Pathophysiology of Swallowing Impairments Part 2: Disordered Behaviors

Pathophysiology of Swallowing Impairments

Part 2: Disordered Behaviors

The Oral Preparatory Phase In general, when the oral preparatory phase of swallow is

disturbed, drooling and leakage of liquids are observed, as well as pocketing of more solid foods on the weaker side.

These behaviors reflect deficits in facial and tongue musculature.

Some specific disorders include: Reduced labial closure—food falls from the mouth

anteriorly; Reduced mandibular range of motion—difficulty putting

mandible into proper occlusion for chewing, especially in patients who have had lower jaw surgery; and

The Oral Preparatory Phase

Reduced buccal tension—food falls into the anterior or lateral sulcus as the patient is chewing.

When there is reduced range and/or coordination of tongue movement, difficulty may be exhibited in pulling food back together into a cohesive bolus.

Swallow may be initiated with food spread throughout the oral cavity.

Some specific problems may include: Reduced tongue movement laterally; and Reduced tongue elevation.

The Oral Phase

Problems with the oral phase affect lingual propulsion of the bolus through the oral cavity.

Some specific disorders include: Reduced tongue range/coordination—food is not

maintained cohesively for anterior to posterior lingual transport.

Disturbed lingual peristalsis—somewhat random, non-productive, disorganized motion.

The Oral Phase

Repetitive lingual rolling—repetitive upward and backward movement of the anterior tongue and failure of the posterior tongue to lower; bolus can only move to midpalate before it rolls forward again.

Reduced anterior to posterior tongue movement—the tongue moves minimally in posterior direction so food just sits on the tongue.

Reduced ability to shape the tongue—liquid or paste cannot be held in a cohesive bolus so material spreads throughout the oral cavity and may fall into the anterior lateral floor of the mouth during attempts at oral transit.

The Oral Phase

Tongue thrust—food is pushed up against the anterior teeth by forward protrusion of the tongue when the swallow is initiated.

Other oral phase problems include: Piecemeal deglutition--bolus is not swallowed in single,

cohesive mass; only a portion or piece of the bolus is swallowed at a time. Repeated swallows are necessary to clear the oral cavity;

Aspiration before the swallow—when unswallowed bolus or portion thereof falls into the open airway and makes its way into the pulmonary bronchi.

The Pharyngeal Phase

Disorders of the pharyngeal phase include dysfunctions of the swallow programming mechanism in the brainstem to organize and initiate the swallow response, or dysfunctions of any of the neuromuscular components that actualize the response behaviors.

Problems may be seen at the level of the velum, the pharynx, the larynx, and/or the PE segment.

At the level of the velum, observed problems may include: Reduced or inadequate velar elevation Material being refluxed through the nose.


Since velopharyngeal (VP) closure during swallow lasts only a second or less, as the bolus passes the VP port, nasal reflux occurring later in the swallow is a result of dysfunction farther down the pharynx.

If the bolus cannot pass through the pharynx into the esophagus, it may be refluxed upward into the nasopharynx when the VP port is normally open.

Reduced pharyngeal peristalsis results in a significant amount of food residue coating the pharyngeal walls after the swallow response has been triggered.

Common sites of pharyngeal residue include:


Bilateral or unilateral vallecular stasis Bilateral or unilateral pyriform sinus stasis

When residue is found in both the pyriform sinuses, the dysfunction is usually at the cricopharyngeus.

If residue in the pyriforms is combined with residue in other parts of the pharynx, it is a symptom of generalized pharyngeal dysfunction, and not an isolated cricopharyngeal problem.

With any location of pharyngeal stasis, the patient is at risk for aspiration of the material after swallow, when the airway is again open for breathing.


At the level of the larynx, reduced anterior movement and/or closure of the larynx can result in penetration.

When anterior movement is reduced, residual material may remain on top of the larynx after swallow.

Lack of anterior movement of the larynx may also prevent the cricopharyngeus from opening to permit passage of the bolus.

