I. Deglutition (Swallowing)

A. Overview

1. Complex process requiring coordination between normal anatomical structures.

2. Safe swallowing involves coordinated contraction of the pharynx, relaxation of the upper esophageal sphincter (UES), and protective movement of oropharyngeal structures (aerodigestive protection).

3. Encompasses three phases: oral, pharyngeal, and esophageal.

B. Phases of Deglutition

1. **Oral Phase (Voluntary)** a. Bolus is formed in the oral cavity. b. Mouth functions as both a sensory and motor organ. c. Physical changes in the food bolus occur, including changes in: i. Size ii. Shape iii. Volume iv. pH v. Temperature vi. Consistency

2. **Pharyngeal Phase (Reflexive / Complex)** a. Bolus is transported through the upper pharynx and into the esophagus by pharyngeal peristalsis. b. Approximately 1 second in healthy individuals. c. Steps:

• Tongue loads and transports the bolus posteriorly (especially with solid feedings). This action initiates the swallow reflex.
• Elevation of the pharyngeal tube with bolus delivery. This helps to direct the bolus and prepare the pathway.
• Velopharyngeal closure. This prevents nasal regurgitation by sealing off the nasal cavity from the pharynx.
• Relaxation of the Upper Esophageal Sphincter (UES). This allows the bolus to pass from the pharynx into the esophagus.
• Closure of the laryngeal vestibule, followed by a peristaltic wave in the posterior pharyngeal constrictors, propeling the bolus past the UES. This protects the airway (trachea) by closing it off and then using a muscular wave to efficiently move the bolus down.

3. **Esophageal Phase** a. Peristaltic contractions, bolus propelled through the distal esophagus to the stomach. b. The UES: i. Manometry reveals high-pressure zone (~3 cm in length). ii. Composed of striated muscle located just caudal to the hypopharynx. iii. Tonically closed at rest, opens during swallowing. iv. Resting pressure is variable (30-80 mm Hg). v. Main muscle is the cricopharyngeal muscle, innervated by vagal branches of the pharyngeal plexus. vi. Distention of the esophagus produces a reflex increase in UES resting pressure (protective). vii. Acidification of the esophagus may cause an increase in UES resting pressures.

C. Neurology of Deglutition

The neurology of deglutition, or swallowing, is a complex process influenced by sensory feedback and controlled by specific regions of the brain and cranial nerves. Firstly, all three phases of swallowing – oral, pharyngeal, and esophageal – are not simply pre-programmed actions. They are dynamically adjusted based on sensory information received from the mouth and throat. Touch and pressure receptors located throughout the oral and pharyngeal cavities send signals to the brain, providing information about the size, texture, and location of the food bolus. This sensory feedback allows the swallowing mechanism to adapt, ensuring safe and efficient bolus transport. This is particularly important for individuals with swallowing impairments (dysphagia) because modifying the sensory input (e.g., using thicker liquids or changing the bolus size) can improve swallowing function and reduce the risk of aspiration.

Secondly, the initiation of swallowing can be triggered by stimulating specific areas within the mouth and throat. These areas are innervated (supplied with nerves) by cranial nerve IX (the glossopharyngeal nerve) and the superior and recurrent laryngeal nerves, which are branches of the vagus nerve (cranial nerve X). When these regions are stimulated, it sends signals to the brainstem that initiate the swallow reflex, setting off the coordinated sequence of muscle contractions necessary for the pharyngeal phase.

Thirdly, while the initial decision to swallow is influenced by the cerebral cortex (the outer layer of the brain involved in conscious thought and voluntary movement), the pharyngeal and esophageal phases of swallowing do not require the cerebral cortex to function. The neurons responsible for coordinating these phases are located in the pons and medulla, which are lower brainstem structures. These areas contain the swallowing center, which controls the complex sequence of muscle contractions and relaxations necessary for safe and efficient bolus transport through the pharynx and esophagus. This is demonstrated by the fact that infants born with anencephaly, a condition in which they lack nervous tissue above the midbrain, can still exhibit swallowing reflexes, indicating that the essential neural circuitry for these phases resides in the brainstem.

