Anatomy and Physiology of the Velopharyngeal Mechanism

Jamie L. Perry, Ph.D.1

ABSTRACT

Understanding the normal anatomy and physiology of the velopharyngeal mechanism is the first step in providing appropriate diagnosis and treatment for children born with cleft and . The velopharyngeal mechanism consists of a muscular valve that extends from the posterior surface of the (roof of ) to the posterior pharyngeal wall and includes the velum (), lateral pharyngeal walls (sides of the ), and the posterior pharyngeal wall (back wall of the throat). The function of the velopharyngeal mechanism is to create a tight seal between the velum and pharyngeal walls to separate the oral and nasal cavities for various purposes, including speech. Velopharyngeal closure is accomplished through the contraction of several velopharyngeal muscles including the , musculus uvulae, superior pharyngeal con- strictor, palatopharyngeus, palatoglossus, and salpingopharyngeus. The tensor veli palatini is thought to be responsible for function.

KEYWORDS: Anatomy, physiology, velopharyngeal muscles, cleft

palate anatomy Downloaded by: SASLHA. Copyrighted material.

Learning Outcomes: As a result of this activity, the reader will be able to (1) list the major muscles of the velopharyngeal mechanism and discuss their functions; (2) list the sensory and motor innervation patterns for the muscles of the velopharyngeal mechanism; and (3) discuss the variations in velopharyngeal anatomy found in an unrepaired cleft palate.

Understanding the normal anatomy and and treatment for children born with cleft lip physiology of the velopharyngeal mechanism is and palate. Most of the diagnostic and therapy the first step in providing appropriate diagnosis approaches are based on a strong foundation of

1Department of Communication Sciences and Disorders, Guest Editor, Ann W. Kummer, Ph.D., CCC-SLP, Illinois State University, Normal, Illinois. ASHA-F. Address for correspondence and reprint requests: Jamie Semin Speech Lang 2011;32:83–92. Copyright # L. Perry, Ph.D., Department of Communication Sciences 2011 by Thieme Medical Publishers, Inc., 333 Seventh and Disorders, Illinois State University, 208 Rachel Avenue, New York, NY 10001, USA. Tel: +1(212) 584- Cooper, Normal, IL 61790 (e-mail: [email protected]). 4662. Communication Disorders Related to Cleft Palate, DOI: http://dx.doi.org/10.1055/s-0031-1277712. Craniofacial Anomalies, and Velopharyngeal Dysfunction; ISSN 0734-0478. 83 84 SEMINARS IN SPEECH AND /VOLUME 32, NUMBER 2 2011

the underlying anatomy. In addition, this pop- resonance image (MRI) of the velopharyngeal ulation continually presents with changes in the mechanism at rest and during speech produc- anatomy and physiology as the head and neck tion. The orifice or gap behind the velum is anatomy develops across childhood and called the ‘‘velopharyngeal port.’’ This is the through adolescence. Being able to identify distance that the velum and pharyngeal walls the important structures and know how these must overcome to have complete closure, such relate to normal and abnormal speech produc- as during speech and . Histological tion is a critical part of our ongoing evaluation studies show that the velum consists of a for such individuals. Although cleft palate mixture of tendinous, muscular, adipose, con- anatomy includes facial, oral, nasal, and phar- nective, and glandular tissue along the velar yngeal anatomy, the focus for this article is on length.3,4 The anterior two-thirds of the velum the structures and muscles related to the nor- appears to be consistent in its composition mal velopharyngeal mechanism as these struc- compared with the posterior one-third, which tures and muscles have the greatest impact on shows greater variability across individuals. speech and resonance. The purpose of this This demonstrates the importance of the ante- article is to provide an overview of normal rior two-thirds in providing the functional anatomy and physiology of the velopharyngeal components to the velum during velopharyng- mechanism and to provide a brief discussion of eal closure.5 how the anatomy is altered when there is a cleft palate. Function The function of the velopharyngeal mechanism VELOPHARYNGEAL MECHANISM is to create a tight seal between the velum and pharyngeal walls to separate the oral and nasal Orientation cavities. During speech, normal velopharyngeal The velopharyngeal mechanism consists of a closure is necessary to be able to produce oral muscular valve that extends from the posterior speech phonemes. Only three sounds in the surface of the hard palate (roof of mouth) to the English language, /m/, /n/, /ng/, are produced posterior pharyngeal wall.1 The mechanism with an open velopharyngeal port. includes the velum (soft palate), lateral phar- The velum extends from the posterior yngeal walls (sides of the throat), and the nasal spine of the hard palate to the uvula.

