relationship iscrucial to performing supraglottic laryngectomy and phonosurgery(thyroplasty type I). In this regard, the midline vertical distance fromthe thyroid notch to the inferior border of the thyroid cartilage rangesfrom 20 to 47 mm in men and 15.5 to 38 mm in women.2,3The anteriorcommissure is found at the midpoint between these landmarks. Theposterior extent of the cords is anterior to the oblique line and is foundin the middle third of this line.3

The thyroid cartilage is lined by a thick layer of perichondrium on all

surfaces except the inner surface at the anterior commissure. At thispoint are attached five ligaments, which form the scaffolding for thecorresponding laryngeal folds. From superior to inferior, they are themedian thyroepiglottic ligament (median thyrohyoid fold), bilateralvestibular ligaments (vestibular folds or false cords), and bilateral vocalligaments (vocal folds) (Figure 472, A).

The attachment of these ligaments penetrates the innerperichondrium, forming Broyles ligament. This ligament contains bloodvessels and lymphatics and constitutes an important barrier to thespread of laryngeal neoplasms.

Cricoid CartilageThe cricoid cartilage is a complete ring.27 It is theonly supporting structure that completely encircles the airway andserves as the major support for the functioning larynx. Its shape isclassically described as that of a signet ring, with the anterior archmeasuring 3 to 7 mm in height and the posterior lamina about 20 to 30mm in height.46 Its inferior border is nearly horizontal and is attachedto the first tracheal cartilage by the cricotracheal ligament.On the posterior surface of the cricoid, the posterior cricoarytenoidmuscles are attached in depressions, which are separated by a midlinevertical ridge. These muscles are the only abductors of the vocal folds.Attached to this midline vertical ridge are two fasciculi of longitudinalfibers of the esophagus. Housed on the superior surface of the

posterior cricoid lamina are the paired arytenoid cartilages. Posterior toanterior, the cricoid lamina slopes steeply downward to form theanterior cricoid arch. In the midline, between the superior portion ofthe arch and the inferior border of the thyroid cartilage, is thecricothyroid membrane. It is this structure that must be incised inperforming an emergent cricothyrotomy.

Arytenoid CartilagesThe arytenoids are paired cartilages thatarticulate with the posterosuperior portion of the cricoid cartilage.27Movement of these cartilages and their attached vocal folds allows thelarynx its often diverse and complex functions. Each arytenoid isroughly pyramidal in shape, giving it a base, an apex, and three sides.

The base of the arytenoid provides the articular facet as well as the


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muscular and vocal processes. The cricoarytenoid joint is a synovialjoint with complex movements that are somewhat debated. It appears,however, that the most important movement of the joint is a rockingmotion

of the cartilage around the long axis of its facet. Laterally, the baseforms a broad muscular process, and anteriorly, it forms the thinnervocal process. The anterolateral surface receives the vestibularligament as well as the thyroarytenoid and vocalis muscles. Theposterior surface receives muscular attachments, and to the medialsurface is attached the prominent posterior cricoarytenoid ligament.Sitting at the apex of the arytenoid is the corniculate cartilage.

Corniculate and Cuneiform CartilagesThese are small, pairedfibroelastic cartilages found in the larynx. 4The corniculate, or cartilageof Santorini, is housed on the apex of the arytenoid cartilage. Thecuneiform, or cartilage of Wrisberg, when present, is lateral to the

corniculate cartilages and is embedded in the aryepiglottic fold.Although some feel that these cartilages are vestigial, they do appearto add rigidity to the aryepiglottic fold.7This rigidity augments theimportant rampart function of these folds, thus diverting swallowedmatter laterally away from the larynx into the piriform sinuses.EpiglottisThe epiglottis is a leaf-shaped elastic fibrocartilage thatfunctions mainly as a backstop against the entrance of swallowedmatter into the laryngeal aditus.27 During swallowing, the larynx israised anterosuperiorly. This action pushes the epiglottis against thebase of the tongue, posteriorly displacing it over the laryngeal aditus.

The epiglottis has two anterior attachments. Superiorly, it is attachedto the hyoid bone by the hyoepiglottic ligament.Inferiorly at the stem or petiole, it is attached to the inner surface ofthe thyroid cartilage just above the anterior commissure by thethyroepiglottic ligament. The surface of the epiglottic cartilage hasmultiple pits and is filled with mucous glands; these pits potentiallyallow the spread of cancer from one surface of the epiglottis to theother.

The epiglottis may arbitrarily be divided into a suprahyoid and aninfrahyoid portion. The suprahyoid portion is free on both of itslaryngeal and lingual surfaces, with the laryngeal mucosal surfacebeing more adherent than the lingual. As the mucosa of the laryngealsurface is reflected back onto the base of the tongue, three folds

result: two lateral glossoepiglottic folds and a median glossoepiglotticfold. The two depressions formed by these folds are known as thevalleculae (little depression in Latin). The infrahyoid portion is free onlyon its laryngeal or posterior surface. This surface contains a smallprotuberance known as the tubercle. Between the anterior surface andthe thyrohyoid membrane and the thyroid cartilage exists a fat padwithin the preepiglottic space. Attached laterally is the quadrangularmembrane extending to the arytenoid and corniculate cartilages,constituting the aryepiglottic folds.

Ossification of Laryngeal Cartilages It has long been recognizedthat incomplete ossification of the laryngeal cartilages can be mistaken

for a foreign body on plain roentgenograms of the neck.8This


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particularly applies to ossification of the superior and inferior cornua ofthe thyroid cartilage and linear ossification of the posterior portion ofthe cricoid. Thus, the need for understanding the normal ossificationpattern of the larynx is self-evident.

It is important to realize that only those structures composed of hyalinecartilage will undergo ossification (ie, thyroid, cricoid, and arytenoidcartilages).8,9 It should be noted that the hyoid bone is completelyossified at 2 years of age and is generally not a point of radiographicconfusion. The thyroid cartilage undergoes ossification in the maleabout age 20 and in the female a few years later. Ossification beginsposteroinferiorly on the lamina. It then extends anteriorly on theinferior border and superiorly at the posterior border.At this time,nuclei of ossification can be seen in the inferior and superior cornua.

The cricoid and arytenoid cartilages undergo ossification somewhatlater than the thyroid cartilage. Ossification of the cricoid cartilagegenerally begins at the inferior border, although the superior margin of

the quadrate lamina may be an early site of ossification.Neoplastic invasion of the laryngeal cartilages generally takes place inthe ossified portion of the cartilage.10The incomplete ossificationpattern may make it difficult to appreciate small areas of invasion.

ELASTIC TISSUESThe elastic tissue of the larynx consists of two main parts: (1) thequadrangular membrane of the supraglottic larynx and (2) the thickerconus elasticus and vocal ligaments of the glottic and infraglotticlarynx. The quadrangular membrane attaches anteriorly to the lateralmargin of the epiglottis and curves posteriorly to attach to thearytenoid and corniculate cartilages. This structure and the overlyingmucosa constitute the aryepiglottic folds. Each fold forms part of themedial wall of each piriform sinus. The inferior edge of thequadrangular membrane constitutes the vestibular ligaments. Theconus elasticus is a thicker elastic structure than the quadrangularmembrane. It attaches inferiorly at the superior border of the cricoidcartilage. It then projects upward and medial to its superiorattachments, the anterior commissure of the thyroid cartilage and thevocal process of the arytenoid.Between these superior attachments, the conus thickens to form thevocal ligament.Anteriorly, the conus forms the cricothyroid membrane,and in the midline, this membrane condenses to form the cricothyroid

ligament (Figures 471 to 473). The superior extension of the conus(thyroglottic membrane) parallels the superior surface of the true cord.Because it may normally be incomplete, it forms an imperfect barrierto the inferior extension of the transglottic cancers (Figure 474).7

MUSCLESExtrinsic MusclesThe extrinsic muscles of the larynx are thosemuscles of the laryngohyoid complex that serve to raise, lower, orstabilize the larynx. 27Those muscles that elevate the larynx are thethyrohyoid, stylohyoid, digastric, geniohyoid, mylohyoid, andstylopharyngeus. These muscles are important in the elevation and

anterior displacement of the larynx during swallowing. They also help


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to suspend the larynx, via the hyoid bone, from the skull base andmandible. The principal depressors of the larynx are the omohyoid,sternothyroid, and sternohyoid. These muscles displace the larynxdownward during inspiration. The middle constrictor, inferior

constrictor, and cricopharyngeus muscles are also important extrinsiclaryngeal muscles. The proper functioning of these muscles is crucial tothe precisely timed swallowing reflex.

Intrinsic MusclesThe intrinsic muscles of the larynx are thosemuscles that are anatomically restricted to the larynx proper. Theymodify the size of the glottic opening along with the length and tensionon the vocal folds. They consist of multiple adductors but only a singleabductor. With the exception of the interarytenoid, the intrinsicmuscles are paired, and these paired muscles appear to actsynchronously (Figure 475).