D. Changes During Development

1. **Infants:** Tongue lies entirely within the oral cavity; the larynx is positioned high in the neck; the oropharynx is small in volume. 2. **Childhood:** The base of the tongue descends. 3. **Adulthood:** The larynx descends to the level of the seventh vertebra.

E. Sucking (Oromotor Phase of Feeding):

Sucking is the initial, and crucial, oromotor component of feeding, especially in infants. It's the process by which infants draw liquid (typically milk or formula) into their mouths. This process isn't just one thing; it's categorized into two main types: non-nutritive sucking and nutritive sucking.

1. Non-Nutritive Sucking (NNS)

• Definition: Non-nutritive sucking refers to sucking that doesn't primarily involve the ingestion of nutrients. It's often seen when an infant sucks on a pacifier, finger, or even when they're "dry sucking" without any milk flow.
• Characteristics:
• Faster Frequency, Shorter Duration: Non-nutritive sucking bursts typically have a higher frequency (more sucks per unit of time) and shorter durations compared to nutritive sucking. It's a quicker, less sustained pattern. Think of it as practice or comfort sucking.
• Not as much coordination: NNS requires less strength and coordination than nutritive sucking.
• Benefits in Preterm Infants (Important Detail): This is a key area. For premature infants, non-nutritive sucking during gavage feeding (where nutrition is delivered directly into the stomach via a tube) can have significant benefits:
• Improved Weight Gain: Multiple studies have shown that preterm infants who engage in NNS during gavage feeding tend to gain weight more efficiently. The mechanisms behind this are thought to be:
• More Efficient Nutrient Absorption: NNS may stimulate gut motility and enzyme production, leading to better digestion and absorption of nutrients from the gavage feed.
• Decreased Energy Requirements: NNS may have a calming effect on the infant, reducing restlessness and activity levels. This, in turn, lowers their overall energy expenditure, allowing more of the consumed calories to be directed towards growth. Additionally, it stimulates the release of hormones that support digestion and calmness.
• Faster Transition to Oral Feeding: NNS helps develop and strengthen the oral muscles required for oral feeding, therefore helping transition a preterm infant to oral feedings faster.
• Improved Oxygen Saturation: NNS can help infants practice breathing and swallowing coordination.
• Improved State Regulation: NNS can help infants regulate their state (wakefulness, sleepiness, etc.) and reduce stress.

2. Nutritive Sucking (NS)

• Definition: Nutritive sucking is sucking that does result in the ingestion of nutrients. It's the typical sucking pattern used when breastfeeding or bottle-feeding.
• Characteristics:
• Integrated and Synchronized Movements: Nutritive sucking requires a precise coordination of the lips, cheeks, tongue, and palate. The infant must create a seal around the nipple, generate negative pressure to draw milk out, and then coordinate swallowing and breathing. The infant's coordination must also match the rate of flow of the milk.
• Higher strength and endurance NS requires a lot of strength and endurance in the oral muscles in order to express milk and coordinate the suck-swallow-breathe pattern.
• Slower Frequency, Longer Bursts: NS has a slower rate, and consists of longer and more sustained suck swallow bursts.
• Development in Term Infants:
• Usually Fully Developed in Normal Term Infants: Typically, healthy, full-term infants possess the necessary oromotor skills and coordination for effective nutritive sucking. They are born with the reflexes and anatomical structures needed to feed successfully.

