11.1 Dysphagia Assessment & Management

Overview of Swallowing Physiology

Swallowing (deglutition) is a complex neuromuscular process involving the coordinated activity of over 30 muscles and 6 cranial nerves (CN V, VII, IX, X, XI, XII). It is classically divided into four distinct phases: oral preparatory, oral transport, pharyngeal, and esophageal. Understanding the exact mechanical sequence and neuroanatomical control of each phase is essential for PM&R physicians diagnosing and managing neurogenic dysphagia following stroke, traumatic brain injury (TBI), spinal cord injury (SCI), motor neuron disease, and Parkinson's disease.

Oral Preparatory Phase

The oral preparatory phase is voluntary and variable in duration depending on bolus consistency and mastication requirements. Key mechanical actions include:

• Lip closure and labial seal: Maintained primarily by the orbicularis oris muscle (CN VII) to prevent anterior loss of food or liquid.
• Mastication: Involves the muscles of mastication (masseter, temporalis, medial and lateral pterygoids, innervated by CN V3) working in concert with cheek tension (buccinator, CN VII) to keep the bolus between the occlusal surfaces of the teeth.
• Bolus manipulation and containment: The tongue (CN XII) manipulates the food, mixing it with saliva secreted by the submandibular/sublingual glands (CN VII) and parotid gland (CN IX). Posteriorly, the soft palate (velum) is pulled down against the tongue base by the palatoglossus muscle (CN X) to form a posterior oral seal, keeping the bolus within the oral cavity and preventing premature spillage into the pharynx prior to swallow initiation.

Oral Transport Phase

The oral transport phase is also voluntary and lasts approximately 1 to 1.5 seconds.

• The tip and anterior margins of the tongue press against the alveolar ridge while the central tongue dorsum sequentially elevates from anterior to posterior in a stripping motion ("tongue pump").
• This action propels the cohesive bolus backward through the faucial arches into the oropharynx.
• The phase concludes as the bolus head passes the anterior faucial pillars (palatoglossal arches) or the posterior tongue base, which triggers the involuntary pharyngeal swallow reflex mediated by sensory afferents of CN IX (glossopharyngeal) and CN X (vagus) sending signals to the nucleus tractus solitarius (NTS) in the medulla.

Pharyngeal Phase

The pharyngeal phase is involuntary, highly rapid (lasting approximately 1 second), and critical for airway protection. The central pattern generator in the brainstem coordinates a rapid, automated sequence of events:

1. Velopharyngeal closure: The soft palate elevates and retracts against the posterior pharyngeal wall (levator veli palatini, CN X) to seal the nasopharynx and prevent nasopharyngeal regurgitation.
2. Hyolaryngeal elevation and anterior displacement: Suprahyoid muscles (mylohyoid [CN V3], geniohyoid [C1 via CN XII], anterior belly of digastric [CN V3], and stylohyoid [CN VII]) pull the hyoid bone and larynx superiorly and anteriorly. This mechanical traction physically pulls open the upper esophageal sphincter (UES) and tilts the epiglottis posteriorly.
3. Airway closure (Three Levels of Protection):
   • Level 1: True vocal fold adduction (lateral cricoarytenoid, interarytenoid muscles, innervated by the recurrent laryngeal nerve of CN X).
   • Level 2: False vocal fold (ventricular fold) adduction and arytenoid tilting forward to contact the base of the epiglottis.
   • Level 3: Epiglottic inversion over the laryngeal vestibule to divert the bolus laterally around the airway into the pyriform sinuses.
4. Pharyngeal constriction: The superior, middle, and inferior pharyngeal constrictor muscles (CN IX, X) contract sequentially in a top-to-bottom peristaltic wave, clearing the bolus through the pharynx.
5. Upper Esophageal Sphincter (UES) relaxation: The UES, primarily formed by the cricopharyngeus muscle (CN X), relaxes from its baseline tonic contraction. Combined with hyolaryngeal anterior traction and bolus pressure, the UES opens to allow the bolus to enter the esophagus.

Esophageal Phase

The esophageal phase is involuntary and lasts between 8 to 20 seconds. The bolus is propelled through the esophagus into the stomach by primary peristaltic waves. The proximal one-third of the esophagus consists of striated muscle (innervated by CN X via recurrent laryngeal nerve), the middle third transitions to smooth muscle, and the distal third is entirely smooth muscle (innervated by CN X via autonomous enteric plexus). The lower esophageal sphincter (LES) relaxes to allow bolus entry into the stomach.