CRICOTHYROIDMUSCLE.The cricothyroid muscle is located on theexternal surface of the laryngeal cartilages. It is classically describedas consisting of two bellies. The straight portion or pars recta attachesthe lateral portion of the anterior arch of the cricoid cartilage to theinferior border of the thyroid cartilage in a fairly vertical direction. Thesecond belly, the pars obliqua, also from the anterolateral border of thecricoid arch, travels obliquely upward to insert on the anterior portionof the inferior cornu. When the right and left cricothyroid musclescontract, they rotate the cricoid at the cricothyroid joint. This actionbrings the anterior arch of the cricoid superiorly toward the inferiorborder of the thyroid laminae while displacing the posterior cricoidlamina (and the arytenoid cartilages) inferiorly.

This inferior displacement increases the distance between the vocalprocesses and the anterior commissure; the result of this action is tolower, stretch, and thin the vocal folds while bringing them into aparamedian position. The stretching of the vocal fold also sharpens theedge of the vocal fold and passively stiffens the component layers ofthe vocal fold (Figure 476). Biomechanically, this translates into ahigher fundamental frequency produced by the vocal folds.

POSTERIOR CRICOARYTENOIDMUSCLE.This muscle is the sole abductor ofthe vocal folds. It is seated in a depression on the posterior surface ofthe cricoid lamina, and its fibers run obliquely superior and lateral to

attach onto the muscular process of the arytenoid cartilage. It iscomposed of two compartments: horizontal and vertical bellies.Contraction of these fibers brings the muscular process medial,posterior, and inferior while laterally rotating and elevating the vocalprocess. This action abducts, elongates, and thins the vocal folds whilecausing the vocal fold edge to be rounded. The stretching of the vocalfold leads to passive stiffening of its layers. The complex function ofthis muscle has been studied in the canine in which three distinctneuromuscular compartments are found. It is proposed that thevertical and oblique bellies normally cause vocal fold abduction duringrespiration, whereas the horizontal belly is primarily used to adjust theposition of the vocal process during phonation.11,12


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LATERAL CRICOARYTENOIDMUSCLE.This is the main antagonist of theposterior cricoarytenoid. It attaches along the superior border of thecricoid cartilage and then sends its fibers posteriorly to insert on theanterior portion of the muscular process. Contraction of this muscle

brings the muscular process anterolaterally while adducting andlowering the vocal process. This results in adduction, elongation, andthinning of the vocal folds. The edge of the vocal fold becomessharper, and its component layers are passively stiffened.

INTERARYTENOID/ARYEPIGLOTTICMUSCLE.The interarytenoid is the onlyunpaired intrinsic muscle, consisting of two types of muscle fibers. Thebulk of the muscle consists of transverse fibers passing from theposterior surface of one arytenoid cartilage to the posterior surface ofthe other. This muscle contracts to bring together the arytenoidcartilages, thus assisting in closing the posterior portion of the glottis.

This does not significantly affect the mechanical properties of the vocal

folds. Along with these transverse fibers are oblique fibers. Theseoblique fibers pass from the posterior portion of the arytenoid on oneside to the apex of the arytenoid on the other side, thus crossing in themidline.Some fibers insert at the apex, whereas others travel along thequadrangular membrane. These fibers contract to narrow the laryngealaditus. Those fibers traveling along the quadrangular membrane (thusthe aryepiglottic fold) constitute the aryepiglottic muscle.

THYROARYTENOIDMUSCLE.This muscle is classically divided into thethyroarytenoid internus and externus. These have the sameattachments, but the internus lies deep or internal to the externus. Inaddition, the internus is more well developed than the externus. Thethyroarytenoid externus arises from the anterior commissure andinserts onto the lateral surface of the arytenoid cartilage. It contractsto bring the vocal process and anterior commissure closer to eachother, thus adducting the vocal folds. It also contracts to adduct thefalse cords. The externus sends a few slips of muscle fibers onto thequadrangular membrane to establish the thyroepiglottic muscle. Thismuscle, like the aryepiglottic muscle, acts to narrow the laryngeal inlet.

The thyroarytenoid internus or vocalis muscle attaches at the anteriorcommissure and inserts onto the vocal process, sending a few slips offibers below the vocal ligament onto the conus elasticus. It contracts to

adduct, shorten, thicken, and lower the vocal fold while rounding itsedge. The body (muscle) of the vocal fold is actively stiffened, whereasthe cover is passively slackened. Recently, immunohistochemicalstaining for myofibrillar adenosine triphosphatase reveals that

INTERNAL ANATOMYThe internal anatomy of the larynx consists of three compartmentsseparated by two folds (see Figure 473).27The three compartmentsare the vestibule, ventricle, and infraglottic cavity. The false and truevocal folds separate the above compartments. These mucosa-linedcompartments demarcate two spaces of importance: the preepiglotticspace and the paraglottic space.


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Vestibule A laryngoscopic view of the larynx reveals the vestibule asthat portion of the larynx from the tip of the epiglottis to the false orvestibular folds. Thus, the vestibule is bound by the epiglottisanteriorly, the aryepiglottic folds laterally, and the arytenoid and

corniculate cartilages with the interarytenoid muscle posteriorly. In thelaryngoscopic view, the anterior commissure is frequently hidden bythe protuberance of the epiglottis known as the tubercle.As previously discussed, the vestibular folds are formed by mucosaoverlying the vestibular ligament (inferior border of the quadrangularmembrane). The submucosa of the ventricle contains numerousseromucinous glands. The secretions produced by these exocrineglands provide both mechanical and immune (lysozyme) protection forthe vocal folds.15VentricleThe ventricle or sinus of Morgagni is the small spacebetween the false and true vocal folds. The ventricle is often hiddenduring laryngoscopic examination of the larynx unless exposed by

lateralization of the false vocal fold. At the anterior end of the ventricleis a diverticulum known as the laryngeal saccule. The saccule (ofHilton) is lined with mucous glands, which are thought to lubricate thevocal folds. Fibers of the thyroarytenoid muscle line the walls of thesaccule and are thought to express mucus from the saccule when theycontract. The size of the saccule is quite variable; however, it seldomextends above the superior border of the thyroid cartilage. Abnormaldilatation of the saccule results in an air-filled laryngocele that shouldbe distinguished from a mucocele of the saccule (saccular cyst), whichlacks free communication with the ventricle and thus is not air filled.16

The vocal folds that form the inferior boundary of the ventricle aredescribed in more detail in a separate section.

Infraglottic CavityThe infraglottic cavity extends from the glottisdown to the inferior border of the cricoid cartilage. Its lateral boundaryis formed by the conus elasticus and walls of the cricoid cartilage.Piriform Sinus Although the piriform sinus is anatomically part of thehypopharynx, understanding its anatomy and its relationship to thelarynx is essential. The piriform sinus is a gutter formed by thearyepiglottic fold, arytenoid, and superior cricoid medially and thethyrohyoid membrane and internal surface of the thyroid laminalaterally. Superiorly, it begins at the lateral glossoepiglottic fold.Inferiorly, the apex of the sinus blends with the esophageal inlet at

about the superior border of the cricoid (Figure 477). Thus, cancerinvasion of the apex implies the necessity of removing a portion of thecricoid if conservation laryngectomy is planned.7

There are two important markings within the piriform sinus. Anteriorlyin the floor of the sinus, a small fold can be seen, which marks thecourse of the superior laryngeal nerve. This submucosal course of thenerve makes it possible to anesthetize the nerve topically in thepiriform sinus. The second, more variable landmark is the protrusionmade into the sinus from the superior cornu of the thyroid cartilage.

This smooth protrusion, which usually presents in the elderly, shouldnot be confused with neoplasm.


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MucosaThe mucosa of the larynx is of two types: pseudostratifiedciliated columnar cell (respiratory) epithelium and squamous cellepithelium. Much of the larynx is surfaced by respiratory epithelium;however, the superior portion of the epiglottis, upper portions of the

aryepiglottic folds, and free edges of the vocal folds are surfaced bysquamous cell epithelium. Beneath this covering epithelium is avariable basement membrane, and separating these two is a layer ofloose fibrous stroma. It should be noted that this loose fibrous layer isabsent on the true vocal folds as well as the laryngeal (posterior)surface of the epiglottis. The absence of this layer on the posteriorsurface of the epiglottis accounts for the more intense swelling of thelingual (anterior) surface of the epiglottis in inflammatory conditions ofthe larynx.

Preepiglottic SpaceThe preepiglottic space, as its name implies, liesanterior to the epiglottis, which serves as its posterior boundary. It is

bound superiorly by the hyoepiglottic ligament and mucosa of thevalleculae and inferiorly by the thyroepiglottic ligament. The anteriorboundaries are the thyrohyoid membrane and the inner surfaces of thethyroid laminae. Laterally, the preepiglottic space opens in theparaglottic spaces. Cancer on the infrahyoid portion of the epiglottiscan penetrate this structure and gain access to the preepiglottic space.

Paraglottic Space A paraglottic space, as its name implies, lies oneach side of the glottis. This space lies above and below the true andfalse vocal folds and is important in the transglottic and extralaryngealspread of neoplasms.Medially, the space is bound by the quadrangularmembrane, ventricle, and conus elasticus. Laterally, it is bound by theperichondrium of the thyroid lamina and the cricothyroid membrane.Anterosuperiorly, the space opens in the posterior portion of thepreepiglottic space. The mucosa of the piriform sinus forms theposterior boundary. The relationships of this paraglottic space make itimportant in considering the spread of laryngeal cancer. Supraglotticcancer invading into this space may quickly extend extralaryngeally.