Important Additional Details to Know:

• Suck-Swallow-Breathe Coordination: A critical aspect of nutritive sucking is the coordination between sucking, swallowing, and breathing. Infants must be able to briefly interrupt their breathing to swallow, and then quickly resume breathing to maintain adequate oxygenation. Difficulties with this coordination can lead to aspiration (liquid entering the lungs).
• Assessment: Speech-language pathologists (SLPs) and other healthcare professionals often assess an infant's sucking skills as part of a feeding evaluation. This involves observing the infant's lip seal, tongue movement, coordination, and overall feeding efficiency.
• Intervention: If an infant exhibits difficulties with sucking, various interventions can be implemented, such as:
• Positioning changes
• Nipple modifications (flow rate, shape, etc.)
• Oral motor exercises

In summary, both non-nutritive and nutritive sucking play vital roles in infant development. NNS offers benefits like improved weight gain in preterm infants, while NS is the primary means of obtaining nutrition. Understanding the characteristics of each type of sucking is crucial for identifying and addressing potential feeding difficulties.

G. Etiologies of Disordered Deglutition (Dysphagia) in Children (see below)

1. Prematurity 2. Nasopharyngeal Disorders: Choanal atresia, nasal and sinus infection, tumor, septal deviation. 3. Oral and Oropharyngeal Disorders: Cleft lip/cleft palate, craniofacial syndromes (Treacher Collins, Pierre Robin Sequence). 4. Laryngeal Disorders: Stenosis, webs, clefts, paralysis, laryngomalacia. 5. Congenital Defects: Laryngotracheoesophageal cleft, congenital esophageal stenosis, TEF and/or esophageal atresia, esophageal web/stricture, vascular anomalies (double/right aortic arch). 6. Trauma to Upper Airway/Oropharynx 7. Neurologic Defects: Hypoxia, microcephaly, cortical atrophy, CNS infection, Chiari malformation, dysautonomia, sensory integration/processing disorders, CNS injury. 8. Neuromuscular Diseases: Myotonic muscular dystrophy, myasthenia gravis, poliomyelitis. 9. Muscular Disorders: Achalasia

Dysphagia – (Disordered Deglutition)

This section outlines the key aspects of dysphagia, including its symptoms, evaluation, potential causes, and diagnostic testing. Dysphagia, in general, refers to difficulty swallowing. It's a symptom, not a disease itself, and it can result from a wide range of underlying conditions.

A. Sensation of Difficulty Swallowing:

• This is the hallmark of dysphagia. Individuals often describe the feeling as food getting stuck in their throat or chest as it travels from the mouth to the stomach. The precise location of the sensation can provide clues about the phase of swallowing that is affected.

B. Three Phases of Deglutition and Associated Symptoms:

• As a reminder, normal swallowing is divided into oral, pharyngeal, and esophageal phases. Dysphagia can affect one or more of these phases, and the symptoms will vary accordingly.
1. Oral Phase Symptoms: This phase involves preparing the bolus (food) and moving it to the back of the mouth. Symptoms of oral phase dysphagia include:
• Drooling: Inability to control saliva in the mouth.
• Constantly Open Mouth: Difficulty maintaining lip closure.
• Poor Sucking: Weak or uncoordinated sucking (especially in infants).
• Refusal to Swallow: Actively rejecting food or liquid.
• Coughing, Gagging, Choking: These are protective reflexes triggered by food or liquid entering the airway (trachea) instead of the esophagus.
• Respiratory Distress: Signs of difficulty breathing (e.g., increased respiratory rate, nasal flaring, retractions) due to aspiration.
• Aspiration: Food or liquid entering the airway, which can lead to pneumonia and other respiratory complications.
2. Pharyngeal Phase Symptoms: This is a rapid, reflexive phase where the bolus is propelled through the pharynx (throat) and into the esophagus. Symptoms include:
• Difficulty Initiating a Swallow: Hesitation or delay in triggering the swallow reflex. This is a common symptom that should be investigated.
3. Esophageal Phase Symptoms: This phase involves peristalsis (coordinated muscle contractions) moving the bolus down the esophagus to the stomach. Symptoms include:
• Dysphagia After Swallowing: The sensation of food getting stuck in the chest or throat after the swallow has been initiated.