Lack of adequate laryngeal closure may permit material to fall to the level of the vocal folds.

If sensation is decreased, material may not be expectorated until farther down in the trachea.


Material may continue to trickle in to the bronchi and pulled into the lungs.

If the pharyngeal stage is not triggered by the time the bolus head reaches the point where the mandible crosses the tongue base, the pharyngeal swallow is said to be delayed.

However, in the elderly person, the swallow is often not initiated until the bolus reaches the valleculae or even the pyriform sinuses.


Abnormal pharyngeal swallow delay is often accompanied by struggle behavior to stimulate the swallow.

The tongue base may be moved forward and backward in an attempt to life the larynx.

In infants, pharyngeal triggering and delay time is quite different from that of adults.

The bolus may be collected in the valleculae before the pharyngeal swallow is triggered.

In an infant, an abnormal delay is defined as more than 1 second between the last tongue pump and the onset of the swallow, or aspiration occurring during bolus collection.


If the central pattern generator in the brainstem does not program the entire pharyngeal swallow to trigger, the bolus may fall to the pyriform sinuses, or into the unprotected open airway.

This is sometimes referred to as an absent swallow response.

The Esophageal Phase

The esophageal phase of swallowing may be affected by structural and/or motility changes in the esophagus.

Common structural disorders consist of stenosis, or narrowing of the esophageal lumen, luminal deformity, and diverticula.

Motility disorders affect the contraction amplitude, duration, and wave progression of esophageal peristalsis.

Part 3: Adult Etiologies

Neurological Disorders

Neurologic disorders affecting swallowing can be categorized in many different ways: by the anatomic site of the lesion, such as the central or

peripheral nervous system; by the pathologic process, such as ischemia or

degeneration; by the underlying etiology; or by the clinical presentation such as those accompanying

dementia and movement disorders.

Disorders of the CNS

Disorders of the CNS can be nondegenerative or degenerative.

Nondegenerative disorders of the CNS are outlined in Table 1 and include vascular, traumatic, neoplastic, congenital, and iatrogenic etiologies.

Based on clinical progression, degenerative disorders may be subclassified into progressive and relapsing disorders.

Progressive degenerative disorders may be further subclassified based on their salient clinical characteristic into dementias and movement disorders (see Table 2).

Table 1 Nondegenerative Disorders Affecting Swallow

Vascular Trauma Neoplastic Congenital Iatrogenic

Stroke Traumatic brain injury

Brain tumor Cerebral palsy Medication Induced

Surgery Induced

Tardive dyskinesia

Carotid endarterectomy

Cervical spine surgery

Table 2 Degenerative Disorders Affecting Swallow

Progressive Course Relapsing—Remitting Course

Dementia Movement Disorders Multiple sclerosis

Alzheimer’s disease Parkinson’s disease

Frontotemporal dementia

Progressive supranuclear palsy

Lewy body dementia Olivopontocerebellar atrophy

Vascular dementia Huntington’s disease

Wilson’s disease

Epidemiology of Dysphagia in CNS Disorders

The incidence of neurogenic dysphagia worldwide is 400,000 to 800,000 new cases per year.

The reported incidence of dysphagia in specific neurologic diseases is variable, owing in part to patient selection methods (e.g., consecutive patients, case series) and evaluation methods (e.g., questionnaire, clinical evaluation, diagnostic evaluation).

Determination of dysphagia based on patient complaint or clinical swallowing evaluation generally underestimates the incidence.

Table 3 summarizes dysphagia prevalence for specific neurological diseases.

Table 3. Prevalence of dysphagia for specific

neurologic diseases Disease Prevalence of dysphagia

Stroke 65% dysphagia in acute stroke (Daniels et al.)

Traumatic brain injury 25% (Winstein)–61% (Mackay et al.)