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Diagnostic Instrumental Evaluations: VFSS vs. FEES

Clinical bedside swallow examinations (CSE) are valuable initial screening tools but suffer from high false-negative rates for detecting silent aspiration (aspiration without a reflexive cough). Therefore, objective instrumental evaluation is the gold standard for diagnosing dysphagia, defining underlying biomechanical deficits, and testing therapeutic interventions.

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Rosenbek Penetration-Aspiration Scale (PAS)

The Penetration-Aspiration Scale (PAS) is an 8-point validated ordinal scale used during instrumental swallowing studies to quantify the severity of airway invasion and the patient's physiological response to that invasion.

Clinical Pearl: A score of PAS 8 (Silent Aspiration) carries the highest clinical risk for aspiration pneumonia because sensory deficits prevent protective coughing, frequently seen in acute stroke, advanced neurodegenerative disease, or brainstem lesions affecting the sensory inputs of CN IX and CN X.

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Diet Texture Modification: The IDDSI Framework

The International Dysphagia Diet Standardisation Initiative (IDDSI) provides standardized terminology and testing methods for texture-modified foods and thickened liquids (Levels 0–7).

• Drink Levels (Levels 0–4):

  • Level 0 (Thin): Flows like water; passes through a 10 mL syringe in 10 seconds leaving 0 mL.
  • Level 1 (Slightly Thick): Thicker than water; leaves 1 to 4 mL in a 10 mL syringe after 10 seconds.
  • Level 2 (Mildly Thick): Flows off a spoon; leaves 4 to 8 mL in a 10 mL syringe after 10 seconds.
  • Level 3 (Moderately Thick / Liquidised): Can be drunk from a cup or spoon; leaves $>8$ mL in syringe.
  • Level 4 (Extremely Thick / Pureed): Cannot be drunk from a cup; eaten with a spoon; holds shape on a spoon.

• Food Levels (Levels 3–7):

  • Level 3 (Liquidised): Smooth texture, no bite size required.
  • Level 4 (Pureed): Smooth, uniform, no chewing required; does not require biting.
  • Level 5 (Minced & Moist): Soft and moist; small particle size ($\le 4$ mm for adults).
  • Level 6 (Soft & Bite-Sized): Soft, tender, bite-sized pieces ($\le 1.5$ cm for adults).
  • Level 7 (Regular / Easy to Chew): Normal, everyday foods; soft textures without hard/crunchy components.

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Compensatory Postures and Therapeutic Maneuvers

1. Chin-Tuck Maneuver (Head Flexion):
   • Mechanism: Flexes the neck forward, bringing the chin toward the chest. This narrows the pharyngeal airway entrance, shifts the epiglottis and tongue base posteriorly, and widens the vallecular space.
   • Clinical Indication: Ideal for patients with delayed pharyngeal swallow initiation, reduced tongue base retraction, or reduced airway closure resulting in premature spillage and pre-swallow aspiration.
2. Head Rotation (Turn to Impaired Side):
   • Mechanism: Rotating the head toward the weak/paretic pharyngeal side closes off the paretic pyriform sinus and directs the bolus down the intact, stronger contralateral pharyngeal side.
   • Clinical Indication: Unilateral pharyngeal weakness (e.g., Wallenberg syndrome / lateral medullary stroke).
3. Head Tilt (Tilt to Unimpaired Side):
   • Mechanism: Tilting the head toward the stronger side utilizes gravity to channel the bolus down the intact oral and pharyngeal side.
4. Effortful Swallow:
   • Mechanism: Asking the patient to "swallow hard" with all muscles. Increases tongue base retraction and pharyngeal pressure generation to clear pharyngeal residue.
5. Mendelsohn Maneuver:
   • Mechanism: The patient manually holds the larynx at its highest point of elevation for 2–3 seconds during the swallow. Prolongs UES opening and enhances hyolaryngeal excursion.
6. Supraglottic & Super-Supraglottic Swallow:
   • Mechanism: Patient holds breath, swallows, then immediately coughs. Super-supraglottic adds bearing down (Valsalva). Closes vocal folds prior to and during the swallow to prevent intra-swallow aspiration.