posterior pharyngeal wall (back wall of the During nasal breathing, the oral surface is Downloaded by: SASLHA. Copyrighted material. throat).2 Fig. 1 shows a midsagittal magnetic down and rests against the back of the

Figure 1 Midsagittal magnetic resonance imaging of velopharyngeal mechanism at rest (A) and during speech production (B). The white arrow is pointing at the velar eminence during elevation. PPW, posterior pharyngeal wall. ANATOMY AND PHYSIOLOGY OF THE VELOPHARYNGEAL MECHANISM/PERRY 85

(Fig. 1A). During production of oral speech to contraction of the inferior fibers of the sounds, the velum is elevated and retracted to superior constrictor muscle.6 It can best be make complete contact against the posterior viewed on the lateral view of videofluoroscopy pharyngeal wall. As seen in Fig. 1B, when the but can also be seen with nasopharyngoscopy velum elevates it creates a ‘‘knee’’ or eminence when there is a large velopharyngeal opening. as it bends against the posterior pharyngeal wall It can even be viewed through an intraoral (white arrow on Fig. 1B). This creates a tight examination in some cases. Passavant’s ridge seal to redirect the sound and airflow into the is seen in children with a repaired cleft palate mouth instead of the . and also in individuals with normal anatomy. Closure of the velopharyngeal mechanism The existence of a Passavant’s ridge does not is primarily accomplished by retraction and mean that contact is achieved against this ridge. elevation of the velum. Movement of the phar- In most cases, the ridge is too low to assist with yngeal walls, however, also contributes to ve- velopharyngeal closure. lopharyngeal closure. Lateral pharyngeal wall Three basic types of closure have been movement toward the midline and anterior identified across individuals with normal movement of the posterior pharyngeal wall speech and also those with repaired cleft palate. help to create a sphincterlike closure pattern. Closure patterns include coronal, where the Some individuals may create velar contact closure occurs primarily due to the action of against an enlarged adenoid pad. This is more the velum, with less contribution of the lateral commonly observed in children before adenoid pharyngeal walls; circular, where all structures involution occurs during adolescence. Fig. 2 come together as ‘‘purse string’’; and sagittal, demonstrates a midsagittal MRI of this ad- where lateral pharyngeal wall movement is the enoid-to-velar contact in a 4-year-old child major component of closure.2,7 Passavant’s with normal anatomy. ridge is commonly seen with the circular pat- Some individuals have what is called a tern of closure. Closure pattern is best observed ‘‘Passavant’s ridge.’’ When a Passavant’s ridge through nasopharyngoscopy, which provides a is present, it appears as a shelflike structure that view from the top or nasal surface of the velum. bulges forward during speech and then disap- Fig. 3 demonstrates a coronal closure pattern pears at rest. Passavant’s ridge is felt to be due observed in an adult male in which the major movement is an upward and backward move- ment of the velum accompanied by a secondary

component of lateral pharyngeal wall move- Downloaded by: SASLHA. Copyrighted material. ment. This is the most common pattern of closure observed in individuals with normal anatomy.

NORMAL VELOPHARYNGEAL MUSCULATURE There are several velopharyngeal muscles, in- cluding the levator veli palatini, musculus uvu- lae, tensor veli palatini, superior pharyngeal constrictor, palatopharyngeus, palatoglossus, and salpingopharyngeus. These muscles are described below.