• Odynophagia: Painful swallowing. This often accompanies dysphagia, especially in cases of esophagitis (inflammation of the esophagus) or other esophageal disorders.

C. Historical Features in Evaluating Dysphagia:

Taking a detailed history is crucial for diagnosing dysphagia. Certain features can point to the underlying cause:

1. Drooling or Open-Mouth Posture: Suggests problems with oral phase control, muscle weakness, or structural abnormalities in the mouth.
2. Dysphagia During Swallowing: Indicates pharyngeal phase abnormalities. These can be due to:
• Anatomical abnormality (e.g., pharyngeal web, tumor).
• Oropharyngeal discoordination (problems with the timing and coordination of the muscles involved in swallowing).
• Neurologic disorder (affecting the nerves and muscles that control swallowing).
3. Dysphagia After Swallowing: Suggests esophageal abnormalities.
4. Dysphagia with Solids: Often points to structural or mucosal lesions in the esophagus (e.g., stricture, tumor, web).
5. Dysphagia with Solids and Liquids: More likely indicates a motility disorder (problem with the muscles of the esophagus), such as achalasia or esophageal spasm.
6. Feeding History: This is particularly important in infants and children.
• Length of Meal Times: Prolonged feeding times (e.g., more than 30 minutes) can be a sign of difficulty swallowing or fatigue.
• Stressful Meal Times: Stress and anxiety during feeding can worsen dysphagia symptoms.
• Signs of Respiratory Distress with Feeding: Coughing, choking, wheezing, or changes in breathing pattern during feeding.
• Poor Weight Gain and/or Weight Loss: This is a significant concern and indicates that the child is not getting adequate nutrition due to swallowing difficulties. A growth chart is essential to assess this.

D. Physical Examination:

A thorough physical exam helps identify potential causes of dysphagia.

1. Structure of the Face, Oral Cavity, and Oropharynx: Look for any obvious abnormalities, such as cleft lip/palate, tumors, or structural deformities.
2. Intact Hard and Soft Palate: Essential for proper oral phase function and velopharyngeal closure during the pharyngeal phase.
3. Tongue Midline, Normal Size, and Motility: The tongue plays a critical role in bolus formation and propulsion.
4. Size of the Mandible Normal: Rule out conditions like Robin sequence, which is characterized by a small mandible (micrognathia), glossoptosis (tongue falling back), and airway obstruction.
5. Control of Head, Neck, and Body Position Normal: Proper positioning is important for safe and efficient swallowing.
6. Gag Reflex: Its presence and strength are assessed. An absent, weak, or hyperactive gag reflex can indicate neurological issues. Note: The gag reflex is not always a reliable indicator of swallowing function. Some individuals with normal swallowing may have a weak or absent gag reflex, while others with dysphagia may have a strong gag reflex.
7. Feeding Trial: Observe the patient eating or drinking to assess swallowing function.
• Primitive Reflexes or Movements: Persistence of primitive reflexes (e.g., tongue thrust) can interfere with normal swallowing.
• Positions of Head, Neck, and Body During Swallowing: Observe for abnormal head posture or compensatory movements.
• Abnormal Feeding Behaviors: These can include tongue thrusting (pushing the tongue forward), food aversion, and refusing to open the mouth.
• Change in Voice Quality After Feeding: A wet or gurgly voice after swallowing can indicate aspiration.