Cervical spine surgeryCarotid endarterectomy

50% (Smith-Hammond et al.)2.5% (AbuRahma & Lim)–42% (Ekberg et al.)

Alzheimer's dementia 32% (Volicer et al.)–84% (Horner et al.)

Frontotemporal dementia 30% (Ikeda et al.)

Parkinson's disease 50% (Lieberman et al.)–63% (Fuh et al.)

Progressive supranuclear palsy Initially: 16%, later stages: 83% (Litvan et al.)

Olivopontocerebellar atrophy 44% (Landis et al.)–75% (Schut)

Huntington's disease 85% (Edmonds)

Multiple sclerosis 34% (Calcagno et al.)

Amyotrophic lateral sclerosis 100% (Kawai et al.)

Non-Degenerative Disorders: Stroke

Stroke is the most common cause of neurogenic dysphagia.

When identified by VFSS, dysphagia is documented in approximately 65% of acute stroke patients, with the incidence of aspiration ranging from 43% to 58%.

Prevalence of dysphagia following stroke depends on when in the course of recovery the detection of a swallowing impairment was made: In patients with acute stroke--less than 5 days after onset--the

prevalence of dysphagia is as high as 50%; Two weeks after stroke the prevalence may be only 10% -

28%.

Stroke

Swallowing abnormalities in stroke are variable and may include: oral lateral sulci retention delayed oral transfer delayed elicitation of a pharyngeal swallow decreased hyolaryngeal elevation, and aspiration.

Non-Degenerative Disorders: TBI

Dysphagia following TBI is common and depends on the brain region involved.

Brain injury resulting from trauma is generally more diffuse than that following stroke, and cognitive impairments are often prominent depending on the site and severity of injury.

The secondary effects of head injury on cortical and respiratory function may necessitate tracheostomy with or without ventilation, which interfere with swallow ability.

Traumatic Brain Injury (TBI)

Patients who are semicomatose cannot concentrate or cooperate during attempts at feeding.

Prevalence data for patients who survive TBI and enter a rehabilitation setting vary.

Lazarus and Logemann (1987) found that approximately 45% of patients admitted to rehab during a nine-month period had signs of dysphagia.

Winstein (1983) found that 33% were dysphagic upon admission and that only 6% were dysphagic after five months of rehab.

Non-Degenerative Disorders: Brain Tumor

As with stroke and TBI, brain tumors may result in dysphagia depending on which brain region is involved.

Pathologically, brain tumors may be benign or malignant.However, their space-occupying nature can result in

significant neurologic dysfunction. Swallowing may be affected by infiltration of the tumor

into brain regions important in deglutition.

Brain Tumor

In addition, the treatment modalities for the tumor including surgery and radiation therapy may affect swallowing.

Unlike the dysphagia resulting from stroke or TBI, swallowing disorders secondary to a brain tumor may be progressive as the tumor invasion increases.

Iatrogenic—Medication Induced

Any drug capable of causing extrapyramidal side effects (EPS) and tardive dyskinesia (TD) is by definition a neuroleptic (Latin for “seize the neuron”).

EPS, especially TD, can occur in up to 20% of patients receiving neuroleptics.

Neurologic symptoms include repetitive movement of the lower face, lips, and tongue (orobuccolingual dyskinesia), and movement of the trunk and pelvis.

Neuroleptics are a class of drugs which includes anti-psychotics used for schizophrenia; anti-emetics; anti-spasmodics; and the prokinetic medications commonly used in gastroenterology (reglan, propulsid, zantac).

Iatrogenic—Medication Induced

Symptoms suggestive of EPS or isolated reports of movement disorders are associated with medications used to treat irritable bowel syndrome, ulcerative colitis, inflammatory bowel disease, and GERD.

These medications are capable of causing potentially permanent side effects which may range from dramatic and debilitating to very subtle.

Symptoms may be reversible if identified early and the medication changed to newer medications which do not produce these symptoms.