Levator Veli Palatini Figure 2 Midsagittal magnetic resonance ima- The paired levator veli palatini muscle is the ging of a 4-year-old child with an enlarged adenoid most important muscle for normal velophar- pad (white arrow). yngeal closure.8 This muscle originates at the 86 SEMINARS IN SPEECH AND LANGUAGE/VOLUME 32, NUMBER 2 2011

Figure 3 Nasopharyngoscopy demonstrating the velum, lateral pharyngeal walls (LPW), posterior pharyngeal wall (PPW) in the open (left image) and closed position (right image). Note the upward and backward movement of the velum and the medial movement of the lateral pharyngeal walls.

base of the on each side, specifically the the levator veli palatini muscle from its origin petrous portion of the . Accord- to insertion (Fig. 5). ing to Huang et al,8 part of the muscle may The function of the levator veli palatini originate at the junction of the cartilaginous muscle is to retract and elevate the velum. As and bony parts of the auditory (eustachian) this muscle contracts during speech, it pulls the tube. The levator muscle bundles course ante- velum up at a 45-degree angle to close against riorly, medially, and inferiorly to insert into the the posterior pharyngeal wall. middle of the velum.9 As the muscle bundles enter the body of the velum, the bundles fan outward, becoming more massive in size and Musculus Uvulae joining with the opposing levator veli palatini The musculus uvulae, also called the ‘‘uvular muscle bundle. Fig. 4 demonstrates a computer muscle,’’ sits within the muscular sling created

reconstruction of the levator veli palatini by the levator muscle bundles (Fig. 4). It is Downloaded by: SASLHA. Copyrighted material. muscle bundles. As seen in this figure, the considered to be the only intrinsic muscle of the paired muscles are suspended from the base of velum. As such, the entire muscle in contained the skull and create a sling arrangement. This within the body of the velum, having no sling arrangement also can be observed from an external attachments. The musculus uvulae is MRI section that courses along the length of generally discussed as a single muscle; however,

Figure 4 Computer reconstructed model using magnetic resonance imaging to demonstrate the normal internal anatomy of the velopharyngeal mechanism from a lateral view (left) and a dorsal view (right). ANATOMY AND PHYSIOLOGY OF THE VELOPHARYNGEAL MECHANISM/PERRY 87

Figure 5 Midsagittal magnetic resonance imaging (MRI) of the velopharyngeal mechanism. The bottom right legend shows the axis in which the MRI was sampled. The top two arrows point to the levator veli palatini muscle origin at the base of the skull, and the bottom arrow shows the insertion in the velum. Note the sling arrangement to the muscle bundles. research has demonstrated that in some indi- the posterior pharyngeal wall during velophar- viduals there are two distinct muscle bundles.5 yngeal closure.11 By creating added bulk to the This is likely just a variation and whether a nasal surface of the velum and giving the velar person has a single muscle bundle or two has no ‘‘knee’’ (place where the velum bends) a convex

functional significance on the velopharyngeal configuration, this helps to ensure a tight Downloaded by: SASLHA. Copyrighted material. mechanism. The musculus uvulae fibers origi- velopharyngeal seal. nate from the palatal aponeurosis. The palatal aponeurosis is a thin, fibrous lamella (a fine, platelike structure) just behind the posterior Tensor Veli Palatini nasal spine. The palatal aponeurosis provides The tensor veli palatini is a thin, broad, flat support and stiffness to the velum and also acts muscle that originates at the scaphoid fossa at as a buffer between a highly moveable (velum) the base of the medial pterygoid plate of the and immoveable (hard palate) structure. The sphenoid bone and the lateral margins of the musculus uvulae courses posteriorly from its eustachian tube.12,13 The tensor veli palatini origin and continues along the nasal surface muscle has several muscle attachments and of the velum. The fibers are most cohesive near courses parallel to the levator muscle.13 The the middle of the velum and become more bulk of the muscle lies within the pterygoid diffuse as they reach the uvula proper.4,10 The fossa, which is the space between the lateral musculus uvulae is encapsulated by a connective and medial pterygoid plates. The muscle tissue sheath, which likely functions to provide courses medially and inferiorly and ends in support and stability to the muscle along its a tendon that winds around the hamulus of length.4 the medial pterygoid plate. The tendon con- The function of the musculus uvulae is to tinues medially into the body of the velum to assist in filling the gap between the velum and form the palatal aponeurosis, which is just 88 SEMINARS IN SPEECH AND LANGUAGE/VOLUME 32, NUMBER 2 2011

