------------------------------------------------------------------------------- TITLE: SWALLOWING PHYSIOLOGY SOURCE: Dept. of Otolaryngology, UTMB, Grand Rounds DATE: October 27, 1993 RESIDENT PHYSICIAN: John K. Yoo, MD FACULTY: Byron J. Bailey, MD, FACS DATABASE ADMINISTRATOR: Melinda McCracken, M.S. -------------------------------------------------------------------------------- "This material was prepared by resident physicians in partial fulfillment of educational requirements established for the Postgraduate Training Program of the UTMB Department of Otolaryngology/Head and Neck Surgery and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of members of the UTMB faculty and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion." I)Introduction Swallowing is a complex neuromuscular activity involving rapid coordination of structures in the oral cavity, pharynx, larynx, and esophagus. These structures must also support the physiologies of respiration, phonation, and articulation, in addition to deglutition. In normal adults, respiration ceases during the process of deglutition since the food bolus crosses the pathway that air takes on its way to the lungs. Normal swallowing can be divided into four stages: 1. Oral preparation 2. Oral 3. Pharyngeal 4. Esophageal The first two stages are under voluntary control, whereas the second two stages are involuntary, being under reflexive control. 1. Cortical control of swallowing is in the anterolateral cortex. Fibers descend through the internal capsule to the substantia nigra and then to the mesencephalic reticular formation. 2. The brainstem "swallowing center" is thought to be in the medulla between the posterior pole of the facial nucleus and the rostral pole of the inferior olive. Abnormal swallowing can produce a myriad of symptoms: 1. Subjective complaints of difficulty swallowing a. Dysphagia for solids suggests anatomic or obstructive etiology b. Dysphagia for liquids suggests neuromuscular etiology 2. Slow oral intake 3. Weight loss 4. Habitual throat clearing and "Postnasal drip" 5. Coughing 6. Rhinorrhea and sneezing accompanying meals 7. Wheezing/Bronchitis/"Asthma" 8. Pulmonary infections II) Oral Preparation A) Purpose: 1.Reduce solid food mechanically and mix with saliva to produce a pulverized consistency appropriate for swallowing 2.Produce the pleasurable sensation of eating B) Neuromuscular actions: 1.Lip closure to hold food in the mouth anteriorly 2.Tension in the labial and buccal musculature to close the anterior and lateral sulci 3.Rotary motion of the jaw for chewing 4.Lateral rolling motion of the tongue to position food on the teeth during mastication 5.Bulging forward of the soft palate to seal the oral cavity posteriorly and widen the nasal airway C) The most important neuromuscular action of this stage is the tongue motion since it is so extensively involved in the manipulation and mastication of food, as well as the formation of the food into a cohesive ball at the end of this stage. It does so by cradling the bolus by central depression and lateral elevation, positioning it against the palate in a cohesive mass. III) Oral Stage A) Purpose: 1. Move food from the front of the oral cavity to the anterior faucial arches, where the reflexive swallow is initiated B) Neuromuscular actions: 1. Tongue makes vertical contact anteriorly with alveolar ridge 2. Vertical tongue-to-palate contact progresses posteriorly, propelling the the bolus ahead of it toward the pharynx C) As in oral preparative stage, tongue motion is most important. Requires fine muscular control of tongue to elevate and move in a smooth anterior to posterior direction. Lasts less than one second in duration. IV) Pharyngeal Stage A) Purpose: 1. Transport food from the faucial arches to the esophagus 2. Protect the airway from aspiration B) Neuromuscular actions: 1. Velopharyngeal closure to prevent entry of food or liquid into the nasal cavity by: a. velar elevation by levator veli palatini and tensor veli palatini b. velar retraction by palatopharyngeus muscle c. anterior movement of posterior pharyngeal wall by superior pharyngeal constrictor-Passavant's pad d. medial movement of lateral pharyngeal walls (superior constrictor) 2. Pharyngeal peristalsis to propel bolus through pharynx and clear food residue from the pharyngeal recesses such as the valleculae and pyriform sinuses. Begins after tongue base retraction which drives the bolus at first. Bolus then pushed through pharynx by sequential contraction of the superior, middle, and inferior constrictors. 