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Skandalakis' Surgical Anatomy > Chapter 13. Pharynx >

History

The anatomic and surgical history of the pharynx is shown in Table 13-1.

Table 13-1. Anatomic and Surgical History of the Pharynx


Morgagni 1717 Described the pharyngeal sinus of Morgagni, a space in the nasopharynx between the upper border of the superior constrictor muscle and the base of the skull
Rosenmüller 1808 Described the lateral pharyngeal recess (fossa of Rosenmüller)
Zukerkandl 1882 Described the pharyngeal tonsil
Mikulicz 1886 Reconstructed esophageal and pharyngeal stomas with inverted skin flaps
Beck 1905 Used reversed gastric tube
Jianu 1912
Gavriliu & Georgescu 1951
Roux 1907 Used jejunum as pedicle graft
Herzen 1908
Vulliet 1911 Used transverse colon for reconstruction
Kelling 1911
Trotter 1913 Reconstructed the posterior and anterior hypopharyngeal wall with horizontal skin flaps
Kirschner 1920 Pioneered gastric transplantation, bringing the stomach to the neck
Wookey 1942 Developed a two-staged repair: doubled a long, full-thickness cervical pedicle flap and sutured it to the pharynx and esophagus, closing the raw surface; repaired the fistula later by undercutting and suturing the skin margins
Hynes 1950 Performed pharyngoplasty by muscle transplantation, producing a sphincterlike mechanism
Goligher & Robin 1954 Used left colon for reconstruction via presternal route
Asherson 1954 Performed partial excision of the posterior wall of the pharynx for carcinoma and used the proximal laryngotracheal tube for reconstruction
Seidenberg et al. 1959 Developed microvascular technique using jejunum and anastomosing the mesenteric vessels to the superior thyroid artery and anterior facial vein
Ong & Lee 1960 Performed pharyngogastric anastomosis after esophagopharyngectomy for correction of the laryngopharynx and cervical esophagus
Iskeceli 1962 Experimented with jejunal transplant to the pharynx in experimental animals
Bakamjian 1965 Used deltopectoral flap for pharyngoesophageal reconstruction
Ogura & Dedo 1965 Used thoracoacromial flap to repair a pharyngostoma
Yamagishi et al. 1970 Replaced esophagus up to the pharynx with a totally detached isoperistaltic gastric tube
Ariyan 1979 Used pectoralis major muscle flap for pharyngoesophageal reconstruction
McLear et al. 1991 Used jejunal free flap for reconstruction of hypopharyngeal stricture
Anthony et al. 1994 Performed pharyngoesophageal reconstruction with radial forearm free flap
Wax et al. 1996 Reconstructed the oropharynx with lateral arm free flap

History table compiled by David A. McClusky III and John E. Skandalakis.

References

Missotten FEM. Historical review of pharyngo-oesophageal reconstruction after resection for carcinoma of pharynx and cervical oesophagus. Clin Otolaryngol 1983;8:345-362.

Pigott RW. The results of pharyngoplasty by muscle transplantation by Wilfred Hynes. Br J Plast Surg 1993;46:440-442.

Schmidt JE. Medical Discoveries: Who and When. Springfield, IL: Charles C. Thomas, 1959.

Embryogenesis

Normal Development

To understand the anatomy of the pharynx and its associated arteries and nerves and to avoid possible complications related to surgical treatment of congenital lesions in this relatively inaccessible area, a thorough knowledge of the basic embryologic development of the pharynx is imperative. The pharynx is a product of differentiation of the embryonic foregut. It occupies a major portion of the foregut in the first few weeks of embryonic development and precedes the appearance of the more caudal regions. The cranial portion of the foregut transforms from a flat tube into a complicated collection of structures between the fourth and sixth weeks of embryogenesis.

Structures derived from the pharynx can be divided into the lateral branchial apparatus and the unpaired ventral endodermal floor. [Note from the authors: The term "branchial" is used in many chapters of this book. Nomina Anatomica, 6th edition, page E28, lists "branchial" as its second choice, and "pharyngeal" as its first choice. Many current authors strongly prefer "pharyngeal" unless one is referring to lower vertebrates with gills, etc.]

The branchial apparatus contains paired endodermal pharyngeal pouches with ectodermal clefts. Mesodermal arches occur between the consecutive pairs. The ventral structure gives rise to the tongue, thyroid, larynx, and trachea.

Externally, the branchial apparatus is marked by four ectodermal branchial clefts on each side of the pharynx of the embryo. On the inner surface, the pharynx, which arises from the stomodeal plate, evaginates into five pouches. The first four of these correspond to the external branchial clefts. Mesodermal arches (Fig. 13-1) are found between the corresponding cleft-pouch sets. Each arch contains a skeletal element, an artery, and the primordia of nerves and muscles. The derivatives of the branchial arches are listed in Table 13-2. (Readers will notice that Table 13-2 indicates the existence of 6 arches. However, for all practical purposes, there are only 4, because the fifth disappears early, and the sixth unites with the fourth.)

Table 13-2. Summary of Adult Structures Derived from Pharyngeal Arches


Arch Derivatives
Pharyngeal Arch Muscles Skeletal Structures Ligaments Pouch Derivatives Groove Derivatives Nerve Supply
First (mandibular) Mastication muscles (Meckel's cartilage) Anterior ligament of malleus Tubotympanic recess (tympanic membrane, tympanic cavity, mastoid antrum, auditory tube) External auditory canal V (trigeminal)
Mylohyoid Malleus Sphenomandibular ligament      
Anterior belly of digastric Incus        
Tensor tympani Ventral end of mandible        
Tensor veli palatini          
Second (hyoid) Facial expression muscles (Reichert's cartilage) Stylohyoid ligament Tonsillar fossa None VII (facial)
Stapedius Stapes      
Stylohyoid Styloid process        
Posterior belly of digastric Hyoid bone (lesser horn and upper body)        
Third Stylopharyngeus Hyoid bone (greater horn and lower body) None Inferior parathyroid None IX (glossopharyngeal)
    Thymus    
Fourth and sixth combined Cricothyroid Laryngeal cartilages (cricoid, thyroid, arytenoid, corniculate, cuneiform) None Superior parathyroids None X (vagus)
Levator veli palatini   Ultimobranchial bodies    
Constrictors of pharynx      
Intrinsic muscles of larynx          

Source: Johnson KE, Slaby FJ, Bohn RC. Anatomy: Review for USMLE, Step 1, 2nd Ed. Alexandria, Va.: J & S Publishing, 1998, p. 83; with permission.

In the adult pharynx, the eustachian tube and the tonsillar fossa represent derivatives of the first and second branchial pouches respectively. The third pouch is near the entry of the piriform recess, and the fourth is near the apex. Laryngeal ventricles may be related to the fifth and sixth pouches.

Congenital Anomalies of the Pharynx

Anomalies of the Lateral Branchial Apparatus

Epithelium-lined cysts, sinuses, and fistulas may occur as a result of malfunction in the normal differentiation process of the branchial apparatus. Understanding the anomalies of the branchial apparatus helps the surgeon predict the location and course of these lesions and surrounding important normal structures, and thus to avoid their injury at surgery.

First Cleft and Pouch Defects

The fistulas, sinuses, and cysts of the first branchial cleft are intimately related to the external auditory canal and the facial nerve; they are presented in the chapter on the neck. First pouch defects are rare, but may present as nasopharyngeal cysts (Fig. 13-2). The opening of the sinuses can be near the eustachian cushion.

Second Cleft and Pouch Defects

Second cleft and pouch defects may involve the pharynx. Therefore these lesions and their courses are pertinent to understanding the pharynx.

Complete Fistulas

Almost all complete branchial fistulas are derived from the ventral portion of the second cleft and pouch. The external opening is in the lower third of the neck, anterior to the sternocleidomastoid muscle. The fistula passes through the deep fascia to reach the carotid sheath. Above the hyoid, the tract turns medially. It passes over and in front of the hypoglossal nerve and between the carotid bifurcation. It enters the pharynx on the anterior face of the superior half of the posterior tonsillar pillar. Alternatively, the opening can be into the tonsil itself. Figure 13-3 depicts the course of the fistula of the second branchial cleft and pouch.

Sinuses Opening into the Pharynx

Sinuses opening into the pharynx are rarely seen. They usually open into the upper half of the posterior tonsillar pillar or into the tonsil itself.

Cysts

The cysts of the second pouch may present clinically as a bulging in the posterior tonsillar pillar. Most are encountered in the neck and may extend between external and internal carotid arteries (Fig. 13-4).

Third Cleft and Pouch Defects

A complete fistula of the third cleft and pouch has never been reported. Such a fistula, theoretically, would pass below the eleventh cranial nerve, over the superior laryngeal nerve and hypoglossal nerve, and posteromedial to the internal carotid artery. It would then open into the pharynx in the upper part of the piriform recess (Fig. 13-3).

Internal sinus tracts derived from the third pouch have been reported. They originated from the apex of the left piriform recess in all cases.

Fourth Cleft and Pouch Defects

A complete fistula of the fourth cleft and pouch has not been reported. Theoretically, the route of this fistula (Fig. 13-5) would be from the apex of the piriform recess, through the cricothyroid membrane (inferior to the cricothyroid muscle), descending into the tracheoesophageal groove and looping around the artery of the fourth arch, passing cephalodorsal to the carotid, looping over the hypoglossal nerve, descending in the neck, passing through the strap muscles and platysma, and exiting low in the neck, anterior to the sternocleidomastoid muscle.

Surgical Considerations

A thorough understanding of the embryology of the branchial structures is essential for the head and neck surgeon. To aid in the complete surgical excision of these structures and to avoid complications, it is important to understand their normal course.