posterior to the posterior nasal spine of the continue vertically to insert into the lateral hard palate. pharyngeal walls and also onto the greater Although the course of the tensor veli horns of the of the . palatini muscle appears to be similar to that Due to the variations in the course of the of the levator veli palatini muscle, it has a muscle bundles, slightly different functions uniquely different function. It is generally have been associated with the bundles. The agreed that the primary function of this muscle upper transverse fibers (palatopharyngeus is to open the eustachian tube during swallow- proper) contribute to inward displacement of ing and yawning. Opening the eustachian tube the lateral pharyngeal walls and may also con- allows drainage of fluids in the middle and tribute to the formation of a Passavant’s ridge, also equalizes the air pressure across the ear- when present. The vertically oriented fibers drum.14 (palatothyroideus) facilitate in the overall posi- tioning of the velum.17–20 Although most literature supports the no- Superior Pharyngeal Constrictor tion that this muscle is more active during The superior pharyngeal constrictor is one of swallowing compared with speech, the palato- the three pharyngeal constrictor muscles (supe- thyroideus fibers appear to be in position to be rior, middle, and inferior pharyngeal constric- an antagonist to the levator muscle.17,18,21 The tors) that make up the length of the . transverse fibers may function to pull the lateral The superior pharyngeal constrictor is in the pharyngeal walls medially during velopharyng- region of the velopharynx and therefore is eal closure.16 The lateral and longitudinal na- functionally related to velopharyngeal closure. ture of the muscle might provide a narrowing This thin muscle has multiple origins, which effect on the pharynx, possible more important create distinct muscle bundles including pter- during swallowing. The function might also be ygopharyngeus, buccopharyngeus, mylophar- to elevate the pharynx or the larynx. Fig. 6 yngeus, and glossopharyngeus muscles. The demonstrates a dorsal view of the velopharynx muscle fibers form the upper lateral and poste- and how the vertical fibers of the palatophar- rior pharyngeal walls and meet posteriorly yngeus fibers are oriented relative to the pre- along the midline to form a , viously discussed muscles. which can be viewed along the dorsal surface of the pharynx. Some of the fibers have a direct

attachment to the velum and thus might assist Palatoglossus Downloaded by: SASLHA. Copyrighted material. in retraction of the velum.15 The horizontal The courses from the fibers might also contribute to the formation of lateral margins of the velum, through the a Passavant’s ridge, if present. The superior anterior faucial pillars, and inserts onto the constrictor muscle also can contribute to the lateral aspect of the tongue. The positioning velopharyngeal closure pattern, particularly if of this muscle is such that it is a direct antag- pharyngeal wall movement is observed (as in a onist to the levator veli palatini muscle and can circular closure pattern). serve to lower the velum. Elastic fibers within the anterior faucial pillar also may provide a passive restoration effect on the velum to help Palatopharyngeus lower the palate and open the velopharyngeal The is primarily a port for the production of nasal phonemes.22 vertically oriented muscle that is contained The muscle can also function to elevate the within the posterior faucial pillar. However, posterior tongue or to constrict the faucial this muscle does have a transverse component, isthmus. During swallowing, these actions as- as described by Cassel et al.16 The transverse sist the bolus by moving it posteriorly and fibers are referred to as the ‘‘palatopharyngeus inferiorly toward the esophagus. Muscle activ- proper’’ and course posteriorly from the velum ity during speech, however, is less consistent to terminate along the lateral pharyngeal walls. across individuals and speech sounds.17 Elec- The vertical fibers, called ‘‘palatothyroideus,’’ tromyography data have demonstrated that the ANATOMY AND PHYSIOLOGY OF THE VELOPHARYNGEAL MECHANISM/PERRY 89

Figure 6 Illustration of a dorsal view of the nasal surface of the velum and the major muscles of the velopharyngeal mechanism in an individual with normal anatomy. Note the following muscles: (A) levator veli palatini, (B) tensor veli palatini, (C) palatopharyngeus, (D) hamulus, (E) musculus uvulae, and (F) palatoglossus. Downloaded by: SASLHA. Copyrighted material. palatoglossus muscle is active during velar low- ius, which is near the orifice of the eustachian ering during speech for some but not all indi- tube in the nasopharynx.23 The fibers course viduals.22 This might be due to the variations in inferiorly through a fold of tissue called the the attachment of this muscle observed across ‘‘salpingopharyngeal fold’’ before terminating individuals with some individuals showing a in the lateral pharyngeal walls. The size and more posterior attachment on the velum com- presence of the muscle has been reported to be pared with others with an anterior velar attach- quite variable across individuals.24 For this ment. Collectively, contraction of the reason, it is unlikely that the muscle signifi- palatopharyngeus and palatoglossus muscles cantly impacts velopharyngeal closure in any in combination with velar elevation via the fashion; however, if present, the positioning of levator veli palatini muscle function conjunc- the muscle could provide a superior pull on the tively to provide velar positioning.17,18 lateral pharyngeal walls.