VOCAL FOLDSThe anatomy of the vocal folds is complex and is thus consideredseparately. The vocal fold is considered the structure between thevocal process of the arytenoid and the anterior commissure. The vocal

folds and the slit between them (rima glottidis) constitute the glottis.The glottis can be divided by a horizontal line between the tips of thevocal processes. This imaginary line divides the glottis into anintermembranous portion and an intercartilaginous portion. Theanterior to posterior (length) ratio of the intermembranous portion tothe intercartilaginous is 3 to 2; however, the ratio of cross-sectionalareas defined by them is 2 to 3. Thus, owing to its more rectangularshape, the intercartilaginous portion is larger.Some have called this the respiratory portion of the rima.4,17Themembranous or vibratory portion of the vocal folds consists of threewell-defined structural layers. From superficial to deep, they are theepithelium, lamina propria (three layers), and vocalis muscle. Hiranodivided these layers according to a body-cover concept (see Figure 47


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6, A).17The cover consists of the overlying epithelium and thegelatinous superficial layer of the lamina propria. The body consists ofthe vocalis muscle, which he likened to thick rubber bands. Betweenthese exists a transition zone composed of the intermediate (elastic)

and deep (collagenous) layers of the lamina propria.According to this concept, the vocal folds consist of a multilayeredvibrator with increasing stiffness from the cover to the body. Thus, thecover is responsible for most of the vibratory action of the vocal folds.At the anterior and posterior ends of the vocal folds exists an anteriorand a posterior macula flava, respectively. These are essentially athickening of the intermediate (elastic) layer of the lamina propria andare thought to function as cushions protecting the ends of the vocalfolds from vibratory damage. It should be noted that the same body-cover concept does not apply to the larynx of children because of themore homogeneous nature of the lamina propria.It is not until nearly the end of adolescence that the lamina matures

into its adult form. In the senile larynx, the elastic layer and the vocalismuscle tend to atrophy, whereas the collagenous layer thickens. Thecover becomes thickened and edematous secondary to changes in thesuperficial layer of the lamina, whereas the epithelium itself changeslittle. The shape of the true and false vocal folds carries biomechanicalsignificance.When seen in coronal section, both appear as valve-likestructures, with the leaflets of the false folds pointing inferiorly andthose of the true folds pointing superiorly (see Figure 473). Thus, thefalse folds passively impede egress of air, whereas the true foldsimpede its ingress.Work- ing with cadaver larynges, Brunton and Cashdemonstrated that the false folds offered a resistance equaling 30 mmHg to the egress of air from below, whereas the true folds offered aresistance equaling 140 mm Hg to the ingress of air from above.18 Bothstructures offered little resistance to the opposite flow of air (ie, theyact as one-way valves).

VESSELSArteries and VeinsThe arterial supply to the larynx consists of thesuperior and inferior laryngeal arteries.27 After the superior thyroidartery branches off the external carotid, it courses lateral to thelaryngohyoid complex and gives off the superior laryngeal artery atapproximately the level of the hyoid bone. This artery then runsanteromedially with the internal branch of the superior laryngeal nerveto enter the thyrohyoid membrane inferior to the nerve. It then enters

the submucosa of the piriform sinus and is distributed to intralaryngealstructures. The superior thyroid also gives off a cricothyroid branchthat courses horizontally below the thyroid cartilage. The inferiorlaryngeal artery is a branch of the inferior thyroid artery that comes offthe thyrocervical trunk branching from the subclavian artery. Aftercoursing posterior to the cricothyroid joint with the recurrent laryngealnerve, the artery enters the larynx by passing through a gap in theinferior constrictor muscle known as the Killian-Jamieson area. Theartery is then distributed to the remainder of the internal larynx,making multiple anastomoses with the superior laryngeal artery. Thevenous supply parallels the arterial supply.


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Lymphatics An appreciation of the lymphatics of the larynx isprerequisite to understanding the spread of cancer of the larynx, aswell as the operative procedures designed to eradicate the disease.27,19The lymphatics of the larynx are divided into superficial

(intramucosal) and deep (submucosal) groups. The deep network isfurther divided into right and left halves, with little communicationbetween them. These two halves can be further divided intosupraglottic, glottic, and subglottic, with special consideration given tothe ventricle in the supraglottic region. Although the superficialnetwork is richly anastomotic throughout the larynx, it is the deepnetwork that is important in the spread of cancer and will be givenfurther consideration. The drainage of the supraglottic structures(aryepiglottic folds and false cords) follows the superior laryngeal andsuperior thyroid vessels. Thus, the lymphatics flow from the piriformsinus through the thyrohyoid membrane to end primarily in the deep

jugular chain around the carotid bifurcation. It should be noted that the

epiglottis is a midline structure; thus, its lymphatic drainage isbilateral. The lymphatic drainage of the ventricle is different from theother supraglottic structures. Dye injected into the ventricle enters theparaglottic space and is quickly spread by the lymphatic systemthrough the cricothyroid membrane and also into the ipsilateral lobe ofthe thyroid (justifying its resection in laryngectomy). The true vocalfolds are devoid of lymphatics, accounting for the high curability ofcancer localized to this structure. The subglottic larynx has twolymphatic drainage systems. One system follows the inferior thyroidvessels to end in the lower portion of the deep jugular chain as well asthe subclavian, paratracheal, and tracheoesophageal chains. The othersystem pierces the cricothyroid membrane. This system appears toreceive lymphatics from both sides of the larynx and disseminatebilaterally to the middle deep cervical nodes as well as theprelaryngeal (Delphian) nodes.

PHYSIOLOGYAs previously stated, the three functions of the larynx in order ofpriority are (1) protection of the lower airway, (2) respiration, and (3)phonation.1 A flawless performance of these functions requires anintact neuromuscular system to respond to both volitional and reflexsignals presented to the larynx.

INNERVATIONThe pattern of innervation to and from the larynx and the type anddistribution of its receptors determine the functional capabilities of thelarynx. The larynx is innervated by the superior and inferior laryngealnerves. The superior laryngeal nerve leaves the nodose ganglion topass between the carotid artery and the laryngohyoid complex. Itdivides into a larger internal and smaller external branch. The internalbranch pierces the thyrohyoid membrane with the superior laryngealartery and becomes the

NEUROPHYSIOLOGY OF PROTECTIVE

FUNCTION


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The glottic closure reflex is a polysynaptic reflex that allows the larynxto protect the lower airway from penetration and aspiration. However,when exaggerated, this reflex accounts for the production oflaryngospasm. Protective closure of the larynx occurs in three tiers. In

the first tier, the laryngeal inlet is contracted by collapsing thearyepiglottic folds medially. The anterior and posterior gaps are filledby the epiglottic tubercle and the arytenoid cartilages, respectively. Inthe second tier, the false vocal folds are brought together. The finaland most important tier occurs at the level of the true vocal folds.Because the valvular action of the true vocal folds resists ingress ofmaterial, they offer the most important level of protection.It should be noted that it is the thyroarytenoid or slips from this musclethat contract at each level of closure. This muscle is one of the fastestcontracting of all striated muscles in the body. Classically, the afferentlimb of this reflex occurs through stimulation of touch, chemical, orthermal receptors in the supraglottic larynx.26

Laryngospasm occurs when stimulation of the superior laryngeal nerveleads to a prolonged adductor response. This response is maintainedwell after the initiating stimulus is removed, and section of the superiorlaryngeal nerves abolishes the response. Clinically, this is typicallyseen in the setting of endotracheal intubation/extubation or aftermanipulation of the airway, especially if blood has contaminated thelaryngeal inlet. The response is dampened in the face of barbiturates,hypercapnia, positive intrathoracic pressure, and severe hypoxia.27Although not classically considered part of the protective reflex, reflexswallowing from stimulation of the superior laryngeal nerve may haveprotective functions. It has been shown that reflex swallowing occurswith application of hypotonic fluids to the supraglottic larynx,particularly the laryngeal surface of the epiglottis, glottis, and internallarynx. Although this is not the normal mechanism to initiateswallowing, it may serve to protect the larynx against fluid that entersthe laryngeal inlet.20

NEUROPHYSIOLOGY OF RESPIRATORYFUNCTIONIt is intuitive that if the larynx is the sphincter to the lower airway, forrespiration to occur, the sphincter needs to be actively opened duringinspiration. Also, the opening of the folds must be synchronous with,but slightly precede, the descent of the diaphragm. Through the workof many individuals, this observation is well supported.24,28,29The

respiratory center of the medulla, with the help of higher centralnervous system and peripheral input, maintains eupneic respiration. Itdrives the synchronous opening of the glottis and descent of thediaphragmduring inspiration. The opening of the glottis is primarilythrough the action of the posterior cricoarytenoid. However, inhyperpneic conditions, the cricothyroid contracts rhythmically with theposterior cricoarytenoid.28,29The contraction of both of these musclesincreases the glottic aperture in both anteroposterior and horizontaldimensions. During phonation, the cricothyroid lengthens and passivelyadducts the vocal folds. However, during respiration, when contractedin concert with the posterior cricoarytenoid, the effect is to lengthenthe open glottis, thus increasing the cross-sectional area for airflow.