First branchial cleft anomalies may come in close proximity to the facial nerve. Therefore, facial nerve identification and dissection is essential to avoid facial paralysis.

Second branchial cleft anomalies, which are the most common, start in the mid-neck (anterior to the sternocleidomastoid muscle) and course up to the tonsillar fossa. It is important to remove the entire tract up to the tonsil.

Third branchial cleft anomalies start lower in the neck and pass posteromedial to the internal carotid artery and travel caudally to end in the piriform recess.

Fourth branchial cleft anomalies are extremely rare and may present as recurrent thyroiditis. There are no clinical reports of tracts that follow the entire theoretical course (see section above). Instead most start in the piriform apex, usually the left side, and end after only a short distance in the paratracheal region.

Direct laryngoscopy is useful for finding the opening of the tract in the apex of the piriform recess (Fig. 13-6). Cannulation of the tract with a Fogarty catheter is helpful for localization of the tract during neck dissection in the left paratracheal region. Identification of the recurrent laryngeal nerve is important to avoid nerve injury, but may be difficult with previous infection.

Ventral Defects

The embryogenesis and abnormalities of development of the thyroid, parathyroids, and thymus are beyond the scope of this chapter. Information about the thyroid and parathyroids is included in the chapter on the neck; the thymus is considered in the chapter on the mediastinum. However, the anomalies of the descent of the medial anlage, the thyroid, are important in the discussion of the pharynx as it pertains to the lingual thyroid because the entire thyroid may locate in the oropharynx and cause an obstruction of the airway.

Lingual thyroid refers to the failure of the thyroid to descend to its normal location. This gland may be within the tongue, at the normal location of the foramen cecum (Figs. 13-7A, B). It is usually the only thyroid tissue present in the patient. Inadvertent excision of the gland may result in permanent hypothyroidism. Hormonal suppression is usually effective in decreasing the size of the lingual thyroid. Surgery may be selectively used in cases of airway obstruction or swallowing difficulties refractory to hormonal suppression.

Surgical Considerations

During the normal descent of the thyroid gland portions of the tract may remain (may fail to obliterate). These remnants are known as thyroglossal duct cysts. The tract starts in the midline neck and extends to the foramen cecum. It is essential to excise the complete tract and incorporate the central body of the hyoid bone. This is known as a Sistrunk procedure. Failure to excise the central body of the hyoid bone and follow the tract up the foramen cecum increases the recurrence rate.

Regions of the Nasopharynx

The nasopharynx, oropharynx, and laryngopharynx together form the common aerodigestive tract known as the pharynx (Fig. 13-8). These three separate regions are, from the surgeon's perspective, quite different and individually complex. Each region is unique with respect to the lesions that arise there, and each has specific structural and functional considerations. The following pages discuss these three structures.

Development of Nasopharynx

The nasopharynx is full of developmental and morphologic complexity. It contains:

 

Pouch of Luschka (pharyngeal bursa) (Fig. 13-9)

Fossa (pharyngeal recess) of Rosenmuller (Fig. 13-8)

Waldeyer's tonsillar ring (Fig. 13-10)

Eustachian (tubal) tonsil (Fig. 13-10)

Luschka's "gland" (the pharyngeal or third tonsil) (Fig. 13-10)

Eustachian cushion (torus tubarius) (Fig. 13-8)

Pharyngeal (extrasellar) hypophysis (Fig. 13-8)



Developmental considerations (Fig. 13-11) include:

 

Rostral tip of the notochord

Hypophysial pouch (Rathke's pouch)

Craniopharyngeal canal

Presphenoid-basisphenoid synchondrosis

Spheno-occipital synchondrosis

Tubotympanic recess

Pneumatization of the superadjacent sphenoid sinus (age 7-8)

Development of the first two pharyngeal pouches on each side


The nasopharynx may also include the adenoids, Rathke's cleft cysts, chordomas, or craniopharyngioma.

Nomina Anatomica refers to the nasopharynx as the pars nasalis pharyngis, the nasal part of the pharynx. Although the nasopharynx is a part of the pharynx, remember that it is a purely respiratory passage. Under normal circumstances, it is not a part of the digestive tract, as is the pharynx.

The pharynx arises as the expanded cephalic end of the embryonic foregut (Fig. 13-12). The nasal cavities develop separately from the foregut, arising from the nasal pits which deepen into nasal sacs. Since the early 1900s, controversies have existed as to whether the nasopharynx should be considered strictly a part of the nasal cavity, or if it should be regarded as part of the pharynx. From embryogenesis, it is known that some of the original cavity is taken up into the lower part of the nasal cavities. A portion of the original pharyngeal cavity comes to lie above the level of the definitive palate. It is this portion of the pharynx that contributes to at least a portion of the nasopharynx and unites with the deepest part of the nasal sacs.

The caudal extent of the nasopharynx is above the plane of the soft palate (Fig. 13-8) at the level of the opening of the eustachian tube (derived from the first pharyngeal pouch). Therefore, the nasopharynx is derived from the embryonic pharynx below the level of the eustachian tube orifice.

Rostral to the eustachian tube orifice, the nasopharynx develops from the deep extension of the nasal cavities. The preceding conclusions are based on the histology and innervation of the two components of the nasopharynx. The nasal (anterior) nasopharynx possesses the highly vascular respiratory mucosa that is rich in lymphatics and resembles the nasal cavity. Transition occurs at the level of the eustachian tube, where the posterior nasopharynx has stratified squamous epithelium resembling that of the oropharynx.

Congenital Anomalies of the Nasopharynx

Anomalous nasopharyngeal development may be associated with abnormalities of the posterior nasal apertures, including choanal atresia, unilateral or bilateral (Fig. 13-13), and malformation of the posterior aspect of the skull base. Gross abnormalities such as iniencephaly or anencephaly can also be associated with nasopharyngeal wall malformations.

Surgical Anatomy

Surface Anatomy of the Nasopharynx

The nasopharynx extends from the choanae (posterior nasal apertures) (Fig. 13-14) and slopes upward and backward. Its shape follows the slope of medial and lateral boundaries formed by the posterior edges of the vomer and the medial pterygoid plates, respectively (Figs. 13-14, 13-15).



The anterior plane of the soft palate (Fig. 13-8) produces the lower extent of the nasopharynx. This plane intersects the anterior arch of the atlas in its posterior extent. This is the narrowest part of the nasopharynx. It is called the isthmus, and it leads to the oropharynx below.

The nasopharynx is just inferior to the sphenoid bone (Fig. 13-15) and the posterior part of the sphenoid sinus. The hypophysial fossa (Fig. 13-15) and pituitary gland are more cephalad to the sphenoid. The basilar portion of the occipital bone (Fig. 13-15) slopes downward, forming the anterior margin of the foramen magnum (Figs. 13-14, 13-15), which is located posterosuperiorly to the nasopharynx.

Anterosuperiorly, the vomer articulates with the undersurface of the sphenoid bone (Fig. 13-15). Posterior to this articulation lies the pharyngeal sphenoidal fossa. In this fossa lies the pharyngeal hypophysis (Fig. 13-8). Posterior to it, in the same tissue plane, one finds a collection of lymphoid tissue known as the pharyngeal tonsil (Fig. 13-8).

Move inferiorly on the posterior wall of the nasopharynx to find the isthmus. Located below the basiocciput (Fig. 13-14) is the anterior arch of the atlas (Fig. 13-8), and immediately behind it, the dens.

Numerous ligaments are located in this region. The anterior longitudinal ligament is the ligamentous structure most closely related to the posterior wall of the nasopharynx.

The side walls of the nasopharynx are also extremely important. The most prominent structure is the opening of the auditory (eustachian) tube (Fig. 13-14). This is located just behind the inferior nasal turbinate (concha) (Fig. 13-15). The overhang above and behind the orifice is known as the torus tubarius (Figs. 13-8, 13-16). This is formed by the bulge of the fibrocartilage of the auditory tube itself. Gerlach's tonsil (eustatchian or tubal tonsil) (Figs. 13-8, 13-10) is a collection of lymphoid tissue located in the mucous membrane over the pharyngeal orifice of the eustachian tube. The fossa of Rosenmuller (pharyngeal recess) (Fig. 13-8, Fig. 13-17) is located behind the tubal orifice. This is a fairly deep and laterally directed structure. The superior pharyngeal constrictor (Fig. 13-18) lies in the side wall of the nasopharynx. Dense pharyngobasilar fascia, which is attached to the skull base above and to the pterygoid plate laterally (Fig. 13-14), is located on the inner aspect of the superior constrictor. The gap in the fascia allows the eustachian tube to pass. On the outer aspect of the superior constrictor muscle is the weaker buccopharyngeal fascia. It provides a flimsy covering for the wall of the nasopharynx.



An important feature of the nasopharynx is the development of the first two pharyngeal pouches on either side of this cavity (Fig. 13-8, Fig. 13-9). This relationship is important with respect to the development of Waldeyer's ring (Figs. 13-10A & 13-10B). This is an incomplete ring of lymphoid tissue composed of the pharyngeal tonsil, eustachian tonsil, palatine tonsil, and lingual tonsil.

Lying close to the nasopharynx are two noteworthy embryologic structures: the rostral segment of the notochord and the craniopharyngeal canal (Fig. 13-11). Tumors (chordoma and craniopharyngioma, respectively) may arise from these. Both may involve the nasopharynx.