3. Airway protection to prevent aspiration through elevation and closure of larynx: a. larynx closes at three different levels during swallowing to prevent aspiration. True vocal cords close first, followed by the false vocal folds, followed by the approximation of the aryepiglottic folds and the coverage of the superior laryngeal inlet by the epiglottis. b. hyoid is suspended in the neck by the suprahyoid muscles (ant. digastric, mylohyoid, geniohyoid anteriorly; stylohyoid and post. digastric posteriorly). Larynx suspended in neck by muscle(thyrohyoid) and ligaments attached to hyoid. Hyolaryngeal complex elevated and moved forward during this stage. These actions tuck the larynx under the tongue and floor of mouth, up and out of the way of the passage of the food bolus. c. anterior, forward movement of hyolaryngeal complex most important in preventing aspiration, followed in importance by glottic closure. 4. Opening of the cricopharyngeal region to allow bolus passage into the esophagus. Upper esophageal sphincter(UES) made up o f cricopharyngeus attached to cricoid cartilage. At rest, UES closed to prevent air intake into the esophagus during breathing and to prevent reflux from the esophagus into the pharynx. Exact timing or triggering mechanism unknown, but several factors contribute to opening of UES: a. relaxation of UES to ENABLE opening b. upward, forward movement of larynx which is believed to be most important in opening the cricopharyngeal sphincter. c. bolus pressure increases the width of UES opening 5. tongue base retraction over bolus and pharyngeal contraction also aid in propulsion of food through the pharynx C) Lasts less than one second V) Esophageal stage A. Purpose: 1. To transport the food bolus from the UES to the stomach B. Anatomy: 1. Extends from level of cricoid cartilage(C6) to the cardia of the stomach with average length of 25 cm in males and 23 cm in females. 2. Physiologically and radiographically, 5 areas of constriction: a. cricopharyngeal narrowing b. hiatal narrowing c. thoracic inlet(T1) at the end of the cervical esophagus where foreign bodies lodge d. aortic arch which passes posteriorly(T4) e. bifurcation of the trachea where the left mainstem passes anteriorly(T6) 3. Most esophageal pathology encountered at these 5 areas C. Neuromuscular actions: 1. During the esophageal stage, there is the generation of the "primary wave" with the a force of 100 cm water pressure which moves the bolus the length of the esophagus 2. "Secondary wave" can be generated when there is increased pressure in mid-esophagus as occurs with residual food left in the esophagus after the completion of the "primary wave" 3. "Tertiary wave" may occur in the elderly and in certain pathologic states. Occurs in the distal esophagus and makes a non-progressive, corkscrew-like motion 4. UES opens with only 25 cm water pressure from above, but greater than 100 cm water pressure is needed to open it from below. LES opens with 5-7 cm water pressure from above, but greater than 25 cm water pressure required to cause reflux. D. Esophageal stage lasts 8-20 seconds VI) Bolus Characteristics' effects on swallowing A. Airway closure duration and cricopharyngeal opening duration increases with increasing bolus volume and viscosity B. Lingual palatal pressure and pharyngeal intra-bolus pressure increases with increasing bolus viscosity C. Oropharyngeal transit time increases with increasing bolus volume and viscosity D. Oral and pharyngeal stages occur almost simultaneously with increasing bolus volumes (>10mL) VII) Age effects on swallowing A. Infants: 1. Suckle feeding: multiple tongue-pumping of small amounts of liquid from nipple which collects in posterior oral cavity and valleculae before pharyngeal swallow occurs B. Elderly (>60 years of age) 1. Slight increase in time required to trigger reflexive swallow (0.4 sec) 2. Oral transit time and cricopharyngeal opening time slightly prolonged 3. No documented increase in aspiration frequency or residual bolus VIII) Disorders of deglutition A. Disorders of Mastication 1. reduced