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Understanding the role that the cricothyroid plays as an accessorymuscle of inspiration underlies the rationale for superior laryngealnerve section in the face of bilateral recurrent laryngeal nerveparalysis. Bilateral paralysis produces dyspnea, which will lead to

cricothyroid contraction, further adducting the paralyzed folds.Unilateral superior laryngeal nerve section reduces glottic resistanceby preventing its full adduction. The rhythmicity of the phrenic nerveand the posterior cricoarytenoid can be increased by hypercapnia andventilatory obstruction. It is lessened by hypocapnia. The effect ofventilatory resistance on posterior cricoarytenoid activity has beenextensively studied in the canine model. In this model, whenventilatory resistance is eliminated, so is the reflex abductor activity ofthe posterior cricoarytenoid. It is felt that the afferent limb of this reflexresides within the ascending vagus nerve and that the end-organreceptors are located within the thorax, although their precise locationis unknown. The longer abductor activity is lost, the more difficult it is

to re-establish.30This is the rationale for downsizing tracheotomy tubes(thus gradually increasing ventilatory load) prior to decannulation.

The role of the larynx in controlling expiration must also be considered.It is well known that the control of respiratory rate occurs primarilythrough variation of the expiratory phase. The time of expiration isdependent on the ventilatory resistance produced by the glottis.Asdiscussed above, the cricothyroid contracting with the posteriorcricoarytenoid will give the maximal glottic opening and hence thelowest ventilatory resistance. In this regard, cricothyroid contractionduring expiration occurs when the critical subglottic pressure change of30 cm H2O/s is exceeded and continues as long as positive subglotticpressure is maintained. As expected, this threshold for activation isreduced in hypercapnia (allowing for quicker expiration and a fasterrespiratory rate) and increased in hypocapnia.31

NEUROPHYSIOLOGY OF PHONATIONThe complex mechanisms of phonatory control coordinate central andperipheral components. Electromyographic investigation of the controlof peripheral neuromuscular systems involved in phonation hasdemonstrated specific intrinsic and extrinsic muscle function inhumans. Central mechanisms are less well understood and often relyon animal models, which may only infer function in the uniquephonatory systems of the human. As a general model, the larynx, as asystem, must respond to central commands from linguistic and motorcenters. Signals are then relayed to the motor cortex in the precentralgyrus and on to motor nuclei in the brainstem and spinal cord. Thesesignals are transmitted to the respiratory, laryngeal, and articulatorymuscles responsible for speech and voice production. These messagesare influenced by the extrapyramidal system, including the cerebralcortex, cerebellum, and basal ganglia, exerting fine control ofrespiration, phonation, and articulation.32Specific connectivity and the central control of brainstem motorneurons responsible for voluntary control of phonation remain illusive.Laryngeal reflexes, which are key to the coordination of respiration,phonation, and deglutition, are understood primarily from the research

focused on respiration and deglutition.20 Further, central projections to


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laryngeal mechanisms are not consistent across species and may differfrom nonhuman primates to humans as well. The nucleus tractussolitarius (NTS), periaqueductal gray, parabrachial nucleus, locuscaeruleus, and ventromedial nucleus of the thalamus are all areas

anatomically associated with the laryngeal system.20

Figure 478 illustrates branching of the superior laryngeal nerve withcentral connectivity and projections of the NTS. However, specificmechanisms of control are not well defined. In some cases, the centralterminations of specific sensory receptors and the origin of themotoneuron fibers are known, as in somatotopic organization for theface and limbs. To date, studies of the role of the cerebral cortex inphonation in primates reveal no such individual muscle representationor somatotopic mapping of the laryngeal system.20The role ofperipheral mechanisms in phonatory control has been studied moresuccessfully using electromyography, airflow, and pressure studies inthe vocal tract as well as imaging techniques, which allow observation

of the vocal tract during phonatory postures. It is important to considerthat phonation takes place in concert with upper articulators, the lip,tongue, jaw, and velum.Mechanical tissue deformation and, in particular, the pull of the upperarticulators on the larynx via the laryngeal-hyoid complex necessarilyinfluence the phonatory environment. For example, Figure 479illustrates vocal tract shaping for four distinct vowels.Note theapparent pull of the tongue high and forward for production of /i/(labeled iy), in contrast to posterior and low posture for /a/ (labeledaa). The consequent constriction or, conversely, the opening of theposterior pharynx plays a key role in the acoustics of sound producedfor each of these postures and influences laryngeal posturing forphonation.33Electromyographic studies of specific muscle functionindicate firing rates uniquely suited for fine control of laryngealfunction. Contraction times for the intrinsic muscles in several speciesare presented in Table 471. Further, the high innervation ratio forhuman laryngeal muscles, estimated at 100 to 200 cells per motorunit,34 makes laryngeal muscles capable of a great degree of precisecontrol as required for adjustment of speaking frequency and intensity.Intrinsic and extrinsic musculature, described previously in thischapter, influence specific action of laryngeal muscles duringphonatory shaping of the glottis in sound production as described byHirano (see Figure 475).32Table 472 summarizes the influence of

each of these muscles on the shape and tension of the glottis duringphonation. It has been shown that the laryngeal muscles start tocontract about 100 to 200 ms prior to the onset of phonation.35 Further,the most important muscle in varying the phonation style (fromhypotense to hypertense) is the thyroarytenoid muscle. 36Thefrequency of vibration depends on the following: (1) vibratory mass ofboth vocal folds, (2) the anterior to posterior tension, (3) functionaldamping at high pitch, and (4) subglottic pressure. In this regard, Gayand associates showed that in the chest register, the cricothyroid andvocalis, with the possible contribution of the posterior cricoarytenoid,most consistently control changes in fundamental frequency.37Lovquist and others later described electromyographic recordings

obtained from four intrinsic laryngeal muscles with simultaneous


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transillumination and acoustic signals.38The vocalis and lateralcricoarytenoid muscles were observed to participate in the control ofboth articulation and phonation. The interarytenoid muscle appearedto be involved only in articulatory adjustments. Activity in the

cricothyroid was primarily related to changes in fundamentalfrequency. This muscle also showed an increase in activity for voicelesssounds. In addition, the vocalis muscle appeared to participate inglottal adduction without complete closure in voiceless clusteredsounds, with the lateral cricoarytenoid and the interarytenoid playingno particular roles. Studies such as these underscore the complexinteractive nature of laryngeal musculature in phonatory/articulatoryinteraction. In considering the phonatory process, a variety of factorsnecessarily contribute to the acoustic product as defined in Table 473.

The psychoacoustic parameters of pitch, loudness, quality, andfluctuation are correlated with acoustic qualities of fundamentalfrequency, amplitude, waveform, and acoustic spectrum. High-speed

photography and observation of vocal fold vibration viavideostroboscopic endoscopy reveal much about the behavior of theglottis during phonation.32,39

The vibrations of the vocal folds are a passive phenomenon andrepresent the basis of the aerodynamic theory of sound production.Vibration of the vocal folds changes DC airflow into AC airflow,converting aerodynamic energy to acoustic energy. The mucosal waveproduced by these vibrations has been captured on ultrahigh-speedphotography by Hirano.32The vibratory cycle is described as havingthree phases: opening, closing, and closed. By convention, the cycle isdescribed as beginning with the vocal folds closed. Frames 1 to 5 (seeFigure 476, B) represent the opening phase. During this phase,subglottic pressure increases, forcing the vocal folds apart from aninferior to superior direction until the glottis opens, letting air escapeand thus releasing subglottic pressure. As the elastic recoil of the vocalfolds forces them back together, the portion of the vocal fold that wasthe last to open (superior portion)is the last to close. Thus, the vocalfolds close from inferior to superior (frames 6 to 8). The folds thenremain closed until the subglottic pressure builds up enough to forcethem open again. Anatomically, the movement of the mucosal wavedepends on the soft and compliant lamina propria and a healthylayered structure. In extracting complex details of glottal areawaveforms from videostrobolaryngoscopic recordings using modern

computers and software (Figure 4710), Woo demonstrated male andfemale differences as well as influences of pitch and loudness.39Women commonly demonstrate small posterior glottal gaps that seemto have no pathologic acoustic significance, whereas their glottalcycles have shorter closed phases than those of men. Mean peakglottal area is smaller in women, not only because of their smalleranatomic size but also owing to the fact that their higher frequency ofvibration limits the lateral excursion of the vocal folds, therebyreducing the amplitude of vibration. As intensity increases, the closingphase becomes shorter and the closed period becomes longer,suggesting that the closing patterns of vocal folds are an especiallyimportant feature in normal and pathologic phonation. The

coordination of higher cortical centers interacts with specific


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musculature in the vocal tract to produce acoustic products recognizedas speech. The laryngeal contribution to this product continues to berevealed in basic studies of phonation as an interactive process.