Examination of the Nasopharynx

When the nasopharynx is examined indirectly with a mirror or endoscopically, several significant features become apparent. The perichoana with the posterior tips of the inferior, middle, and superior turbinates (conchae) (Figs. 13-8, 13-16) are readily seen. The posterior vomer sharply divides the posterior choanae (Fig. 13-14). Enlargement of the turbinates (conchae), adenoids, or polyps, or a mucopurulent nasal discharge can be readily apparent in this region. Adenoids usually begin to atrophy after thirteen years of age, and if present in an adult, neoplasia should be considered. Enlarged adenoids in an adult may also raise suspicion for lymphoepithelial hyperplasia associated with an HIV infection. On the exam, juvenile nasopharyngeal angiofibromas can be seen as smooth pulsatile masses, which should never be biopsied because the vascularity of the tumor and the brisk bleeding that accompanies biopsy creates the potential for severe hemorrhage.

Several important landmarks in addition to the torus tubarius (Fig. 13-16) can be seen when the nasopharynx is examined during nasopharyngoscopy. The salpingopharyngeus muscle (Fig. 13-17) is seen to sweep posteriorly and inferiorly from the posterior part of the torus, forming a raised mucosal fold (Fig. 13-16). The pharyngeal recess previously mentioned is actually formed between the pharyngeal wall and the elevation produced by this fold. Gerlach's tonsil underlies this fold. Slight elevation of mucosa in the center of the eustachian tube opening is produced by the underlying levator veli palatini muscle (Figs. 13-8, 13-17). Looking at the roof of the nasopharynx, depression in the midline is frequently seen. This concavity is known as the pharyngeal bursa (Fig. 13-8). The mucosa of this bursa is infiltrated by lymphatic nodules at its periphery, which if sufficiently hyperplastic, forms the adenoids. A persistent remnant of the embryonic notochord in this area may occasionally be seen as a cystic midline nasopharyngeal mass. This is known as the Thornwaldt's cyst and is usually seen later in life.

Residual epithelial elements of Rathke's pouch (Fig. 13-11), an evagination of the stomodeal roof that contributes to the anterior pituitary gland, can give rise to a craniopharyngioma. These usually occur just superior to the pharyngeal bursa in the midline of the nasopharynx, and may also be present as nasopharyngeal masses (Fig. 13-9).

Surgical Considerations

Nasopharyngoscopy, whether with direct flexible or rigid telescopes, allows visualization of the structures and landmarks described above. An indirect mirror exam will also allow excellent visualization of the nasopharynx. However, the latter is limited by the experience of the examiner, the inverted nature of the mirror image, and the cooperation of the patient if the exam is done outside the operating room.

The best way to examine the nasopharynx in detail is under general anesthesia with the patient in a supine position. The soft palate (Figs. 13-8, 13-16) can be retracted by passing catheters through the nares into the oral cavity and out through the mouth. The ends of such catheters are clamped and a mirror is used by the examiner located at the head of the patient to survey the nasopharynx, denote the structural features, and to perform a variety of procedures. These procedures include adenoidectomy, biopsies of any areas suspicious for malignancy, removal or marsupialization of polyps and cysts, cannulation of eustachian tubes, and surgery for nasopharyngeal stenosis (Fig. 13-19). A thorough examination of the three dimensional structure of the nasopharynx under general anesthesia is essential in planning a surgical repair, such as with laterally-based pharyngeal flaps.

Nasopharyngeal examination under general anesthesia is also useful for choanal atresia surgery, although in these cases the catheters cannot always be passed through the nose; different maneuvers to retract the palate may be necessary.

With respect to malignancies confined to the nasopharynx, it is imperative that a complete nasopharyngeal exam is performed and that the examiner is fully aware of the normal anatomy and variations of the nasopharynx. In the case of patients who present with neck masses suggestive of malignancy, a nasopharyngeal exam must always be a part of their head and neck examination. It is also extremely important to examine the nasopharynx of the patients who present with nasal obstruction, epistaxis, or serous otitis media. All of these may result from benign or malignant processes in this region. For example, angiofibromas may cause intermittent epistaxis as well as nasal obstruction. A process near the eustachian tube orifice, such as nasopharyngeal carcinoma or lymphoma, may have unilateral serous otitis media as its only symptom.

Important Anatomic Relationships

Nasopharyngeal walls are composed of four layers from inside to outside:

 

Mucosa

Submucosa or fibrous layer (pharyngobasilar fascia)

Muscular layer

Buccopharyngeal fascia covering the constrictor muscles

The mucous membrane containing ciliated respiratory and nonciliated columnar epithelium is the inner lining. Submucosal connective tissue made of pharyngobasilar fascia is well defined in its attachment to the skull base (Fig. 13-18). External to the superior constrictor muscle is the buccopharyngeal fascia (Fig. 13-16). Attachment of the nasopharynx to the skull base is extremely important. Significant relationships to the middle cranial fossa, to the dehiscence between the petrous temporal bone and foramen lacerum (Fig. 13-14), and to the carotid canal are apparent (Fig. 13-14).

The nasopharynx is attached in the midline to the pharyngeal tubercle on the basal surface on the body of the occipital bone (Fig. 13-18). This attachment extends bilaterally to the petrous temporal bone (Fig. 13-15), and turning forward, continues to the posterior margin of the medial pterygoid plate (Fig. 13-14) and the pterygoid hamulus (Fig. 13-15). The fossa of Rosenmuller (Figs. 13-8, 13-17) lies in the roof of the nasopharynx. Because the internal carotid artery (Fig. 13-20) passes through the foramen lacerum it is close to the nasopharyngeal wall. Expanding masses in the nasopharynx, therefore, can involve and jeopardize the carotid.


The roof of the nasopharynx is the floor of the middle cranial fossa. The sphenoidal sinus (Fig. 13-21), sella turcica, and cavernous sinus in the parasellar region are in close proximity to each other. The middle cranial fossa can be invaded by the tumors of the nasopharynx. Natural routes are via the foramen ovale. Direct extension into the middle cranial fossa can also occur from the roof of the nasopharynx via the foramen lacerum (Fig. 13-14). Growth patterns of nasopharyngeal tumors are not well defined. However, some theories have been proposed based on surgical anatomy of the specimens. Tumors can spread into the orbit, pterygopalatine fossa, infratemporal fossa, and sphenoid sinus or penetrate intracranially. They can thus cause blindness or destruction of the pituitary, as well as extension into the anterior cranial fossa.


Nasopharyngeal lesions may also involve the retropharyngeal or parapharyngeal spaces (Figs. 13-22, 13-23). This can occur since the buccopharyngeal fascia covering the external surface of the nasopharynx is connected to the prevertebral fascia of the deep layer of the deep cervical fascia. This creates a space between the two fascial layers, known as the retropharyngeal space. Another space located laterally occurs between the buccopharyngeal fascia and the fascia of the pterygoid muscles. Near the nasopharynx, that space is called the parapharyngeal space. Tumors or infections can invade this space readily.



Important structures that pass between the skull base and the superior constrictor muscles can usually be seen on anatomic specimens. Removing the mucosa from the medial aspect will reveal the tensor veli palatini (Fig. 13-17) and levator veli palatini muscles, ascending palatine artery, and ascending pharyngeal artery (Fig. 13-24). The salpingopharyngeus muscle (Fig. 13-17) can also be revealed.


The main muscles of the nasopharynx are the tensor and levator veli palatini muscles (Fig. 13-17). These are located in the space between the skull base and the superior constrictor muscle, which will be described under "Myofascial Framework." This space is sealed by the pharyngobasilar fascia (Fig. 13-18). These muscles originate from the pterygoid fossa between the lateral and medial pterygoid plates (Fig. 13-14). They insert into the soft palate (Figs. 13-8, 13-16).

The head and neck surgeon must be familiar with several important considerations. The anterior soft palate is tensed by the action of the tensor veli palatini muscle. This muscle is thought to have an important role in eustachian tube opening and thereby in pressure equalization between the middle ear and the nasopharynx. Other authors implicate the levator veli palatini in this function.

The levator veli palatini crosses the superior border of the superior constrictor muscle and enters the nasopharyngeal mucosa and the lateral border of the soft palate. Contraction of the levator veli palatini muscles elevates the soft palate and seals the oral cavity from the oropharynx. This principle is important when treating patients with velopharyngeal insufficiency and its associated deglutition and speech problems.

Two arteries travel the space below the skull base. These are the ascending pharyngeal, arising from the bifurcation of the internal and external carotid arteries, and the ascending palatine artery, a branch of the facial artery (Fig. 13-24). These vessels are the main contributors of blood supply to the nasopharynx.

Although the anatomy of the skull base is beyond the scope of this chapter, familiarity with the location of two structures is important. The foramen spinosum (Fig. 13-14) is a conduit for the middle meningeal artery (Fig. 13-20). The foramen ovale (Fig. 13-14) provides passage to the mandibular branch of the trigeminal nerve (Fig. 13-21). These foramina may allow spread of malignancies with origins in the intracranial nasopharynx.

The nasopharynx is relatively insensitive, with the main sensory innervation provided by the branches of maxillary division of the trigeminal nerve (Fig. 13-25): the greater and lesser palatine nerves. Cranial nerve IX, the glossopharyngeal nerve (Fig. 13-24), supplies sensory innervation to the mucosal wall as far superiorly as the eustachian tube. Procedures on the nasopharynx, such as mucosal biopsies and adenoidectomies, however, are relatively painless and postoperative requirements for analgesics are minimal.

Surgical Considerations

A very important point in a nasopharyngeal surgical procedure, such as adenoidectomy, is the proximity of the atlanto-axial joint (Fig. 13-8). Muscle spasm or infection after surgery may result in atlanto-axial dislocation, known as Grisel's syndrome. Patients with trisomy 21 (Down syndrome) are at higher risk for this unusual complication.

A variety of benign and malignant neoplasms may occur in the nasopharynx (Tables 13-3 and 13-4). Congenital lesions such as chordomas and craniopharyngiomas may also be present. Malignancies of the salivary glands as well as melanomas and esthesioneuroblastomas (olfactory neuroblastomas) may also be found in the nasopharynx.