Salpingopharyngeus MOTOR AND SENSORY The salpingopharyngeus muscle is a small INNERVATIONS muscle that courses along the lateral pharyngeal Motor innervation for the velum is supplied walls. The muscle originates at the torus tubar- primarily through the trigeminal (cranial 90 SEMINARS IN SPEECH AND LANGUAGE/VOLUME 32, NUMBER 2 2011

nerve V) and the pharyngeal plexus of result, these muscles are forced to find an .25,26 In contrast, the tensor veli palatini alternative attachment site. The muscle that is muscle is innervated by the motor root of the most negatively affected by a cleft is the levator mandibular branch of the . veli palatini muscle. Instead of coursing Shimokawa et al25 observed through dissection through the velum and interdigitating in the and histology that the levator veli palatini midline of the velum, the muscle finds an muscle might also be innervated through the attachment onto the lateral and posterior aspect pharyngeal plexus and also through the lesser of the hard palate.30 Fig. 7 demonstrates this palatine nerve. It has also been suggested that abnormal muscle attachment in a computer- not all of the cranial nerves that supply the reconstructed model based on MRI data of an pharyngeal plexus are involved in motor inner- 8-month-old infant with a unilateral cleft lip vations for the velopharyngeal muscles.27 and palate before primary . Sensory innervation to the palatal and phar- A cleft of the velum may cause the muscu- yngeal mucosa is primarily through branches of lus uvulae to be reduced in size and located in cranial nerves V, VII, IX, and X.26 Muscle the hemivelar segments or to be absent. There is spindles are sensory receptors within a muscle. no research to confirm whether a repaired cleft They detect changes in muscle length and con- palate might result in any muscle fibers from the vey this information to the brain through the musculus uvulae to be active. Also observed in sensory neurons. Muscle spindles have been an unrepaired cleft palate is a lateral insertion of found in the tensor veli palatini, levator veli the tensor veli palatini onto the bony aspects of palatini, and palatoglossus muscles.28,29 They the cleft, including the maxillary tuber and have not been found in other velopharyngeal pterygoid process. Typically, primary palatal muscles.28 surgery does not aim to restore correct position- ing of this muscle, which may contribute to poor auditory tube function and decreased ven- CLEFT PALATE ANATOMY tilation of the middle ear cavity.12 The attach- When a child is born with a cleft of the palate, ment of the palatoglossus and palatopharyngeus there is an absence of midline tissue, thus muscles, like the levator muscle, is more anterior creating a cleft. As previously discussed, many and lateral along the hard palate in individuals of the velopharyngeal muscles have insertions with a cleft palate. The superior pharyngeal that are along these midline structures. As a constrictor muscle and salpingopharyngeus Downloaded by: SASLHA. Copyrighted material.