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Trauma to the LarynxPeak Woo, MD, Philip Passalaqua, MD

ETIOLOGYThe position of the larynx in the neck, protected by the mandiblesuperiorly and the clavicles and sternum below, shields it from falls andblows. The lateral mobility of the larynx within the neck also serves toprevent the severe effects of compression injuries. The ossificationcenters of the larynx do not develop until young adulthood and aremore pronounced in the male. This makes laryngeal fractures a rarecondition, one more often seen in men than in women. Although thecartilaginous framework provides protection to the larynx, once thisframework has been violated by trauma, the tight space defined by thelaryngeal skeleton makes rapid airway compromise possible. The tight

adherence of the soft tissue to the laryngeal framework and thepotential spaces that can be easily expanded at the expense of theairway make rapid changes in the airway status possible in patientswith laryngeal trauma.External laryngeal trauma is a relatively uncommon injury. Jewett et alreported an incidence of blunt trauma to the larynx of 1 in 137,000 inan analysis of 54 million inpatients over a 5-year period in 11 USstates.1 Laryngeal trauma accounts for about 1 in every 25,000emergency department visits. In addition to the obvious possibility ofacute airway obstruction, the complications of late diagnosed orundiagnosed laryngeal injuries can be severe, including glotticinsufficiency, aspiration, and laryngeal stenosis. Furthermore, studies

have demonstrated that early diagnosis and surgical managementresult in improved functional outcomes.1,2

BIOMECHANICS OF LARYNGEAL TRAUMAThe larynx may be injured by blunt and penetrating wounds and maybe traumatized by intubation and foreign bodies. In motor vehicletrauma, the head is often in extension. During deceleration, the larynxand neck are pulled forward while the thorax is held in restraint. Thelarynx is decelerated against blunt objects, such as the steering wheeland dashboard, and is crushed against the vertebral column. Similarmechanisms of injury may occur in sporting accidents (ie, karate,

hockey, basketball, Frisbee throwing, water skiing). In laryngealtrauma, the severity of the injury is dependent on the velocity and siteof injury. In mild cases, the patient may not report the injury for manydays. Severe injuries may result in catastrophic asphyxia in the field.

The other major causes of blunt trauma to the larynx are of theclothesline type. The injury may be caused by a clothesline, chain, ortree branch. Injures of this type occur when the anterior part of theneck strikes one of these objects while bicycling, snowmobiling, orriding in all terrain vehicles. Clothesline injuries tend to be more severebecause of the high impact of the force and therefore require specialattention. In clothesline injuries, the possibility of cricotrachealseparation is a special concern. It appears that the larynx cannot befractured by concussion unless it is supported to some extent by the


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vertebral column. Furthermore, a blow to the neck will do relativelylittle damage to the laryngeal skeleton if the laryngeal cartilage is softand pliable.

The cartilage may spring back into position without fracture. Such

injury will result in soft tissue edema and hematoma. Soft tissuedisruption may result in edema and hematoma severe enough tointerrupt the airway or cause dysphonia and stridor. Rapid accelerationand deceleration of the soft tissue of the larynx may result in arytenoidcartilage dislocation and mucous membrane tears and disruption of thelaryngeal ligaments.

TYPES OF LARYNGEAL TRAUMASoft tissue injuries to the larynx from blunt trauma include laryngealedema, hematoma, and mucosal tears. Often edema or hematomainvolves the aryepiglottic folds and false vocal cords owing to thesupraglottic submucosal distensibility.3 Fluid or blood accumulations

can occur rapidly, resulting in acute laryngeal obstruction. During thecourse of a laryngeal trauma, the posterior ends of the thyroidcartilage alae may be compressed against the vertebral column. Thispressure against the thyroid cartilage will splay the angle of the thyroidcartilage to a more obtuse angle. Therefore, most fractures of thethyroid cartilage occur in the midline with loss of the normal acuteangulation of the thyroid alae (Figure 511). A similar force applied tothe cricoid cartilage against the vertebral column will result in acomminuted fracture of the signet ringshaped cartilage.Most blunt injuries resulting in laryngeal trauma are caused by ananterior to posterior striking force. In strangulation injuries, the larynxmay be injured by lateral to medial compressive forces. It is likely thatbecause of the greater ossification of the cartilages and the greaterdevelopment in both acute thyroid alae angulation and size, the malelarynx is more brittle and more subject to fracture under the influenceof violent impact. Because of the prominence of the thyroid cartilageand its thyroid notch, it is the cartilage most usually fractured. Thecricoid cartilage is generally more protected. With the exception ofisolated trauma to the lower part of the neck by a thin object, cricoidfractures are usually combined with thyroid fractures.When cricoidfractures are combined with thyroid cartilage fractures, they areusually more extensive and dangerous. A wide array of fractures,dislocations, and nerve injuries are also possible. Table 511 lists the

various fractures and other trauma possible.Gunshot and knife wounds account for the majority of penetratinginjuries. Gunshot wounds produce a greater degree of soft tissue injurydepending on the velocity and mass of the bullet. The higher-velocitybullets will result in greater injury to the surrounding soft tissues. Knifeinjuries usually result in less soft tissue damage but can be associatedwith injuries of vessels and nerves at some distance from the wound ofentrance. During a knife injury, the larynx is often displaced withoutserious injury owing to the great lateral movement. A slash to the neckmay result in lacerations of the cricothyroid membrane. Penetratinginjuries of the larynx and trachea may occur in isolation but are usuallypart of more complex penetrating neck trauma that requires greaterworkup.


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Laryngeal trauma in children tends to be less severe because of thehigher position of the larynx in the neck in the pediatric population.Furthermore, owing to the pliable cartilage of a childs larynx, there isa lower incidence of laryngeal fractures. In addition, there is a lower

incidence of laryngotracheal separation in the pediatric populationbecause of the narrow cricothyroid membrane.4 Intubation injuries tothe larynx usually result in soft tissue trauma to the posterior part ofthe larynx caused by an endotracheal tube or cuff. The most commonoccurrence is ulceration of the mucous membrane overlying the vocalprocess of the arytenoid cartilage. More severe injuries may be causedby prolonged intubations. These may take the form of intubationgranuloma, posterior synechia, glottic stenosis (Figure 512),cricoarytenoid joint ankylosis, and subglottic stenosis. The factorscontributing to poor outcomes in intubated patients include prolongedintubation, infection, gastroesophageal reflux, movement, pressurenecrosis, and chondritis. The arytenoid cartilage can be dislocated by

traction of the endotracheal tube that can cause a tear of the posteriorcricoarytenoid ligament. In addition, an endotracheal tube pushed intothe larynx without direct guidance through the glottis may result in aposterior vector against the cricoarytenoid joint, resulting in aposterior, lateral dislocation of the arytenoid cartilage. This may beassociated with a tear of the anterior cricoarytenoid ligament.

DIAGNOSISThe symptoms and signs depend on the cartilage involved and theextent of the soft tissue injury. Patients with laryngeal trauma maypresent to the emergency department with multiple injuries to other

organ systems. Therefore, the laryngeal injury that has not causedacute airway obstruction may be missed. One should have a high indexof suspicion for laryngeal injury in any patient presenting with bluntneck trauma. Diagnosis of subtle laryngeal injury in a timely manner isimportant for both treatment and prognosis. All patients with injury tothe anterior part of the neck should be carefully evaluated for theexistence of laryngeal trauma. The symptoms suggestive of laryngealinjury include cough and expectoration. Pain is present in nearly everypatient with laryngeal injury and is accentuated by phonation ordeglutition. Tenderness and swelling may be quite marked. Swelling ofthe neck may be accompanied by loss of laryngeal landmarks in theanterior part of the neck.

Dyspnea is often present in varying degrees owing to edema of the softtissue or blood in the trachea. Hemoptysis may be present but isusually not severe. Stridor and voice change are other signs thatsuggest laryngeal trauma. Although dysphagia may be present withendolaryngeal trauma, it may also be suggestive of esophageal orhypopharyngeal injury. Emphysema of the neck suggests a perforationof a viscus such as the larynx or hypopharynx. Soft tissue injuries maybe accompanied by ecchymosis of the skin. In more severe injuries ofthe larynx in which the airway compromise is marked, sphyxiation andmassive hemoptysis may occur. Crepitation of the neck secondary tosubcutanous air may be elicited (Figure 513).