Table 13-3. Benign Non-Epithelial Tumors, Involving the Nasal Cavity, Paranasal Sinuses, and Nasopharynx – 156 Cases


Vascular tumors   81
Capillary hemangioma 30  
Cavernous hemangioma 5  
Venous hemangioma 3  
Benign hemangioendothelioma 3  
Angiomatosis 1  
Glomus tumor 1  
Angiofibroma 38  
Osseous and fibro-osseous tumors   52
Osteoma 31  
Fibrous dysplasia 9  
Ossifying fibroma 7  
Osteoblastoma 1  
Giant cell tumor 4  
Chondroma   7
Myxoma   7
Fibroma   5
Leiomyoma   2
Lipoma   1
Rhabdomyoma   1

Source: Fu YS, Perzin KH. Non-epithelial tumors of the nasal cavity, paranasal sinuses, and nasopharynx: a clinicopathologic study. I. General features and vascular tumors. Cancer 33:1275-1288, 1974; with permission.

Table 13-4. Malignant Tumors of Nasopharynx from the Mayo Tissue Registry, 1972 to 1981


Tumor Type Number (%)
Squamous cell carcinoma* 120 (71)
Lymphoma 31 (18)
Miscellaneous 18 (11)
Adenocarcinoma 6  
Plasma cell myeloma 3  
Cylindroma 2  
Rhabdomyosarcoma 2  
Melanoma 2  
Fibrosarcoma 1  
Carcinosarcoma 1  
Unclassified, spindling malignant 1  
neoplasm    
Total 169 (100)

*Combined World Health Organization types 1, 2, and 3.

Source: Neel HB III. Benign and malignant neoplasms of the nasopharynx. In: Cummings CW. Otolaryngology–Head and Neck Surgery (2nd ed). St. Louis: Mosby, 1993; with permission.

Nasopharyngeal carcinoma deserves special attention. The complaints of patients with nasopharyngeal carcinomas are related to the location of the primary tumor and the degree of spread. This is also reflected in the staging of these lesions (Table 13-5). Hearing loss and neck masses are the most common complaints. A tumor in the lateral nasopharynx near or directly involving the mucosa of the eustachian tube orifice leads to tubal compromise. Symptoms of ear blockage, serous otitis media and hearing loss can be present. The nasopharynx is richly supplied by lymphatics. These communicate across the midline and allow for the bilateral metastases to the lymph nodes of the neck by way of the retropharyngeal lymph nodes. High cervical nodes in the posterior triangle (Fig. 13-26) are often affected first.

Table 13-5. Current Pharynx Cancer Staging


Pharynx (including base of tongue, soft palate, and uvula) 
Primary tumor (T)   
Tx Primary tumor cannot be assessed
T0 
 
No evidence of primary tumor
Tis 
 
Carcinoma in situ 
Oropharynx   
T1 
 
Tumor 2 cm or less in greatest dimension
T2 
 
Tumor more than 2 cm but not more than 4 cm in greatest dimension
T3 
 
Tumor more than 4 cm in greatest dimension
T4 
 
Tumor invades adjacent structures, e.g., through cortical bone, soft tissue of neck, deep (extrinsic) muscle of tongue
Nasopharynx   
T1 
 
Tumor limited to one subsite of nasopharynx
T2 
 
Tumor invades more than one subsite of nasopharynx
T3 
 
Tumor invades nasal cavity or oropharynx
T4 
 
Tumor invades skull or cranial nerve(s)
Hypopharynx   
T1 
 
Tumor limited to one subsite of hypopharynx
T2 
 
Tumor invades more than one subsite of hypopharynx or an adjacent site, without fixation of hemilarynx
T3 
 
Tumor invades more than one subsite of hypopharynx or an adjacent site, with fixation of hemilarynx
T4 
 
Tumor invades adjacent structures., e.g., cartilage or soft tissues of neck

Source: Beahrs OH, Henson DE, Hutter RVP, Kennedy BJ. AJCC Manual for Staging of Cancer, 4th ed. Philadelphia: Lippincott-Raven, 1992; with permission of the American Joint Committee on Cancer, Chicago, Illinois.


Large primary tumors of the nasopharynx obstruct the choanae and nasal airway and can lead to nasal obstruction as well as to epistaxis. Superior extension via the foramen lacerum into the cranium can lead to cranial nerve involvement. Most commonly, cranial nerve VI is the first to be involved with resulting lateral rectus muscle palsy and diplopia. Ophthalmoplegia can occur from involvement of cranial nerves III and IV. High neck and facial pain signifies involvement of cranial nerve V. As the tumor enlarges, cranial nerves VII, IX, X, and XI can be affected (Figs. 13-24, 13-25, 13-27).

The nasopharynx is an extremely complex three dimensional structure with close proximity to the brain, carotid artery, sphenoid sinus, and a variety of other important structures and nerves (Fig. 13-21). It is involved in breathing, deglutition, and phonation. Hence, it is imperative that a surgeon operating in this area be thoroughly familiar with the embryologic, anatomic, and physiologic aspects of the nasopharyx. This avoids potentially disastrous complications.

Oropharynx-Laryngopharynx

The next two regions of the pharynx to be discussed are the oropharynx, continuous with the oral cavity above, and the laryngopharynx, continuous with the esophagus below. The pharynx is a myofascial framework enclosing the pharyngeal lumen and its contents. The external surfaces of the pharynx make up the portions of the borders of important deep neck spaces which are involved in various disease processes. Understanding the anatomy and relationships of the pharynx is important in making sound judgments regarding surgical approaches to the pharynx and adjacent structures.

The following section discusses the anatomy of the pharynx, first describing the myofascial framework. Then we describe the important structures traversing this framework en route to the pharynx, the structures constituting the oropharynx and laryngopharynx, and the important structures bordering the pharynx.

Myofascial Framework

The pharyngeal wall is composed of stratified squamous epithelium, which covers the internal surface of the myofascial layer. This layer extends from the skull base superiorly to the level of the inferior border of the cricoid cartilage inferiorly (Fig. 13-8). This myofascial layer is composed of three paired U-shaped muscles that open anteriorly: the superior, middle, and inferior pharyngeal constrictor muscles (Figs. 13-18, 13-28). These muscles form a telescoping structure with the lower muscles overlapping the upper muscles at the inferior border. All three sets of muscles insert posteriorly on a midline posterior pharyngeal raphe, suspending superiorly from the pharyngeal tubercle of the basiocciput.


These paired pharyngeal constrictor muscles are covered internally and externally by fascial layers. Internally, the constrictor muscles are covered by the pharyngobasilar fascia, which is thick superiorly and thin inferiorly and covers the muscles the length of the pharynx. Superiorly, the pharyngobasilar fascia attaches to the pharyngeal tubercle of the occiput (Fig. 13-28), extends along the petrous portion of the temporal bone, and attaches anteriorly to the medial pterygoid plate (Fig. 13-14) and the pterygomandibular raphe. The upper, thick portion of this fascia suspends the superior constrictor muscle from the skull base. The external surface of the muscle is covered by the buccopharyngeal fascia. This fascia covers the pharynx at the level of the superior constrictor muscle and fuses below this level with the middle layer of deep cervical fascia. This third fascia forms the remainder of the external fascial covering of the pharynx.

The superior pharyngeal constrictor muscles originate from the medial pterygoid plate and pterygomandibular raphe anteriorly. Their fibers extend posteriorly in a horizontal and slightly superior and inferior direction to insert on the posterior midline pharyngeal raphe (Fig. 13-18). These muscles surround the oropharynx.

The middle pharyngeal constrictor muscles originate anteriorly from the greater and lesser cornua of the hyoid bone (Fig. 13-28). Their fibers extend posteriorly in three separate groups (superior, middle, and inferior) to attach on the posterior midline raphe (Fig. 13-18). The middle constrictors are at the level bridging the junction between the lower oropharynx and upper laryngopharynx.

The inferior pharyngeal constrictor muscles are the thickest of the pharyngeal constrictors and the best developed. These arise anteriorly from the oblique line of the thyroid and cricoid cartilages (Fig. 13-28). They then extend posteriorly in a horizontal, superior, and inferior direction to insert on the posterior midline raphe. The cephalic portion of the inferior constrictor muscle is termed the cricopharyngeus muscle. The cricopharyngeus muscle forms the upper esophageal sphincter. It extends from the cricoid cartilage in a horizontal direction and interdigitates with the transverse esophageal muscle layer.

Intervals between the overlapping layers of pharyngeal constrictor muscles are traversed by structures entering the pharynx. The interval between the superior and middle constrictor muscles is traversed by the stylopharyngeus muscle (Fig. 13-18). This muscle originates from the styloid process and extends inferiorly and anteriorly in an oblique fashion to attach to the medial aspect of the middle constrictor muscle. The glossopharyngeal nerve supplies sensory innervation to the base of the tongue and pharynx and also traverses this interspace (Fig. 13-24). The glossopharyngeal nerve and the lingual artery course together, running deep to the hyoglossus muscle (Fig. 13-28). The stylohyoid ligament, which attaches to the lesser cornu of the hyoid bone, also traverses this interval between the superior and middle pharyngeal constrictor muscles. Lying at the inferior pole of the palatine tonsil, the interval provides a pathway of extension for an infectious process from the peritonsillar area to the parapharyngeal space, lateral to the superior constrictor muscle.