range of tongue motion 2. reduced buccal tension/buccal scarring 3. poor maxillary/mandibular alignment 4. poor dentition/mandibular defects 5. disorders involved in muscles of mastication B. Disorders of Preparatory Stage 1. reduced labial closure 2. reduced tongue movement to form or hold food bolus 3. abnormal hold position of the bolus 4. reduced oral sensitivity C. Disorders of Oral Stage 1. tongue thrust 2. reduced/disorganized anterior to posterior tongue movement 3. altered tongue contour 4. reduced ability to seal tongue to palate laterally 5. reduced tongue elevation 6. reduced buccaltension D. Disorders of Pharyngeal Stage 1. delayed or absent swallow reflex 2. inadequate velopharyngeal closure 3. reduced pharyngeal peristalsis 4. unilateral pharyngeal paralysis 5. cervical osteophyte 6. scarring of base of tongue/pharyngeal wall 7. cricopharyngeal dysfunction 8. reduced laryngeal closure 9. reduced laryngeal elevation 10. posterior cricoid webs E. Disorders of Esophageal Stage (Cervical) 1. lax cricopharyngeus 2. reduced esophageal peristalsis 3. diverticulum 4. esophageal obstruction 5. tracheo-esophageal fistula 6. extrinsic compression F. Disorders of Esophageal Stage (Thoracic) 1. Motor disorders a. achalasia b. globus hystericus c. diffuse esophageal spasm d. scleroderma 2. Inflammatory disorders a. gastro-esophageal reflux b. candida/herpetic esophagitis c. radiation esophagitis d. mucocutaneous diseases 3. Tumors a. benign (less than 10%) leiomyomata most common b. malignant (more than 90%) squamous cell constitute > 90% adenocarcinoma (e.g. Barrett's esophagus) less likely 4. Other esophageal pathology a. diverticula b. lower esophageal ring (Schatski) c. hiatal hernia d. perforation e. foreign bodies f. extrinsic compression IX) Aspiration A. Aspiration Before Swallow 1. poor tongue control 2. delayed or absent swallow reflex B. Aspiration During Swallow 1. sphincteric failure at the larynx C. Aspiration After Swallow 1. reduced laryngeal elevation 2. reduced pharyngeal peristalsis 3. unilateral pharyngeal paralysis 4. cricopharyngeal dysfunction X) Evaluation Techniques A. Bedside clinical examination 1. History a. when did disorder begin? b. worsen suddenly or gradually? c. how does problem vary with consistency of food? d. what specifically happens during swallow? e. does food get stuck along the way and if so, where? f. cough or choke? g. if residual food collects, where? 2. Examination of oral anatomy a. lip configuration b. palatal configuration (height and width) c. soft palate and uvular dimensions d. tongue size, shape, and mobility e. intra-oral scarring 3. Examination of function a. oral motor control b. labial control i. alternate /i/ with /u/ ii. rapidly repeating /pa/ iii.maintenance of tight lip closure with head position changes and jaw movement c. lingual control i. anterior: repeat /ta/ ii. extend and retract tongue iii.touch the corners of the mouth iv. touch sulci v. posterior: repeat /ka/ d. palatal/pharyngeal function i. repeat /a/ ii. levator and palatopharyngeus (elevation and retraction) iii.palatal reflex iv. gag reflex e. laryngeal function i. voice quality ii. repeat /ha/ iii.strength of cough and throat clearing to evaluate ability to clear aspirated material 4. Examination of swallow a. place hand with thumb lateral and fingers on the midline of anterior neck; place index finger in submental area; place long finger over hyoid area; place ring finger over thyroid cartilage; place small finger over cricoid cartilage; b. comparing time elapsed between tongue movement and hyolarnygeal movement gives a rough estimate of oral transit time c. gives no information of pharyngeal stage 5. Therapeutic positioning a. eliminate vallecular space by tilting head backwards after taking a bite to drain material from the mouth i. used for tongue motility disorders with normal pharyngeal/laryngeal function b. widen vallecular space by tilting head forwards i. used in patients with delayed triggering of swallowing reflex; collection in valleculae will rest long enough to facilitate triggering ii.used in patients with inadequate laryngeal closure, affords greater protection of airway by overhanging epiglottis c. unilateral pharyngeal paralysis i. turn head toward affected side to close the pyriform sinus on affected side directing the