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WORKUP FOR LARYNGEAL TRAUMAThe field management of the patient with suspected laryngeal injuryconsists of stabilization of the cervical spine and establishment of anairway. In the event of life-threatening airway compromise, intubation

or tracheostomy in the field may be necessary. After the patient hasbeen stabilized and other potential life-threatening injuries are undercontrol, the physical examination and assessment of the neck maycommence for evaluation for laryngeal trauma. The workup forlaryngeal trauma consists of physical examination of the neck, fiber-optic laryngoscopic examination, radiologic examination, and operativelaryngoscopy. Stridor is the most common sign in patients with upperairway compromise. The type of stridor may be indicative of thelocation of the injury. Combined inspiratory and expiratory stridorsuggests some degree of obstruction at the level of the glottis.Expiratory stridor is more consistent with a lower airway injury. On theother hand, inspiratory stridor is indicative of supraglottic airway

obstruction.5The presence of both stridor and hemoptysis has beenassociated with severe laryngeal trauma, displaced fractures oflaryngeal cartilage, significant endolaryngeal or laryngopharyngealedema or hematoma, or large mucosal tears exposing cartilage.6A thorough physical examination must be performed with specialattention to the presence of neck tenderness, crepitus owing tosubcutaneous emphysema, soft tissue swelling, and loss of thyroidcartilage prominence. Fiber-optic laryngoscopy in the stable patient isan essential element of the physical examination and should focus onvocal cord mobility, tears, mucosal edema, hematoma, and dislocatedor exposed cartilage. If limited range of motion of the vocal cords isnoted, a structural deformity or arytenoid dislocation is likely. On theother hand, immobility of the vocal cords suggests recurrent laryngealnerve injury.5

The patient presenting with soft tissue injury alone will often displayedema, submucosal hemorrhage, and ecchymosis. Laceration of themucosa, exposed cartilage, arytenoid cartilage dislocation, anddisruption of the laryngeal architecture are highly suspicious oflaryngeal framework injury. Despite the above generalizations, somepatients with minimally displaced fractures of the larynx will presentwith a benign appearance of the larynx, and the fracture will be misseduntil the laryngeal edema has subsided, leaving the dislocation orlaryngeal framework abnormality to be manifest as persistent

hoarseness or dysphagia.

RADIOLOGIC EVALUATIONIf cervical spine injury is suspected, it must be evaluated with cervicalfilms prior to movement of the head. Chest radiography should bedone to rule out a pneumothorax. Conventional neck radiographs canbe used to screen for subcutaneous emphysema, whereas, historically,fluoroscopy was used in assessment of vocal function. With the adventof computed tomographic (CT) scanning, this study has supplantedlaryngograms and laryngeal tomography.

The laryngeal CT scan is the most useful radiologic examination forevaluating laryngeal injury. There is some debate regarding the utilityof CT scans in cases at the ends of the disease spectrum. Stringer and


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Schaefer do not recommend CT scan in those individuals with minimalcervical trauma and a normal physical examination as the scan will notchange the management. They also do not recommend CT scans inindividuals who have penetrating injuries, obvious fractures, and large

lacerations and in those who will require open exploration. They donote that there are exceptions for which the CT scan can serve as aroadmap for structural repair.5 Bent et al routinely used CT scans toevaluate severe injuries that required operative management. Theyfound that CT scans assisted in anticipating specific injuries and aidedwith the planning of the operative procedure.7 In the vast majority oflaryngeal trauma cases, CT scans offer better visualization of thesubglotticand anterior commissure areas, can help identify clinicallyunapparent cartilage fractures, and can verify laryngoscopic findings.8Provided that the radiographic facilities are present and the patient isstable, a 2 mm CT scan or a spiral CT scan through the larynx offersthe maximal detail as to the extent of laryngeal framework injury. More

recently, with the use of spiral CT scans and three-dimensionalreconstruction, virtual laryngoscopy and bronchoscopy have becomepossible. Their role in laryngeal fracture diagnosis and managementhas yet to be confirmed.Carotid arteriography may be indicated in penetrating injuries to helpreveal vascular injuries. If esophageal or pharyngeal tears aresuspected, a Gastrografin (meglumine diatrizoate) swallow may beindicated. Gastrografin is the preferred agent over barium owing to thepossibility of a fistula. In these cases, Gastrografin is less irritating tothe soft tissues.

OPERATIVE ENDOSCOPIC EVALUATIONOperative endoscopic examination by direct operative laryngoscopy,esophagoscopy, and bronchoscopy allows the treating surgeon toassess fully the extent of mucosal injury and disruption of the laryngealframework. Direct visualization of laryngeal structures has advantagesover flexible laryngoscopy or radiographic examination in thatpalpation of the structures may be performed. Subglottis and trachealinjuries may be missed by fiberoptic examination; injuries to theseareas are better defined by operative laryngoscopy. Mucosal tears andcartilage exposure that appear as soft issue injuries or edema by CTscan can be mapped without difficulty. Provided that the operativerisks are minimal, the managing physician should have a low threshold

for operative endoscopic evaluation of the patients with suspectedlaryngeal trauma.

EMERGENCY MANAGEMENTIn the initial management of laryngeal trauma, securing and stabilizingthe airway are of paramount importance. However, there iscontroversy regarding the optimal method of establishing a patentairway. Oral intubation in the setting of laryngeal trauma can beprecarious owing to the possibility of further damaging the larynx, thecreation of false passages, and precipitating loss of a tenuous airway.For these reasons, it is recommended that if intubation is necessary, itis to be done after cervical spine injuries have been ruled out and thelaryngeal anatomy has been defined by prior fiber-optic laryngoscopy


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and that it be done in a setting with access to direct visualization withoperative bronchoscopes and with equipment and personnel requiredfor a tracheostomy. A clinician experienced in airway managementshould carry out the procedure of intubation.

Owing to the inherent risks of intubation in the setting of laryngealtrauma, many authors recommend a tracheostomy under localanesthesia.7,9,10 A tracheostomy provides a method of stabilizing theairway with less risk of loss or further injury of the airway.5 Optimally,tracheostomies for laryngeal trauma should be performed at the fourthto fifth ring of the trachea. By performing the tracheostomy lower thanusual, further damage to existing injuries can be avoided. A verticalincision also affords better exposure so that, in the case oflaryngotracheal separation, the trachea may be better accessed if ithas retracted inferiorly.11 Cricothyrotomy should be used only as anemergency method of airway establishment and should be convertedto a standard tracheostomy as soon as possible. The possible sequela

of not recognizing a cricothyrotomy in the setting of laryngeal injuryinclude (a) the subsequent development of perichondritis and necrosisof the cricoid cartilage, (b) the development of subglottic stenosis, and(c) injury to the conus elasticus and the vocal cords. Therefore, anytracheostomy done in the field or in the emergency setting should becarefully evaluated for the possibility that it is a cricothyrotomy or thatit has caused cricoid injury. In the event that a high tracheostomy or acricothyrotomy is present, the airway access should be converted to aconventional tracheostomy below the second tracheal ring. Thepreferred time for revision tracheostomy after cricothyrotomy is within24 hours after the initial operation.

CONSERVATIVE MANAGEMENTAfter the initial evaluation and management of emergent airwayissues, further treatment is divided into nonoperative and operativemanagement. A conservative approach can be taken in patients withminimal soft tissue swelling or small hematomas who are stable andwithout evidence of respiratory compromise. Conservativemanagement should be reserved for soft tissue injuries andnondisplaced laryngeal fractures. Hematoma and edema of the larynxoften resolve spontaneously if there is no evidence of other injury.Conservative management is also appropriate in small mucosallacerations or avulsions that do not involve the free edge of the vocal

cord or anterior commissure. Observation is also appropriate whenthere is a nondisplaced single thyroid cartilage fracture withoutexposed cartilage and mucosal laceration.Endoscopic evaluation of the larynx and trachea should be carried outif there is suspected laryngeal fracture, mucosal laceration, oremphysema of the neck. If there is extensive soft tissue swelling withairway compromise but no evidence of framework injury or mucosallaceration, the surgeon may elect to perform a tracheostomy withoutopen surgical exploration of the larynx. Putting the larynx at rest withconservative treatment will allow the optimum chance for edema tosubside while safeguarding the airway. Conservative managementconsists of observation, bed rest, voice rest, humidification of inspiredair, antacids, and antibiotics. If a tracheostomy is not necessary, the


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patient is observed for 24 hours in an inpatient setting. During the 24hours of observation, the patient should be followed for evidence ofairway compromise from progressive swelling. In an effort to preventfurther swelling and reduce the edema present, bed rest with elevation

of the head is indicated. Similarly, the goal of voice rest is to reduceswelling. Corticosteroids have been used for their anti-inflammatoryproperties and anecdotally prevent the progression of edema.Humidification of inspired air is thought to prevent crust formation ifmucosal damage is present.12 Koufman has suggested that antacid usemay be beneficial by decreasing the incidence of mucosal irritation andpossible laryngeal stenosis from gastroesophageal reflux.13 Antibioticsare indicated, especially in patients with multiple fractures in whomthere is an increased risk of infection and perichondritis. Furthermore,a clear liquid diet may be beneficial initially. A nasogastric tube shouldbe avoided if possible owing to the risk of further injury duringplacement. In addition, with extended placement of a nasogastric tube,

there is risk of mucosal ulceration in the postcricoid region.3

SURGICAL MANAGEMENTInjuries requiring surgical intervention include those with (1) exposedcartilage, (2) large mucosal lacerations, (3) lacerations involving thefree edge of the vocal cord, (4) vocal cord immobility, (5) dislocatedarytenoid cartilages, (6) displaced cartilage fractures, and (7) any neckinjury with airway obstruction. The timing of surgical repair has beendebated in the past, with some authors arguing that delaying surgery 3to 5 days allowed resolution of edema and therefore better recognitionof the anatomy. However, the current consensus is that outcomes areimproved with early intervention. In one study, significantly better