The interval between the middle and inferior pharyngeal constrictor muscles is occupied by the thyrohyoid membrane (Fig. 13-28). The structures traversing this membrane include the internal laryngeal nerve and superior laryngeal artery and vein (Fig. 13-24). The internal branch of the superior laryngeal nerve enters the thyrohyoid membrane and supplies sensory innervation to the supraglottic larynx and the piriform recess mucosa. The external branch of the superior laryngeal nerve continues inferiorly, lateral to the constrictor muscles, and accompanies the superior thyroid vessels (Fig. 13-24) to innervate the cricothyroid muscle (Fig. 13-28). The internal branch of the superior laryngeal nerve penetrates the thyrohyoid membrane approximately 1 cm inferior and medial to the greater cornu of the hyoid bone. Infiltration of local anesthetic in this area will create a superior laryngeal nerve block and anesthetize the laryngopharynx and supraglottic larynx. This is also the area of the thyrohyoid membrane where an external laryngocele will extend from the endolaryngeal cavity to the extralaryngeal space.

The interval between the inferior constrictor muscles and the transverse fibers of the esophageal muscle transmits a neurovascular bundle. This bundle includes the recurrent laryngeal nerve (Fig. 13-29). This nerve supplies sensory innervation to the glottis and subglottis and motor innervation to the intrinsic laryngeal muscles except the cricothyroid muscle. Also in this bundle are the inferior laryngeal artery and vein, branches of the thyrocervical trunk of the subclavian vessels.


The innervation of the pharyngeal muscles is from the pharyngeal plexus (Fig. 13-24). This is composed of the pharyngeal branches of the glossopharyngeal and vagus nerves. The glossopharyngeal nerve supplies only the stylopharyngeus muscle. The vagal contribution supplies all the other muscles, including the muscles of the soft palate (Fig. 13-30), with the exception of the tensor palatini muscle, which is supplied by the mandibular branch of the trigeminal nerve (Fig. 13-25). The inferior constrictor muscle also receives innervation from the external branch of the superior laryngeal nerve (Fig. 13-24). The cricopharyngeus muscle may receive some innervation from the recurrent laryngeal nerve. Sensory innervation of the pharynx is supplied by the glossopharyngeal nerve through the pharyngeal plexus. This supplies the mucosa of the oropharynx and laryngopharynx with the exception of the piriform recess mucosa. The piriform recess mucosa receives its innervation from the internal branch of the superior laryngeal nerve, which traverses the submucosa in the anterior wall of the piriform recess (Fig. 13-16).


The vascular supply of the pharyngeal walls is from the ascending pharyngeal artery and the superior thyroid artery, branches of the external carotid artery (Fig. 13-24). The inferior thyroid artery, a branch of the thyrocervical trunk, also provides arterial supply to the laryngopharynx. The venous drainage of the pharynx is through the pharyngeal plexus on the posterior surface of the pharynx. This drains into the pterygoid plexus, the superior and inferior thyroid veins, the facial vein, and directly into the internal jugular vein (Fig. 13-31).

The lymphatic drainage of the pharynx varies depending on the anatomic level. The posterior drainage is through the retropharyngeal lymph nodes (nodes of Rouvier), located behind the pharynx at the level of the carotid bifurcation. Drainage of the lateral pharyngeal structures is to the jugulodigastric and midjugular lymph nodes in the deep jugular chain (Fig. 13-26).

Surgical Considerations

Zenker's diverticulum (Fig. 13-32) may form in the area of Killian's dehiscence (Fig. 13-29), an area of weakness between the inferior constrictor muscle and the fibers of the cricopharyngeus muscle. It is usually on the left side. This is a pulsion diverticulum. It results from increased intraluminal pharyngeal pressures above the level of the cricopharyngeus and increased cricopharyngeal muscle pressures. This causes a gradual weakening of this area and herniation of mucosa and submucosa through the weakened area to form a diverticulum. This problem is usually remedied by performing a cricopharyngeal myotomy with or without resection or suspension of the herniated mucosa.

Oropharynx

The oropharynx is a continuation of the oral cavity anteriorly, the nasopharynx superiorly, and the laryngopharynx inferiorly (Fig. 13-8). It is located at approximately the level of the 2nd and 3rd cervical vertebrae. Its boundaries extend superiorly from the junction of the hard and soft palate (Fig. 13-8, 13-16) to the inferior margin at the level of the plane of the hyoid bone. Anteriorly, it extends to the junction of anterior and posterior regions of the tongue at the level of the circumvallate papillae (Fig. 13-16).

The oropharynx contains the:

 

Soft palate and uvula

Palatine tonsils and tonsillar fossae

Base of tongue

Valleculae

Lateral and posterior oropharyngeal walls

Soft Palate

The soft palate (Figs. 13-8, 13-16, 13-30) is an essential muscular structure which extends from the level of the hard palate (Fig. 13-8) anteriorly to a midline protuberance, the uvula, posteriorly. Laterally, the soft palate blends with the tonsillar area. The soft palate prevents nasopharyngeal reflux of air and food by closing off the oropharynx from the nasopharynx during speech and swallowing.

The soft palate is composed of stratified squamous mucosa which covers a muscular framework of the following five muscles:

 

Levator veli palatini

Tensor veli palatini

Musculi uvulae

Palatoglossus

Palatopharyngeus

Except for the tensor veli palatini, these muscles are innervated by the vagus nerve to the pharyngeal plexus.

The levator veli palatini muscle (Figs. 13-17, 13-30) forms most of the bulk of the soft palate. It arises from the floor of the petrous portion of the temporal bone and medial portion of the cartilaginous eustachian tube, medial to the pharyngobasilar fascia. It travels inferomedially in an oblique fashion to fuse with the contralateral muscle in the posterior portion of the soft palate.

The tensor veli palatini muscle (Fig. 13-17) is the only soft palate muscle innervated by the mandibular branch of the trigeminal nerve rather than the vagus nerve. It arises from the medial pterygoid plate (Fig. 13-14), spine of the sphenoid bone, and lateral portion of the cartilaginous eustachian tube, lateral to the pharyngobasilar fascia. It descends inferiorly to hook around the hamulus of the pterygoid bone (Fig. 13-30) and extends medially as a narrow tendon to insert on the posterior hard palate as the palatine aponeurosis. This muscle functions to laterally tense the palate and also to open the eustachian tube orifice. Children with cleft palates have poor function of the tensor veli palatini muscle, due to the muscle's midline dehiscence. This results in poor eustachian tube opening and chronic middle ear effusions. The eustachian tube dysfunction improves after palatal surgical repair.

The musculi uvulae (Figs. 13-17, 13-30) arise from the posterior hard palate and palatine aponeurosis on each side of the midline, extend posteriorly, and fuse as they form the uvula (Fig. 13-17). These function to draw the uvula upward and forward. Bifidity or notching of the uvula due to failure of these muscles to fuse indicates a submucous cleft of the palate. Care should be taken when performing adenoidectomy to avoid postoperative velopharyngeal insufficiency. Palpation of the palate is necessary to insure absence of submucous clefting even in the absence of a notching of the uvula.

The palatoglossus muscle (Figs. 13-30, 13-33) forms the anterior tonsillar pillar, creating the anterior border of the tonsillar fossa and demarcating the anterior margin of the lateral oropharynx. It is a thin muscle arising from the inferior portion of the soft palate where it fuses to the contralateral palatoglossus muscle, and projects inferiorly to attach to the lateral and dorsal tongue. It functions to draw the palate down and to narrow the pharynx.

The palatopharyngeus muscle (Figs. 13-17, 13-30, 13-33) forms the posterior tonsillar pillar and part of the posterior portion of the tonsillar fossa. It arises as two heads from the hard palate and palatine aponeurosis and more posteriorly from the contralateral palatopharyngeus muscle. The muscle inserts on the fascia of the lower constrictor muscles. In addition to elevating the pharynx, the palatopharyngeus muscles function to draw the palate down and to narrow the pharynx.

Blood supply of the soft palate is from the lesser palatine arteries (Fig. 13-25) and branches of the maxillary artery, which travel with the nerve though the lesser palatine foramen. Sensory innervation is through the lesser palatine branches of the maxillary division of the trigeminal nerve.

Tonsils (Palatine Tonsils)

The palatine tonsils (Figs. 13-8, 13-10, 13-16, 13-17), commonly referred to as the tonsils, are lymphatic structures containing indentations called crypts. The tonsils reside in the tonsillar fossa, which is bounded anteriorly by the palatoglossal arch (Fig. 13-16) and posteriorly by the palatopharyngeal arch. The arches contain the muscles of their corresponding names and are also referred to as the anterior and posterior tonsillar pillars, respectively (Fig. 13-33). The tonsillar fossa is bounded superiorly by the soft palate, and inferiorly by the base of tongue mucosa. Tonsillar tissue frequently extends superiorly and inferiorly into these structures.

Laterally, the tonsil has a capsule that is formed by the pharyngobasilar fascia. A layer of loose connective tissue separates the capsule from the superior constrictor muscle. This potential space is the peritonsillar space. Spread of infection from the tonsils into this area results in a peritonsillar abscess, requiring transoral aspiration or incision and drainage. Due to the proximity of the medial pterygoid muscle to the peritonsillar space (the medial pterygoid muscle is located lateral to the superior constrictor muscle) (Fig. 13-18), peritonsillar abscesses present with trismus and bulging of the tonsil and soft palate medially and inferiorly.

The inferior pole of the tonsil lies at the level of the interspace between the superior and middle constrictor muscles (Figs. 13-16, 13-18). Extension of a peritonsillar abscess laterally in this interspace through the buccopharyngeal fascia results in a parapharyngeal space abscess (Fig. 13-34). This results in more intense trismus because of the direct irritation of the medial pterygoid muscle. This also places the great vessels of the neck at risk due to their location in the parapharyngeal space. Inferior dissection of infection through the carotid sheath may result in mediastinitis. The glossopharyngeal nerve (Figs. 13-33, 13-34) also traverses this interspace between the superior and middle constrictor muscles at the inferior pole of the tonsil and is at risk in deep dissection during a tonsillectomy.