food bolus down the more functional side d. unilateral lingual paresis i. tilt head to stronger side ii.gravity aids to direct bolus to functional side B. Videofluoroscopy ("cookie swallow"; "modified barium swallow") 1. Standard method of evaluating the dynamic and rapid process of swallowing 2. Performed by radiologist and speech therapist in collaboration 3. Patient given small amount of contrast (Esophatrast) mixed with different consistencies(liquid, paste, solid); because only small amounts of material ingested, risk of sequelae from aspiration very low 4. Standard procedure performed in two views: a. Lateral plane with the fluoroscopy tube focused on lips anteriorly, pharynx posteriorly, soft palate superiorly, vertebra of C7 inferiorly; allows complete assessment of oral and pharyngeal motility, as well as presence of aspiration in pharyngeal stage of swallow b. A-P plane to assess any asymmetries in function particularly in vocal folds, as well as to view collection of bolus residue in vallecula and pyriform sinuses 5. Purposes of modified barium swallow: a. detect presence of and timing of aspiration b. define oropharyngeal motility disorders during swallows c. determine exact motility disorder responsible for aspiration, so that therapy can be initiated d. assess speed of the swallow (oropharyngeal transit times) e. evaluate cricopharyngeal function 6. If swallowing abnormality is seen in radiographic suite, various therapeutic maneuvers such as change in bolus texture, head position, and breathing are used to attempt to correct the abnormality 7. Disadvantages: a. poor detail with structural lesions b. some patient cooperation required c. esophageal phase not adequately studied C. Standard Barium Swallow ("upper GI" procedure) 1. Standard method of evaluating the esophageal stage (anatomy and motility) of swallows 2. Large amount of barium given; as a result, risk of sequelae from aspiration high 3. Procedure performed with the patient in a supine position in the anteroposterior view to minimize effect of gravity 4. Advantages: a. structural lesions well visualized b. esophageal stage studied c. gastro-esophageal reflux may be visualized 5. Disadvantages: a. large bolus can be aspirated b. oropharyngeal stages not studied c. no therapeutic manipulations possible D. Manometry 1. Intraluminal pressure measurments aid in identifying neuromuscular pathology 2. Pt swallows a soft tube containing pressure-sensitive gauges that can register pressures in the pharynx, cricopharyngeus, body of esophagus, and LES 3. Allows observation of pharyngeal peristalsis, opening of UES, esophageal peristalsis, and opening of LES 4. Manometry gives no information regarding amount or etiology of aspiration or on the functioning in the oral cavity or larynx 5. Newer techniques allow videofluoroscopy to be recorded simultaneously with manometry to allow precise spatial-temporal relationship between bolus motion and pressure changes to be observed E. Ultrasonography 1. Used to assess anatomy and physiology of the tongue during swallowing 2. Advantages: a. evaluate tongue motility b. no ionizing radiation c. quick, bedside examination 3. Disadvantages: a. limited to only the oral stage of deglutition F. Electromyography 1. Used to study oral musculature activity during deglutition 2. Difficult to study pharyngeal muscles involved in swallowing because positioning of electrodes difficult and frequently become dislodged during swallowing G. Fiberoptic endoscopy 1. Less widely used 2. Flexible endoscope can be used to evaluate swallowing dysfunction by observing the pharynx while patient's swallowing function is challenged with various food materials 3. Quick, bedside technique H. Endoscopy under anesthesia XI) Management A. Oral vs. Non-oral Feeding 1. Time needed to swallow a bolus (10 seconds) 2. Amount of aspiration (10%) 3. If swallow > 10 seconds in duration and aspirate >10% of each swallow, use non-oral feeding: a. NG tube b. pharyngostomy c. esophagostomy d. gastrostomy B. Direct vs. Indirect Therapy 1. Direct therapy: introduce food into the patient's mouth and attempt to reinforce appropriate behaviors during swallowing 2. Indirect therapy: use exercises to improve motor controls that are prerequisites for normal swallowing 3. If aspirate > 10%, use indirect therapy 4. If