E. Differential Diagnosis of Dysphagia:

This section lists potential causes of dysphagia, categorized by the phase of swallowing affected:

1. Oral Phase Dysphagia:
• Nasopharyngeal Disorders: Choanal atresia/stenosis (blockage of the nasal passages), sinus and nasal infections can interfere with normal breathing and swallowing coordination.
• Oral Cavity Abnormalities: Cleft lip/palate, hypopharyngeal webs/stenosis, craniofacial syndromes (e.g., Robin sequence), trauma, infection, mucositis (inflammation of the mouth), tonsillar/adenoid hypertrophy.
• Profound Developmental Delay: Can result in uncoordinated chewing and swallowing.
• Skeletal Muscle Hypotonia, Cranial Nerve Abnormalities: Can lead to spasticity, dystonia, or paresis (weakness).
2. Pharyngeal Phase Dysphagia:
• Anatomic Defects of the Pharynx: Pharyngeal webs cause obstruction and dysphagia.
• Anatomic Defects of the Larynx: Laryngeal stenosis, laryngopharyngeal cleft (abnormal opening between the larynx and pharynx), laryngeal web.
• Cricopharyngeal Dysfunction:
• Cricopharyngeal Achalasia: Failure of the cricopharyngeus muscle (part of the UES) to relax.
• Muscular Hyperplasia: Enlargement of the cricopharyngeus muscle.
• Cricopharyngeal Discoordination: Problems with the timing and coordination of the muscle.
• Central or Cranial Nerve Damage: Failure of the UES to relax.
• Neurologic Defects: Poor motor oropharyngeal coordination. CNS conditions (head trauma, brain injury, microcephaly, anencephaly, myelomeningocele, Chiari malformation, dysautonomia). Neuromuscular disorders (myotonic dystrophy, myasthenia gravis, Guillain-Barre syndrome, poliomyelitis, spinal muscular atrophy).
3. Esophageal Phase Dysphagia:
• Strictures: Caused by caustic ingestion, peptic esophagitis, eosinophilic esophagitis (EoE), epidermolysis bullosa, trauma, gastric rest (after surgery), pill esophagitis.
• Anatomic Abnormalities: Diverticulae (outpouchings of the esophageal wall), tracheoesophageal fistula (TEF), aberrant cervical thymus, webs.
• Disorders of Esophageal Motility:
• Achalasia:
• Abnormal or absent peristalsis.
• Failed or incomplete lower esophageal sphincter (LES) relaxation.
• Hypertensive LES (elevated pressure).
• Mechanism is impaired bolus transit. Stretching of esophageal wall stimulates nociceptors (pain receptors) that cause dysphagia.
• Diffuse or Distal Esophageal Spasm:
• Simultaneous esophageal contractions after >20% of swallows.
• LES relaxation is normal.
• Dysphagia caused by esophageal dilation proximal to the transient muscular obstruction.
• Treatment with Ca2+ channel blockers or anticholinergics.
• Nutcracker Esophagus:
• Very strong simultaneous esophageal body contractions.
• Odynophagia is the more prominent symptom.
• Systemic Neuromuscular Disorders: Can cause dysphagia.
• Vascular Anomalies: Compression of the esophagus.
• Dermatologic Disorders: Affect squamous epithelium of esophagus.
• Inflammation and Injury: All forms of esophagitis.

F. Testing for Dysphagia:

Several diagnostic tests can help evaluate dysphagia:

1. Videofluoroscopic Swallow Study (VFSS) or Modified Barium Swallow (MBS): Detects abnormalities in swallowing, aspiration, and esophageal obstruction (oral and pharyngeal phases).
2. Barium Swallow: Detects anatomic abnormalities in the esophagus (esophageal phase).
3. Laryngoscopy: Assesses possible upper airway malformations.
4. Upper Endoscopy: Evaluates mucosal disease in the esophagus (esophageal phase).
5. Impedance Probe: Detects both acid and nonacid gastroesophageal reflux.
6. Esophageal Manometry: Diagnoses motility disorders.

Key Takeaways:

• Dysphagia is a symptom that requires careful evaluation to determine the underlying cause.
• A thorough history and physical exam are essential for diagnosis.
• Various diagnostic tests can help identify abnormalities in swallowing function.
• Treatment depends on the underlying cause and may involve dietary modifications, swallowing therapy, medication, or surgery.
• Aspiration is a serious complication of dysphagia that can lead to pneumonia and other respiratory problems. Therefore, assessment is crucial.

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