Five branches of the external carotid artery system supply blood to the tonsils. The main supply is inferiorly from the tonsillar branch of the facial artery (Fig. 13-34). The ascending pharyngeal, dorsal lingual, ascending palatine branch of the facial artery, and descending palatine artery also supply the tonsils. Lymphatic drainage of the tonsils is primarily to the jugulodigastric lymph nodes (Fig. 13-26).

Sensory innervation of the tonsil is through the glossopharyngeal nerve and from the greater and lesser palatine branches of the maxillary branch of the trigeminal nerve (Fig. 13-25). The phenomenon of referred otalgia (Fig. 13-35) in cases of tonsillitis, tumors of the tonsil, and after tonsillectomy is mediated through common projections of the oropharyngeal fibers of the glossopharyngeal nerve and Jacobsen's nerve. Jacobsen's nerve (Figs. 13-24, 13-35) is the tympanic branch of the glossopharyngeal nerve that innervates the middle ear mucosa.

Base of Tongue

The base of tongue (Fig. 13-17) is the posterior one-third of the tongue which lies posterior to the circumvallate papillae (Fig. 13-16) and foramen cecum, the area of origination of the thyroid gland. It extends posteriorly to the level of the valleculae, and laterally continues with the floor of mouth mucosa at the inferior pole of the tonsils (Fig. 13-8). The base of tongue contains submucosal lymphatic collections referred to as lingual tonsils, which, together with the palatine tonsils and adenoids (pharyngeal and tubal tonsils), form the previously described Waldeyer's ring (Fig. 13-10), a first line of immunologic defense. This is also an uncommon area of primary lymphoma presentation.

The sensory innervation of the base of tongue is through the glossopharyngeal nerve, which supplies general visceral afferent fibers and special visceral afferent fibers for taste. Base of tongue musculature is innervated by the hypoglossal nerve (Fig. 13-24). Arterial supply of the base of tongue is through the lingual arteries. The base of tongue has a rich lymphatic drainage system primarily to the jugulodigastric lymph nodes (Fig. 13-26). Lymphatic drainage to both sides of the neck is the rule. This necessitates addressing both the ipsilateral and contralateral neck when treating tumors of the base of tongue, due to the likelihood of bilateral metastases.

The base of tongue extends posteriorly into paired concavities (valleculae) along the base of the lingual surface of the epiglottis (Figs. 13-8, 13-16). The valleculae are separated in the midline by a median glossoepiglottic fold and bounded laterally by lateral glossoepiglottic folds (pharyngoepiglottic folds) (Fig. 13-16), which attach the epiglottis to the base of tongue.

The remainder of the oropharynx consists of the posterior pharyngeal wall and lateral pharyngeal wall posterior to the posterior tonsillar pillar.

Laryngopharynx (Hypopharynx)

The laryngopharynx is the longest section of the pharynx, extending from the level of the hyoid bone (Fig. 13-8) superiorly to the inferior border of the cricoid cartilage at the level of the sixth cervical vertebra. It is wider superiorly and narrows inferiorly. The upper part of the laryngopharynx is the most caudal portion of the common aerodigestive tract. The lower part, including the piriform recessses and postcricoid area, is the beginning of the separated digestive tract that leads to the esophagus. The laryngopharynx is divided into the following three separate areas (Fig. 13-16):

 

Posterior pharyngeal wall

Piriform recesses

Postcricoid area

The posterior pharyngeal wall extends from the level of the hyoid bone to the inferior border of the cricoid cartilage and is continuous laterally with the lateral wall of the piriform recesses.

The piriform recessses are funnel-shaped structures that are open posteriorly to the remainder of the pharynx. They are bounded anteriorly and laterally by the lamina of the thyroid cartilage, and medially by the aryepiglottic fold, arytenoid cartilage, and cricoid cartilage (Fig. 13-8). The superior extent is at the level of the pharyngoepiglottic fold (Figs. 13-16, 13-17), and the inferior apex is at the level of the cricopharyngeus muscle (Figs. 13-29, 13-32). This apex approximates the level of the laryngeal ventricle.

The postcricoid area includes the mucosa covering the area from the posterior cricoarytenoid joint superiorly to the inferior border at the cricoid cartilage (Fig. 13-8). It is continuous laterally with the medial wall of the piriform recessses and inferiorly with the esophagus.

Sensory innervation of the laryngopharynx is from the glossopharyngeal (Fig. 13-24) and vagus nerves. The posterior pharyngeal wall is innervated by the fibers of the glossopharyngeal nerve through the pharyngeal plexus. The piriform recessses and postcricoid mucosa are innervated by the internal branch of the superior laryngeal nerve, which runs beneath the mucosa of the anterior piriform recess. Anesthesia of the piriform recesses and larynx can be obtained by topically anesthetizing the piriform recess mucosa or by percutaneous superior laryngeal nerve block at the thyrohyoid membrane (Fig. 13-28). The laryngopharynx is surrounded by the inferior constrictor muscle (Figs. 13-18, 13-28). Motor innervation to this muscle is supplied by the external branch of the superior laryngeal nerve, which runs along the lateral border of the inferior constrictor muscle (Fig. 13-24) with the superior thyroid vascular pedicle.

Previously described, the vascular supply to the laryngopharynx is through the superior and inferior thyroid arteries and their branches (Fig. 13-24). The lymphatic drainage is through the thyrohyoid membrane to jugulodigastric and midjugular lymph nodes (Fig. 13-26), but also involves the retropharyngeal/peritracheal and periesophageal lymph nodes. Tumors of the laryngopharynx commonly present at an advanced stage because the large size of the laryngopharynx allows the malignancy to go unnoticed until obstruction occurs late in the disease process. Tumors present with dysphagia, hemoptysis, voice change due to laryngeal invasion, and commonly as an enlarged metastatic lymph node in the neck. Referred otalgia (Fig. 13-35) is a common presenting symptom of hypopharyngeal malignancies. This is due to the common central projections of the internal branch of the superior laryngeal nerve, which innervates the piriform recess, and Arnold's nerve (the auricular branch of the vagus nerve), which innervates a portion of the posterior external auditory canal. Therefore, otalgia in the absence of the obvious ear pathology is an indication to carefully examine the upper aerodigestive tract for pathology.

Surgical Considerations

Injury to the external branch of the superior laryngeal nerve can occur in thyroidectomy if the superior thyroid neurovascular pedicle is ligated high. Avoid injury to the superior laryngeal nerve when clamping the superior thyroid pedicle by observing the following precaution. Ligate the vascular pedicle at the capsule of the superior pole of the thyroid gland, inferior to the point of divergence of the external branch of the superior laryngeal nerve away from the vascular pedicle, toward the cricothyroid muscle.

 Read an Editorial Comment

Because of the close relationship of the laryngopharynx to the larynx, and the advanced presentation of hypopharyngeal tumors, surgical resection often involves total or near-total laryngopharyngectomy. The propensity for submucosal extension of disease in the esophagus creates tumors that involve the inferior apex of the piriform recess and/or the postcricoid mucosa. These often require esophagectomy in addition to total laryngopharyngectomy to ensure adequate margins of resection in the esophagus. Then total pharyngeal reconstruction can be performed. Use a free jejunal or tubed fasciocutaneous flap in the case of cervical pharyngeal defects. For pharyngoesophageal defects, use gastric pull-up.

Physical Examination of the Oropharynx and Laryngopharynx

Examination of the oropharynx can easily be performed with the use of tongue depressors. Gentle compression of the middle third of the tongue inferiorly with slight anterior traction will allow adequate visualization of the tonsils, anterior base of tongue, soft palate, and posterior pharyngeal wall. For patients with hyperactive gag reflexes, topical anesthetic can be used to improve visualization. Examination of the base of tongue and valleculae require gentle anterior retraction of the tongue with a gauze pad and indirect examination with the use of a laryngeal mirror. The mirror is placed superiorly in the oropharynx with the back of the mirror elevating the soft palate and uvula without contacting the posterior pharyngeal wall to avoid gagging the patient. In addition to visualization, palpation of the tonsils and base of the tongue with the finger is helpful in detecting mucosal and submucosal abnormalities.

Examination of the laryngopharynx and larynx requires use of a laryngeal mirror or a fiberoptic laryngoscope through the nasal cavity. The larynx and vocal cord motion should be evaluated. The piriform recesses can best be visualized with the patient phonating. This brings the aryepiglottic folds and arytenoid cartilages medial, thereby opening the piriform recesses. The presence of saliva pooling within a single piriform recess should raise suspicion of a lesion within that space. The presence of a unilateral paralyzed vocal cord should also raise suspicion of a tumor involving the piriform recess and extending to the paraglottic space. The posterior pharyngeal wall can also be easily visualized with a mirror or flexible laryngoscope.

The postcricoid area is difficult to visualize with either of these techniques and requires direct laryngoscopy under general or topical anesthesia. The laryngopharynx, in general, is best visualized with direct laryngoscopy. The laryngoscope is directly inserted into the vallecula. It can then be slid laterally into the piriform recess, elevating it anteriorly to see the anterior portion of the piriform recess. When the laryngoscope is inserted deeper to the apex of the piriform recess both the medial and lateral walls can be visualized. The laryngoscope can then be rotated medially into the postcricoid area, by lifting the larynx anteriorly to open the postcricoid area and esophageal inlet. The laryngoscope is then moved into the contralateral piriform recess. The posterior pharyngeal wall is also visualized when the larynx is lifted anteriorly by elevating the postcricoid mucosa.