aspirate < 10%, use direct therapy C. Techniques to improve swallowing 1. Surgical reduction of osteophytes 2. Teflon injection (or temporary substance) into the reconstructed or damaged vocal fold 3. Dilatation of cricopharyngeus(UES) 4. Cricopharyngeal myotomy XII) Post-Operative Swallowing A. Rehabilitation requires: 1. Exact understanding of resection 2. Exact understanding of reconstruction B. Partial tongue resection 1. Less than 50% of tongue resected with primary closure: a. temporary swallowing disorder b. responds to range of tongue-motion exercises c. resolves 3-4 weeks post-op 2. More than 50% tongue resection: a. difficulty controlling material in the mouth and propelling bolus to pharynx b. treated by using a thinned paste or liquid managed by tilting the head back and allowing qravity to carry material into pharynx, range of tongue-motion exercises, and intra-oral maxillary prosthesis C. Anterior floor of mouth resection 1. If tongue not used in reconstruction a. few functional changes after surgery 2. If tongue used in reconstruction a. severe difficulty with lingual control of bolus, lingual peristalsis, mastication, ability to cup/hold bolus b. oral transit times no tongue < tongue flap < lingual-labial closures c. treated by using thinned paste or liquids, placing food posteriorly, tilting head back, and range of tongue exercises(for tongue flap patients only) D. Lateral floor of mouth resection 1. Potential difficulty with oral and pharyngeal stages of swallowing, especially if faucial arches resected 2. Prolonged oral transit times due to impaired lingual propulsion of bolus and collection of residual material in sulci 3. Delayed triggering of swallow reflex 4. Reduced pharyngeal peristalsis causing residual bolus to remain in the pharynx 5. Therapy: a. improve range of tongue-motion b. improve triggering of swallow reflex c. promote voluntary protection and clearing of airway d. cricopharyngeal myotomy may be necessary e. maxillary reshaping prosthesis E. Supraglottic laryngectomy 1. Removes upper two sphincters which provide airway protection a. aryepiglottic folds and epiglottis b. false vocal folds 2. If laryngectomy extends into base of tongue, most patients do well if resection is less than 1 cm of base of tongue; if > 1 cm, have problems with oral preparative/oral stages of swallowing 3. In reconstruction, usually: a. elevate remaining larynx and tuck under tongue for additional protection during swallow b. perform cricopharyngeal myotomy 4. Supraglottic swallow: a. occlude the TVC's by holding the breath b. swallow c. cough before inhaling F. Vertical laryngectomy 1. Few difficulties with deglutition after "typical hemilaryngectomy" because there is tissue bulk on the operated side against which the normal side can achieve normal laryngeal closure during swallowing 2. If arytenoid cartilage taken on operated side, then less likely to swallow normally with no aspiration 3. Therapy includes tilting head forwards to widen vallecular space, and thereby add to protection of airway by overhanging epiglottis G. Total laryngectomy 1. No risk of aspiration due to physical separation of gastro-intestinal tract from respiratory tract 2. Two problems: a. Scar tissue band at the base of tongue i. vertical closure line? ii. wound breakdown from tension? b. More extensive resection of pharyngeal mucosa producing tighter closure; some patients develop strictures in hypopharynx/esophagus XIII) Swallowing Dysfunction After Radiation Therapy A. Tissue response to radiation 1. Decreased salivary flow 2. Edema 3. Mucositis B. Treatment 1. Fluoride treatment to prevent caries 2. Costanzi's solution 3. Mycolex troches 4. Tincture of time C. Two most frequent disorders 1. Delayed swallow reflex 2. Reduced pharyngeal peristalsis XIV) Neuromuscular Swallowing Disorders A. Improvement anticipated 1. Stroke 2. Head trauma 3. Neurosurgical procedures 4. Poliomyelitis 5. Dysautonomia 6. Cerebral palsy B. Progressive degeneration anticipated 1. Parkinson's disease 2. Amyotrophic lateral sclerosis 3. Multiple sclerosis 4. Myasthenia gravis 5. Muscular dystrophy 6. Dystonia 7. Dermatomyositis --------------------------------------------------------------------------- SWALLOWING PHYSIOLOGY John K. Yoo, MD Byron J. 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