Figure 7 Computer reconstruction of an unrepaired unilateral cleft lip and palate in an 8-month-old infant (based on magnetic resonance imaging data). Note the attachment of the levator veli palatini muscle onto the hard palate (white arrows on right image). ANATOMY AND PHYSIOLOGY OF THE VELOPHARYNGEAL MECHANISM/PERRY 91 muscles are typically not affected or altered as a 4. Kuehn DP, Kahane JC. Histologic study of the result of the cleft palate. normal human adult soft palate. Cleft Palate J Aside from abnormal muscle positioning 1990;27(1):26–34; discussion 35 found in individuals with a cleft palate, other 5. Kuehn DP, Moon JB. Histologic study of intra- velar structures in normal human adult specimens. complications are present due to the existence Cleft Palate Craniofac J 2005;42(5):481–489 of a cleft in the palate. This causes the oral and 6. Finkelstein Y, Lerner MA, Ophir D, Nachmani A, nasal cavities to be coupled, leading to prob- Hauben DJ, Zohar Y. Nasopharyngeal profile and lems related to feeding, maxillary facial growth, velopharyngeal valve mechanism. Plast Reconstr dentition, middle ear function, hearing, and Surg 1993;92(4):603–614 speech. These are just a few of the obstacles 7. Witzel MA, Posnick JC. Patterns and location of these children and their families encounter velopharyngeal valving problems: atypical findings on video nasopharyngoscopy. Cleft Palate J 1989; throughout the child’s life. 26(1):63–67 8. Huang MH, Lee ST, Rajendran K. Anatomic basis of cleft palate and velopharyngeal surgery: CONCLUSIONS implications from a fresh cadaveric study. Plast Proper velopharyngeal closure depends on sev- Reconstr Surg 1998;101(3):613–627; discussion eral velopharyngeal muscles. During rest, the 628–629 velopharyngeal port is kept open to allow for 9. Boorman JG, Sommerlad BC. Levator palati and palatal dimples: their anatomy, relationship and breathing through the nasal cavity. During clinical significance. Br J Plast Surg 1985;38(3): speech, the velum elevates for oral productions 326–332 and is maintained in a fully elevated position 10. Azzam NA, Kuehn DP. The morphology of until it is lowered for nasal productions. The musculus uvulae. Cleft Palate J 1977;14(1):78–87 velum is also able to vary in the force of closure 11. Kuehn DP, Folkins JW, Cutting CB. Relation- depending on the speech sound. For example, ships between muscle activity and velar position. high vowels such as /i/ and /u/ use a greater Cleft Palate J 1982;19(1):25–35 12. Abe M, Murakami G, Noguchi M, Kitamura S, closure force compared with that of low vowels 5 Shimada K, Kohama GI. Variations in the tensor such as /a/ and /ae/. This rapid and precise veli palatini muscle with special reference to its control found among the structures related to origin and insertion. Cleft Palate Craniofac J velopharyngeal closure make this a particularly 2004;41(5):474–484 challenging area to investigate. Improving our 13. Barsoumian R, Kuehn DP, Moon JB, Canady JW. understanding of the anatomy and physiology An anatomic study of the tensor veli palatini and dilatator tubae muscles in relation to eustachian of the velopharyngeal mechanism can ultimately Downloaded by: SASLHA. Copyrighted material. tube and velar function. Cleft Palate Craniofac J result in a positive impact on the treatment of 1998;35(2):101–110 individuals with an abnormal mechanism, such 14. Leider J, Hamlet S, Schwan S. The effect of as those born with cleft palate. swallowing bolus and head position on eustachian tube function via sonotubometry. Otolaryngol Head Neck Surg 1993;109(1):66–70 REFERENCES 15. Kuehn DP. Velopharyngeal anatomy and physi- ology. Ear Throat J 1979;58(7):316–321 1. Moon JB, Kuehn DP. Anatomy and physiology of 16. Cassell MD, Moon JB, Elkadi H. Anatomy and normal and disordered velopharyngeal function for Physiology of the Velopharynx. Multidisciplinary speech. In: Bzoch KR ed. Communicative Dis- Management of Cleft Lip and Palate. Philadel- orders Related to Cleft Lip and Palate, 5th ed. phia, PA: Saunders; 1990 Austin, TX: Pro-Ed; 2004:67–98 17. Moon JB, Smith AE, Folkins JW, Lemke JH, 2. Kummer AW. Anatomy and physiology: the Gartlan M. Coordination of velopharyngeal orofacial structures and velopharyngeal valve. In: muscle activity during positioning of the soft Kummer AW ed. Cleft Palate and Craniofacial palate. Cleft Palate Craniofac J 1994;31(1): Anomalies: Effects on Speech and Resonance, 2nd 45–55 ed. Clifton Park, NY: Delmar Cengage; 2008:3–30 18. Seaver EJ III, Kuehn DP. A cineradiographic and 3. Ettema SL, Kuehn DP. A quantitative histologic electromyographic investigation of velar position- study of the normal human adult soft palate. ing in non-nasal speech. Cleft Palate J 1980;17(3): J Speech Hear Res 1994;37(2):303–313 216–226 92 SEMINARS IN SPEECH AND LANGUAGE/VOLUME 32, NUMBER 2 2011

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