When examining the neck, grasping the thyroid cartilage and moving it from side to side over the top of the cervical spine should produce normal laryngeal crepitus as the cartilage of the larynx rolls over the bony cervical spine. Absence of this laryngeal crepitus suggests a posterior pharyngeal or postcricoid mass that is preventing the cartilage-to-bone contact. This portion of the examination should be performed routinely during evaluation of the larynx and pharynx.

Pharyngeal Relationship to Deep Neck Spaces

The oropharynx has very important relationships to surrounding potential deep neck spaces, including the retrovisceral spaces (Fig. 13-22) and the parapharyngeal space (lateral pharyngeal space). Although not part of the pharynx, these spaces may be involved with pathology that originates in the pharynx or encroaches upon the pharynx. Knowledge of the anatomy of these spaces and their relationship to the pharynx is integral to understanding the surgical approaches to these spaces and the perils and pitfalls of these approaches.

Retrovisceral Space

The area posterior to the pharynx (the retrovisceral space) (Fig. 13-22) can be separated into the following three spaces (Figs. 13-23, 13-27):

 

Retropharyngeal space

Danger space

Prevertebral space

The retropharyngeal space is bounded by the buccopharyngeal fascia anteriorly and by the alar layer of prevertebral fascia posteriorly. Laterally, it is continuous with the parapharyngeal space. The parapharyngeal space extends from the skull base superiorly to the level of the tracheal bifurcation (approximately the level of the fourth thoracic vertebra), where the alar layer of prevertebral fascia fuses with the middle layer of deep cervical fascia. The retropharyngeal space contains lymph nodes (nodes of Rouvier) in addition to connective tissue. Infections and abscesses in the retropharyngeal space are usually unilateral in presentation due to the posterior midline attachment of the midline raphe of the superior constrictor muscle to the prevertebral fascia.

The danger space is bounded anteriorly by the alar fascia and posteriorly by the prevertebral fascia. It extends superiorly from the skull base to the diaphragm inferiorly.

The prevertebral space is bounded anteriorly by the prevertebral layer of prevertebral fascia, posteriorly by the vertebral bodies, and laterally by the transverse processes. It extends superiorly from the skull base to the coccyx inferiorly.

Involvement of these spaces with infection may occur from suppuration of retropharyngeal nodes, penetrating injury, or spread from adjacent spaces. These spaces may be approached either transorally or transcervically.

Parapharyngeal Space (Lateral Pharyngeal Space)

The parapharyngeal, or lateral pharyngeal, space (Figs. 13-27, 13-36) is typically described as an inverted pyramid-shaped space located lateral to the pharynx. Its superior extent is at the skull base, including a small portion of the temporal bone and a fascial connection from the medial pterygoid plate to the spine of the sphenoid medially. It extends inferiorly to the level of the greater cornu of the hyoid bone at its junction with the posterior belly of the digastric muscle. The superior medial border is formed by the fascia of the tensor veli palatini (Fig. 13-27) and medial pterygoid muscles and the pharyngobasilar fascia. Inferiorly, the medial border is formed by the superior constrictor muscle. The anterior border is formed by the pterygomandibular raphe. The lateral boundaries are the medial pterygoid muscle, the mandible, the deep lobe portion of the parotid gland, and a small portion of the digastric muscle posteriorly. The posterior border is the prevertebral fascia.

The parapharyngeal space is divided into a pre- and retrostyloid compartment (Fig. 13-27) by fascia extending from the styloid process to the tensor veli palatini muscle. The pre-styloid compartment contains lymphatic tissue, the internal maxillary artery, and further branches of the mandibular branch of the trigeminal nerve. The retrostyloid compartment contains the carotid artery, internal jugular vein, cranial nerves IX, X, XI, and XII, and the cervical sympathetic chain (Figs. 13-27, 13-36).

Surgical Considerations

Masses or infections in the parapharyngeal space present as a fullness or bulging in the lateral pharyngeal wall, displacing the tonsil medially and/or the soft palate medially and inferiorly with contralateral deviation of the uvula. Trismus is a frequent finding, especially with parapharyngeal space abscesses or large tumors. These are caused by irritation or involvement of the medial pterygoid muscle, which forms the lateral extent of the parapharyngeal space. Infections may spread to the parapharyngeal space from adjacent spaces (retropharyngeal, peritonsillar) or arise primarily from suppurated nodes. Infection or tumors in this space may enter the carotid sheath and place the carotid arteries and the internal jugular vein at risk. Infections may also spread inferiorly in this space through the mediastinum and the carotid sheath. Drainage of parapharyngeal abscesses or removal of tumors in the parapharyngeal space should be performed by external approaches to ensure control of the great vessels and major nerves in the retrostyloid compartment. Do this especially in the case of tumors where the neurovascular structures may be displaced.

Penetrating injuries through the lateral wall of the oropharynx may result in injury to structures in the parapharyngeal space. Injuries that are more posterior result in damage to the carotid artery, internal jugular vein, or upper cranial nerves. Injuries that are more anterior may result in damage to the parotid gland, duct, or intraparotid facial nerve. Patients with these types of injuries require observation and serial neurological examinations or carotid arteriograms to rule out vascular injuries.

We quote Leitner and Johns2 on pharyngolaryngectomy for carcinoma of the posterior pharyngeal wall:

Along with neck dissection, we use an extended posterolateral pharyngectomy which includes the primary site, the retropharyngeal lymph nodes, and the cervical lymph nodes in the resected specimen. T2 and T3 carcinomas can be effectively removed en bloc with the retropharyngeal and neck dissection specimen. Primary closure has been used in all cases, with minimal functional rehabilitation necessary, and postoperative radiotherapy is given to the primary site and both sides of the neck.

Sessions et al.3 wrote about metastasis in hypopharyngeal cancer:

All treatment plans for hypopharyngeal cancer must consider certain facts: The overwhelming majority of these lesions metastasize to cervical lymph nodes, and in the case of the posterior pharyngeal wall, bilateral metastasis is the rule rather than the exception; 40% of posterior pharyngeal wall lesions and probably an equal number of upper pyriform sinus lesions metastasize to the retropharyngeal nodes; in those patients with clinically negative necks, the incidence of occult metastasis is substantial; and between 20% and 30% of pyriform sinus lesions, and probably an equal number of posterior pharyngeal wall lesions, are associated with distant metastasis. Even in the lesser-stage hypopharyngeal lesions, the high rate of regional metastases requires inclusion of the neck(s) in all management plans.

Histology

From outside to inside, the pharyngeal wall is formed by the buccopharyngeal fascia, muscular layer, fibrous layer, and mucosa.

 

The buccopharyngeal fascia is a thin layer covering the epimysium and, for all practical purposes, corresponds to the external part of the epimysium.

The muscular layer (superior, middle, and inferior constrictor muscles) and its fibrous network is described previously in connection with the several parts of the pharynx.

The fibrous layer supports the mucosa that rests on it.

The mucosa of the pharynx may be divided into three parts. The anterior portion consists of ciliated and pseudostratified epithelium. The transitional layer is columnar epithelium. The posterior layer is non-keratinized stratified squamous epithelium. Several mucous glands are present.

Physiology

Coordinated movements of the palatal and pharyngeal muscles take place during both swallowing and speech. As previously mentioned the velum (soft palate and uvula) is instrumental in closing the nasopharynx during speech.

Certain sounds, such as fricatives, require closure of the nasopharynx by the velum. Closure of the velopharyngeal port (sphincter) is a very complex sequence of rapid muscle actions. The soft palate elevates toward the posterior pharynx with the levator veli palatini. The muscles of the uvula draw it upward and forward. The palatoglossus, which forms the anterior tonsillar pillar, narrows the caudal nasopharynx and draws the soft palate down.

Swallowing is a very complex sequence of involuntary events, starting with velopharyngeal closure to prevent reflux. In the first phase of swallowing, the food bolus enters the mouth and the soft palate tenses and elevates. It is then drawn downward to strip the bolus from the valleculae. The tongue projects the bolus from the oropharynx into the laryngopharynx.

The three paired constrictor muscles (Figs. 13-18, 13-28) are important in the second phase of swallowing (pharyngeal phase). This is an involuntary phase that involves the serial contraction of the pharyngeal constrictor muscles in a superior-to-inferior direction to propel a bolus inferiorly.

The cricopharyngeus muscles, unlike the remaining portions of the constrictor muscles, have a tonic level of contraction, allowing them to function as the upper esophageal sphincter. Relaxation of the cricopharyngeus muscle is necessary to allow the passage of a bolus from the pharynx to the esophagus. Failure of the cricopharyngeus muscle to relax results in dysphagia. This may be the result of a neuromuscular disease such as amyotrophic lateral sclerosis, polymyositis, myasthenia gravis, multiple sclerosis, Parkinson's disease, or cerebrovascular accidents. Cricopharyngeal achalasia, which may be idiopathic or the result of gastroesophageal reflux or other etiologies, is failure of the cricopharyngeus muscle to relax.

In the pharyngeal phase of swallowing, the larynx also elevates and moves forward under the base of tongue to aid in protection against aspiration. The epiglottic folds also move caudal and backward and strip the epiglottic valleculae of all food material.

The esophageal phase of swallowing (the last stage), involves a series of involuntary sequential peristaltic contractions as the food bolus is moved into the stomach.

Surgical Complications (Recognition and Treatment)

Tonsillectomy and Adenoidectomy

Complications after adenotonsillectomy may be immediate or delayed. Immediate complications include airway problems and bleeding. Patients with severe obstructive sleep apnea and hypotonia may develop respiratory compromise in the first 24 hours after surgery. They require close telemetry and respiratory support.