outcomes were noted in the group that was surgically repaired within24 hours when compared with the group that was treated within 2 to 7days.2 A delay of greater than 24 hours to surgical repair has also beenfound to be associated with an increased incidence of woundinfections, especially with supraglottic injuries.14Similar results have been reported in several studies with regard to thevoice. Waiting longer than 48 hours for surgical repair is associatedwith increased laryngeal dysfunction.3 Early intervention may helpreduce uncontrolled healing of lacerations that result in scarformation.7The immediate goals of surgical repair may be guided bythe extent of the deficit and the needs of the patient. Clearly,intervention in a laryngeal fracture may have to be delayed in anunstable patient with multiple trauma. In contrast, the patient with alaryngeal fracture who is a voice professional will want to haveeverything possible done to restore voice function despite a stableairway. The early goals of surgical intervention should be to establish asafe airway, document the injury, repair cartilage injuries and restorethe laryngeal framework, repair soft tissue lacerations, and promoteearly healing of the injury by prevention of infection and tissuenecrosis.In the repair of laryngeal trauma, the long-term goals should beoptimum functional restoration of voice, airway, and swallowing.Although not a common injury, surgical management of laryngeal

fractures has many possible variations. Some of these variations


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depend on the method of fracture reduction, whereas others dependon the method of stabilization and stenting technique used. Anothervariation depends on the site of fracture. Fractures of the thyroid andcricoid cartilages may be repaired by open reduction and rigid fixation,

whereas arytenoid cartilage dislocation and laryngotracheal separationare more often treated by repair followed by endolaryngeal stenting.Table 512 outlines some of the types of injuries to be considered inthe repair of laryngeal trauma.In an effort to optimize the outcomes in laryngeal fractures, uniqueaspects of the laryngeal anatomy and function must be considered.

The following factors are worth detailing: (a) laryngeal cartilageswithout great blood supply are in contact with mucosa; (b) the mucosalsurface is in contact with contaminated upper airway secretions,making infection after injury possible; (c) the larynx is subject to greatmovement during normal deglutition and respiration, makingstabilization difficult; and (d) the relatively small laryngeal cartilages

have a great number of intrinsic and extrinsic muscles attached,making functional outcomes uncertain after laryngeal fracture. Tocounter these unique problems in the repair of laryngeal fractures, thelaryngeal surgeon should (a) strive to reduce the amount of mucosalloss and hasten mucosal healing, (b) improve cartilage survival by rigidfixation and movement reduction, and (c) if necessary, prevent cicatrixformation during healing by the use of endolaryngeal stenting.

The first step in any planned surgical treatment of a laryngeal fractureis a rigid direct laryngoscopy to evaluate the extent of mucosal injuryand to palpate the arytenoid cartilages for dislocation or immobility.Laryngeal exploration is performed through a horizontal incision at thelevel of the cricothyroid membrane. Subplatysmal flaps are elevatedfrom the level of the hyoid bone to the sternal notch. The strapmuscles are separated vertically at the midline raphe and retractedlaterally. The larynx is entered, depending on the site of injury, througha midline thyrotomy or through the thyroid cartilage fracture if thefracture line runs within 2 to 3 mm of the midline of the thyroidcartilage. Care is taken to avoid injury to the anterior commissure. Thiscan be accomplished by horizontally dividing the cricothyroidmembrane prior to performing the midline thyrotomy and directlyviewing the undersurface of the vocal folds from below. If there isdisruption of the anterior commissure tendon, the surgeon mustcarefully search for and reattach it to the thyroid cartilage.

After exposure of the endolarynx, any mucosal lacerations areapproximated with fine absorbable sutures. Fast-absorbing mild 4-0chromic sutures are used. If possible, knots should be placed outsidethe lumen to prevent formation of granulation tissue. In mostinstances, mucosal injuries can be repaired with adjacent mucosa.When mucosal injuries are large, as may be present in an arytenoidcartilage avulsion, a piriform sinus mucosal flap may be used to coverany exposed cartilage. If there is extensive mucosal damage in themembranous portion of the vocal fold, re-establishment of mucosa maybe accomplished by the use of free buccal mucosal or dermal grafts. Acareful examination of the repair should show that all of the exposedcartilage is covered without tension. Pedicled mucosal flaps and

mucosal or dermal grafts are used if there is not enough adjacent


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mucosa within the larynx to cover all exposed cartilage. These freegrafts are of second choice because there is a greater likelihood of scarformation with their use compared with local mucosal flaps. In addition,these free grafts carry the morbidity associated with additional

incisions.5

The importance of restoring the lining of the larynx isattributable to the inherent tendency of exposed cartilage to facilitatethe formation of granulation tissue, subsequently leading to fibrosisand laryngeal stenosis. There is also an increased risk of perichondritiswhen cartilage is left exposed. Care should be exercised to avoidaggressive dbridement of soft tissue or mucosa. Because of theunique nature of the laryngeal framework and the attached mucosa,only devitalized tissue should be removed. Any removed tissue shouldbe replaced by local adjacent tissue transfer or soft tissue grafts. Thisis to prevent late glottal incompetence.Another basic principle of laryngeal trauma surgery is to preserve asmuch cartilage as possible. Even free fragments of cartilage can be

used to provide a scaffolding and stability, provided that they arecovered with viable mucosa. If free cartilage fragments are used, theyshould be fixated with suture or miniplates. Mildly displaced simplefractures can be repaired with nonabsorbable sutures through theouter perichondrium. Displaced fractures of laryngeal cartilage arereduced and immobilized. To prevent chondritis, very small pieces ofcartilage without intact perichondrium are dbrided. Fractures can befixated with wire, nonabsorbable suture, or miniplates. If suture isused, fracture-site sutures should not be tightened until all fracturesare reduced to avoid further damage to the mucosa by tearing. Internalfixation of laryngeal fractures may be performed if there are multiplefractures or fractures with displacement, or it may be used instead ofinternal laryngeal stenting. Titanium miniplates offer the advantage ofsuperior alignment of displaced fractures because of the three-dimensional nature of miniplates (Figure 515).15Reconstruction plates used in facial fracture repair may be used inlaryngeal fracture repair. These plates are bioimplants made oftitanium, stainless steel, or polyglycolic acid. Being malleable, theseplates can be used as an internal scaffold for sutures or screws to fixthe laryngeal fracture fragments into position. The three-dimensionalcontour of the laryngeal skeleton may be re-established with a singlereconstruction plate bent to the shape of the thyroid cartilage. For thecricoid cartilage, it may be used to stabilize comminuted fragments

and provide rigid fixation to the fragments. The screws and plates arebest used in ossified cartilages but may be used with care innonossified cartilage. Because of the soft nature of the cartilage,surgical tapping and drilling of the cartilage are not necessary. Ingeneral, four to six 5.0 mm by 2.0 mm screws serve to fix the laryngealskeleton. Although we have also tried microplates, the smaller screwsand the tendency to strip the smaller holes make the miniplate systemmore useful. In the rare adolescent or pediatric patient in whom thecartilage is thin, sutures alone are used to fixate the fragments ontothe miniplate scaffold, thereby achieving stabilization without the needfor screws.In situations in which rigid internal fixation or immobilization cannot be

achieved, laryngeal stenting will be necessary. Stents are also


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indicated when there is injury to the anterior commissure or whenextensive soft tissue injury is present. If mucosal grafting is required,the internal stent serves to hold the graft in approximation to the rawsurface to be grafted. The goal of stenting is to provide stability and

prevent mucosal adhesions and subsequent laryngeal scarring. Thetype of stent to be used is controversial. Soft stents may be made of afinger cot packed with antibiotic-impregnated cotton gauze. Softsemirigid stents made of Silastic are commercially available in differentsizes, from child to female to male. These can be inserted and modifiedaccording to need. Theoretically, soft stents result in less damage tosurrounding tissue than firmer stents. However, many authors havefound an increased risk of infection and formation of granulation tissuewith soft stents.7,16 Firm stents are usually made of silicone, Silastic,or Portex. They are secured in a similar fashion as soft stents.

The stent is fixed with heavy nonabsorbable suture so that the superiorend is at the aryepiglottic folds and the inferior end is above the

tracheostomy site. The stent should be placed so that it moves withthe larynx during swallowing. It can be secured with two mattresssutures through the skin, then through the thyroid cartilage below thelevel of the glottis, and then through the stent and out the cartilageand skin on the opposite side. The sutures can be fastened to buttonson the skin. Regardless of the method of suturing, the stent should beeasily removed at endoscopy. Furthermore, the stent should be fixed insuch a manner that if a suture breaks, the stent may still berecoverable.5

There has been controversy regarding the optimal time period thatstents should remain in place. The beneficial effects of laryngealstabilization and prevention of scar formation should be weighedagainst the risk of infection and irritation leading to granulation tissueand scar formation with subsequent laryngeal stenosis. Previously,longer periods of time, up to 6 weeks, were favored for stentplacement. Currently, most authors recommend that stents beremoved after about 2 to 3 weeks, providing that fractures have beenstabilized and lacerations closed effectively.2,5 After the stent isremoved at direct laryngoscopy, the need for additional removal ofgranulation tissue can be assessed. If granulation tissue requiresremoval, a carbon dioxide laser can be used.5Despite controversy regarding the management of severe laryngealtrauma involving comminuted fractures and significant endolaryngeal

injury, there is consensus that neither grafts nor stents are substitutesfor meticulous primary closure of mucosal wounds and diligentreduction and internal fixation of fractures. Some specialized injuriesfrom laryngeal trauma may occur as a consequence of closed or openinjuries. These merit individual discussion below.