The most common delayed complication is postoperative hemorrhage. Bleeding can occur up to 2 weeks after surgery but usually occurs within 7 to 10 days. The postoperative bleed rate ranges from 1% to 5% of cases and is more common with the electrocautery technique. Treatment requires prompt recognition, fluid resuscitation, and emergent cauterization of the bleeding vessels. An understanding of the vascular supply of the tonsil is helpful (Fig. 13-34).

Other complications include velopharyngeal incompetence (VPI), Grisel's syndrome, and nasopharyngeal stenosis. Hypernasality is a consequence of incompetence of the velum after surgery. This may occur after excessive removal of the tonsillar pillars or more commonly after adenoidectomy in a patient who has an occult submucous cleft palate. It is important to always palpate the hard palate in the operating room for a submucous cleft which is felt as a ridge in the bone. If found, only a partial (superior) adenoidectomy should be performed.

Irritation and spasm of the prevertebral muscles can occasionally cause atlantoaxial subluxation, known as Grisel's syndrome. Treatment includes nonsteroidal anti-inflammatory agents, immobilization, and soft collar. If true subluxation has occurred, surgical reduction may be necessary.

Nasopharyngeal stenosis (Fig. 13-19) is thought to be caused by the overzealous removal and/or cauterization of inferior lateral adenoid tissue and damage to the posterior tonsillar pillar. This complication is associated with electrocautery and laser adenotonsillectomy. Presenting symptoms range from mild hyponasal speech to severe airway obstruction. Prevent this complication by using proper techniques, including careful dissection, preservation of pillar anatomy, and judicious excision of the lateral adenoid bands. Repairs are complicated and never lead to a perfect nasopharyngeal airway.

Uvulopalatopharyngoplasty (UPPP)

Complications of UPPP are the result of excessive removal of soft palate tissue or excessive scarring. The goal of a UPPP is to remove redundant pharyngeal tissue and shorten the palate in order to enlarge the oropharyngeal inlet and thereby to correct obstructive sleep apnea syndrome. This is best performed by removing the tonsils (if present), resecting excessive anterior tonsillar pillar mucosa, conservatively removing posterior tonsillar pillar mucosa, and resecting the uvula and posterior soft palate. The extent of removal of the tonsillar pillar mucosa should be enough to eliminate mucosal redundancy and allow slight tenting of the posterior pharyngeal wall mucosa at the completion of the closure.

Velopharyngeal insufficiency, a complication of UPPP, results from excessive removal of the soft palate. This results in a soft palate that is not long enough to contact the posterior pharyngeal wall and separate the oropharynx from the nasopharynx during speech and swallowing. This causes hypernasal speech and nasal regurgitation of liquids. These problems can be avoided by conservative removal of soft palate tissue. At the time of UPPP, the line of resection of the soft palate should not extend anterior to the point of contact between the soft palate and the posterior pharyngeal wall, usually at the level of a dimple at the base of the uvula. Treatment of VPI is difficult, initially involving speech therapy, but usually requiring augmentation of the posterior pharyngeal wall or soft palate (pharyngeal flap).

Another possible complication of UPPP is nasopharyngeal stenosis. Removal of the tonsils and soft palate resection create a nearly circumferential defect of the oropharynx. This can contract and narrow the oropharyngeal inlet. It is more likely if excessive posterior tonsillar pillar and lateral oropharyngeal mucosa are removed, resulting in posterior retraction of the lateral oropharyngeal closure and narrowing of the inlet. This complication can be avoided by judicious removal of posterior tonsillar pillar mucosa with anterior mobilization of the posterior and lateral oropharyngeal mucosa (or, if possible, by completely avoiding removal). This allows an anteriorly placed suture line at the level of the incision of the anterior tonsillar pillar mucosa. Also, complete mucosal closure of the palate and tonsillar fossae will reduce the possibility of circumferential scarring. Good surgical technique and judicious tissue removal is the key to avoiding complications in UPPP.

Pharyngeal Tumor Surgery (Pharyngolaryngectomy)

Complications following pharyngeal tumor removal are related to the effects of tissue removal on function and the limitations of reconstruction. As previously described, the swallowing mechanism is a finely coordinated series of events that allow the orderly passage of a bolus from the oral cavity to the stomach. Surgical removal of portions of the pharynx and reconstruction with distant tissue flaps that are insensate result in dysphagia due to disordered pharyngeal movement and pharyngeal insensitivity. In some instances the swallowing mechanism may be significantly disrupted. This results in inability to protect the airway and leads to aspiration. This problem is initially treated with speech therapy to institute compensatory strategies such as head tilt or turn or adding thickening products to the food to overcome the swallowing dysfunction. In some cases, a permanent gastrostomy tube and cessation of oral food intake is necessary.

Other complications of pharyngeal tumor surgery involve fistula and stenosis. A pharyngocutaneous fistula results when saliva leaks through the pharyngeal closure into the neck and creates a passage to the skin. This may occur as a result of technical error such as incomplete mucosal closure or tension at the suture line resulting in ischemic necrosis and breakdown or infection. This is best avoided by meticulous watertight wound closure under no tension. Most pharyngocutaneous fistulas will close with conservative treatment, pressure dressings of packing of the neck, and avoidance of oral feeding, but occasionally flap closure may be necessary.

Pharyngeal stenosis following tumor surgery may occur due to closure with inadequate amount of pharyngeal tissue or secondary to circumferential scarring. In general, primary pharyngeal closure may be performed as long as the closure allows passage of the index finger or larger object through the reconstructed lumen. If this requirement cannot be met, closure should be augmented with a flap. Circumferential scarring is more of a problem with total pharyngeal reconstruction and can be avoided by procedures to break up a circumferential closure, such as V-shaped inset flaps. If stenosis does occur, then initial treatments should involve attempts at dilatation which can be done periodically as needed. If this fails, flap augmentation to enlarge the pharyngeal lumen is necessary.

Recommended Reading

Adams GL. Malignant neoplasms of the hypopharynx. In Cummings CW (ed). Otolaryngology - Head and Neck Surgery (2nd ed). St Louis: Mosby Year Book, 1993, pp. 1955-1973.

Byrne MN. Neck spaces and fascial planes. In Lee KJ (ed). Essential Otolaryngology: Head and Neck Surgery (5th ed). New York: Medical Examination Publishing, 1991, pp. 405-422.

Clemente CD. Anatomy: A Regional Atlas of the Human Body (4th ed). Baltimore: Williams & Wilkins, 1997.

Cummings CW. Otolaryngology - Head and Neck Surgery. St Louis: Mosby, 1986.

Graney DO, Petruzzelli GJ, Myers EN. Anatomy. In Cummings CW (ed). Otolaryngology - Head and Neck Surgery (2nd ed). St. Louis: Mosby Year Book, 1993, pp. 1101-1112.

Hollinshead WH. Anatomy for Surgeons: The Head and Neck (3rd ed). New York: JB Lippincott, 1982, pp. 389-441.

Hollinshead WH, Rosse C. Pharynx and larynx. In Hollinshead WH, Rosse C. Textbook of Anatomy (4th ed). New York: Harper and Row, 1985, pp. 987-997.

Hollinshead WH, Rosse C. Skull, face and jaws. In Hollinshead WH, Rosse C. Textbook of Anatomy (4th ed). New York: Harper and Row, 1985, p. 899.

Hollinshead WH, Rosse C. The neck. In Hollinshead WH, Rosse C. Textbook of Anatomy (4th ed). New York: Harper and Row, 1985. pp. 821-851.

Jacobs IN, Gray R, Wyly B. Approach to branchial pouch anomalies that cause airway obstruction during infancy. Otolaryngology-Head and Neck Surgery 118(5):682-685, 1998.

Lore JM Jr. An Atlas of Head and Neck Surgery (2nd ed). Philadelphia: WB Saunders, 1988.

McLaughlin KE, Jacobs IN, Todd NW, Gussack GS, Carlson G. Management of nasopharyngeal and oropharyngeal stenosis in children. Laryngoscope 107(10):1322-1331, 1997.

Olsen KD. Tumors and surgery of the parapharyngeal space. Laryngoscope 1994;104(Suppl):1-28.

Robbins KT. Pocket Guide to Neck Dissection Classification and TNM Staging of Head and Neck Cancer. Alexandria, Va: American Academy of Otolaryngology - Head and Neck Surgery Foundation, 1991.

Skandalakis JE, Gray SW, Todd NW. The pharynx and its derivatives. In Skandalakis JE, Gray SW. Embryology for Surgeons (2nd ed). Baltimore: Williams and Wilkins, 1994, pp. 17-64.

Sistrunk WE. The surgical treatment of cysts of the thyroglossal tract. Ann Surg 1920;71:121.

Thawley SE, O'Leary M. Malignant neoplasms of the oropharynx. In Cummings, CW (ed). Otolaryngology - Head and Neck Surgery (2nd ed). St Louis: Mosby Year Book, 1993, pp. 1306-1354.

Tobias PV. The nasopharynx: review of structure and development with notes of speech, pharyngeal hypophysis chordoma and dens. J Dent Assoc S Afr 1981;36:765-778. [PubMed: 6952607]

References

1. Martin H. Surgery of Head and Neck Tumors. New York: Hoeber-Harper, 1957, p. 115.

2. Leitner YB, Johns ME. Extended posterolateral pharyngectomy for carcinoma of the posterior pharyngeal wall. Am J Otolaryngol 1982;3:383-387. [PubMed: 7158703]

3. Sessions RB, Harrison LB, Forastiere AA. Tumors of the larynx and hypopharynx. In: DeVita VT Jr, Hellman S, Rosenberg SA (eds). Cancer: Principles and Practice of Oncology (6th ed). Philadelphia: Lippincott Williams & Wilkins, 2001, pp. 861-886.

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