DISLOCATION OF THE CRICOTHYROIDJOINTUsually with trauma, the inferior aspect of the thyroid cartilage isdisplaced posteriorly. As a result of his displacement, the recurrentlaryngeal nerve may be compromised near the cricothyroid joint,resulting in vocal cord paralysis.Vocal fold paralysis owing tocricothyroid joint avulsion is often temporary, and function usuallyreturns in 3 to 4 weeks. If no recovery of function is noted after 8 to 12


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weeks, spontaneous function is unlikely to return. At this point,decompression of the nerve by resection of the inferior cornu of thethyroid cartilage may be considered since the cause of paralysis inmany cases is neuropraxia. Electromyographic (EMG) studies of the

vocal cord may be useful in assessing the utility of decompression. Ifthe vocal cord is paralyzed longer than 9 months, the long-termprognosis is poor.3

SUPRAGLOTTIC INJURIESSupraglottic injuries require a more aggressive surgical approachowing to the high incidence of infection and fibrosis. In some isolatedsupraglottic injuries, the epiglottis may be avulsed from its anteriorattachments, thereby allowing the epiglottis to prolapse posteriorlyinto the laryngeal lumen. In these instances, the epiglottis may beresected with no alteration in swallowing function. If the trauma ismore extensive, a portion of the thyroid cartilage and false vocal cords

can be resected in addition to the epiglottis as in a standard horizontalsupraglottic laryngectomy.3 Generally, supraglottic injuries result inhorizontal fractures of the superior aspect of the thyroid alae, resultingin avulsion of the epiglottis superiorly and posteriorly. The epiglottis isthen prone to fixation in the posterior position owing to scarring. Inaddition, fixation of the arytenoid cartilages can occur in untreatedinjuries, leading to eventual laryngeal stenosis. One exception to theabove approach is when there is associated vocal cord paralysis orglottic trauma. With vocal fold paralysis or concomitant glottic injuries,supraglottic resection should not be done owing to the increasedincidence of aspiration. Rather, the supraglottic region should bereconstructed and the epiglottis removed.3

GLOTTIC INJURIESWith glottic injuries, fractures of the thyroid cartilage often occur at thelevel of attachment of the true vocal cords. Dislocation of one or botharytenoid cartilages with resultant vocal cord immobility is common(Figure 516). Dislocated arytenoid cartilages are realigned in theircorrect position with relation to the other laryngeal structures. Thesecartilages should not be fixated or removed. As with mucosal tears inother areas, primary reapproximation of the tissue should beattempted. If the mucosa cannot be closed primarily, advancementflaps of mucosa of the piriform sinus area can be used. If vocal cordimmobility is present and is secondary to nerve injury, no corrective

action should be taken since spontaneous return of vocal cord functionis common.

CRICOTRACHEAL SEPARATIONCricotracheal separation is a devastating injury with uniquecharacteristics that require close attention. Unfortunately, most ofthese patients do not survive the acute airway obstruction that occurs.If they do make it to the hospital alive, the airway is often tenuousowing to the loss of cricoid support. There is also a high likelihood ofinjury to the recurrent laryngeal nerves. Once an airway is securedthrough tracheostomy, definitive repair can be planned. These patients

are at high risk of development of subglottic stenosis.


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CRICOID CARTILAGE FRACTUREOften the cricoid cartilage is fractured in two sites laterally, resulting ina telescoping of the cricoid cartilage anteriorly to posteriorly. If this is

the case, the cartilage fractures should be exposed, reduced, andfixated, often requiring a laryngeal stent (Figure 517). Care should betaken to avoid injury to the cricothyroid muscle when repairing cricoidcartilage fractures. When the cricoid cartilage is intact, mucosa shouldbe approximated with absorbable suture. To lessen the tension on thisrepair, sutures can be placed from the upper border of the cricoidcartilage around the first or second tracheal ring.5 In situations in whichthe cricoid cartilage fracture is comminuted, internal fixation must beperformed to offer stabilization during restructuring of the cricoid. Asmuch as one-third of the anterior part of the cricoid cartilage can berepaired using the sternohyoid muscle and its overlying fascia.17 Inpatients with combined compromise of the trachea and the cricoidcartilage, sleeve resection and primary repair may be performed.18

RECURRENT LARYNGEAL NERVE INJURYIf the recurrent laryngeal nerve is severed and this is recognized at thetime of exploration, the best approach is to reanastomose thetransected nerve. Although vocal fold mobility may not be regained,muscle atrophy can be minimized through nerve regeneration, therebyimproving the quality of the voice.5

PENETRATING LARYNGEAL INJURIESThe basic principles of management of blunt laryngeal injuries apply to

penetrating injuries to the larynx. Owing to the especially destructivenature of high-velocity gunshot wounds, these injuries deserve specialcomment.With gunshot wounds, tissue viability is difficult to assessinitially. The high energy that the bullet imparts to the soft tissue leadsto a wider area of significant injury than simply the path of the missile.Furthermore, the course of the bullet is often erratic. Some authorsrecommend delaying definitive surgical repair so that the extent ofnonviable tissue becomes apparent.3,6 Other authors do not suggestdelaying surgical intervention but rather emphasize that a wide areamust be excised because the extent of devitalized tissue is not evidentinitially. 2,9,17 In either situation, all viable structures should beconserved. However, owing to the severe structural disruption of this

type of injury, stenting is often necessary. At times, the injury is somassive that partial or total laryngectomy is indicated. Unlike gunshotwounds, knife injuries do not impart a significant force to soft tissuedistant from the course of the penetrating object. Therefore, the risk ofnonviable soft tissue distant from the penetrating course of the knife isnot present.

PEDIATRIC LARYNGEAL TRAUMAThe same basic management principles discussed for the adultpopulation also apply to the pediatric population, with a few additionalcaveats regarding securing a childs airway. Owing to the rapid oxygen

desaturation of a child compared with an adult, efficiency in obtaining


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and stabilizing the airway is paramount. Furthermore, tracheostomywith local anesthesia is not a reasonable option in a scared, injuredchild. The airway should be stabilized under direct visualization withbronchoscopy; if needed, tracheostomy may then be performed over

the bronchoscope. During endoscopy following the tracheostomy, thelaryngeal injuries can be assessed.

COMPLICATIONSEven with the prompt recognition of laryngeal injuries and appropriatemanagement, complications including granulation tissue, laryngealstenosis, vocal cord paralysis, and aspiration are possible. Untreateddisplaced fractures may heal with dystrophic chondrification (Figure518). Chondronecrosis with prolonged granulation tissue andprogressive cicatrix formation is a feared complication of laryngealfracture. Factors that increase the formation of granulation tissueinclude the presence of cartilage without mucosal covering and the

presence of a stent. Granulation tissue increases the risk of fibrosis,which subsequently leads to stenosis. The primary closure oflacerations and the careful covering of all exposed cartilage withmucosa are of paramount importance. Other techniques have beenattempted to reduce the formation of granulation tissue. Thesemethods include intralesional and systemic corticosteroids, splinting,and irradiation.However, none of these treatment options have proven to bebeneficial. Therefore, the optimal methods of preventing granulationtissue are the initial complete mucosal closure over cartilaginousstructures and maintaining a stent in place the shortest period of timerequired for fixation. Laryngeal stenosis may develop despitemeticulous care after injury. In the case of supraglottic stenosis, thescar tissue may be excised with the carbon dioxide laser. If needed forwound coverage, local mucosal flaps or buccal mucosal grafts can beused. Similarly with glottic stenosis, posterior or interarytenoid scarringcan be excised and local advancement flaps used if necessary. In thecase of thin webs, a laser may be used to divide the web. If the glotticstenosis is severe, a laryngofissure with direct excision of the stenoticarea is likely necessary. In these severe cases, a stent with a tissuegraft is often placed to facilitate re-epithelialization.12 In late or repeatreconstructions of the larynx in which laryngeal stenosis is an ongoingissue, the use of a conforming laryngeal prosthesis is invaluable. This

application is described by Montgomery and Montgomery.19Laryngeal stenosis in the subglottic area is more difficult to treateffectively. With limited subglottic stenosis, excision of fibrotic tissuewith a carbon dioxide laser and repeated dilations of the stenotic areamay be adequate. In cases of more severe subglottic stenosis, cricoidsplits with cartilage grafting are required. To stabilize the restructuringpostoperatively, a stent is often needed. Tracheal stenosis of up to 4cm can be resected with subsequent end-to-end trachealanastomosis.12 Late reconstructions of the larynx using pedicled andautogenous grafts have been used with good results in adults sufferingfrom laryngeal stenosis after laryngeal trauma.2023In addition to laryngeal stenosis, another possible complication isparalysis of the vocal cords. The cause of an immobile vocal cord must


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be determined to make appropriate management decisions. Toevaluate whether an injured recurrent laryngeal nerve or acricoarytenoid joint fixation is responsible for vocal fold dysfunction,direct laryngoscopy is performed. During the laryngoscopy, the

arytenoid cartilage is palpated to evaluate mobility. If the arytenoidcartilage is mobile, injury of the

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