Iatrogenic--Surgery Induced

Surgery involving the neck, such as cervical spine surgery and carotid endarterectomy, may produce dysphagia generally owing to manipulation of cranial nerves.

The anterior approach to cervical spine surgery results in dysphagia and co-occurring postoperative dysphonia more frequently than a posterior approach due to retraction and stretch injury to the cranial nerves of the pharyngeal plexus.

Injury of the VII, X, and XII cranial nerves may occur with carotid endarterectomy, as these nerves are close to the carotid bifurcation.

Postoperative edema may also contribute to the dysphagia.

Progressive Degenerative: Dementia

Patients with dementia not only have problems with swallowing but also with feeding; limb apraxia may affect their ability to use eating utensils; visual agnosia may affect their ability to recognize and accept food.

Deficits in transfer of the bolus in the oral cavity are also prominent.

Because of the progressive nature of these disease processes, dysphagic symptoms can occur anywhere in the disease progression.

Some patients complain of dysphagia as the initial symptom of the disease; others may never complain of dysphagia.

In general, as disease severity increases, so does dysphagia.

Progressive Movement Disorders

Movement disorders constitute a group of degenerative metabolic disorders of the CNS involving the extrapyramidal and cerebellar pathways.

The characteristics of the disordered movement allow for their easy clinical recognition.

Such disorders include: Parkinson’s disease (PD) and its variants; progressive supranuclear palsy (PSP); amyotrophic lateral sclerosis (ALS); Huntington’s disease (HD); multiple sclerosis (MS); myasthenia gravis (MG).


Dysphagia occurs in about 50% of those individuals with PD.

The prevalence of dysphagia is probably higher in those patients with PD who also have significant dementia

Common dysphagic manifestations include:Abnormal lingual peristalsis;Reduced pharyngeal peristalsis;Delayed swallow response; andCP dysfunction.


Progressive supranuclear palsy (PSP) is a rare, generally sporadic, rapidly progressive disease involving the basal ganglia, frontal lobes, midbrain, and brainstem.

Onset typically occurs between the ages of 50 and 60 years.

Symptoms include vertical ophthalmoplegia, axial rigidity, pseudobulbar (upper motor neuron) palsy, and dementia.


The bulbar presentation of ALS includes dysarthria, dysphonia, dysphagia, sialorrhea, muscle atrophy, and fasciculations.

Approximately 25% of ALS patients will have bulbar-related symptoms at onset.

When ALS affects the bulbar (pontine) musculature, dysphagia may be one of the first symptoms of the disease.


In the early stages of ALS, oral phase problems are due to either a dysfunction in the transport of the bolus at the anterior part of the tongue, or in the holding of the bolus at the posterior part of the tongue (Kawai, Tsukuda, Mochimatsu, Enomoto, Kagesato, Hirose, Kuroiwa, & Suzuki, 2003).

Aspiration is more often associated with impaired holding function (oral containment) at the posterior part of the tongue, than to transport dysfunction.

There is almost no delay in swallowing at the pharyngeal level, nor problems with esophageal peristalsis.


Similar to ALS, not all patients with MS will be dysphagic unless bulbar musculature is involved.

Because of the disease’s tendency to produce ataxic symptoms, the coordination of deglutition and breathing may predispose these patients to dysphagia, as well as to oral and pharyngeal muscle weakness and incoordination.

Hartelius and Svensson (1994) found that more than 33% of patients with MS had either chewing or swallowing problems.

Other common dysphagic manifestations include aspiration: before the swallow due to reduced lingual control;


before the swallow due to a delayed swallow response; during the swallow due to reduced laryngeal closure; after the swallow due to reduced pharyngeal peristalsis; and after the swallow due to CP dysfunction.

In selected populations of patients with MG, approximately one third are dysphagic.

The prevalence of dysphagia largely depends on the extent of muscle fatigue.


A recent study by Dolton-Hudson, Koopman, Moosa, Smith, Bach and Nicolle (2002) found that 45% of their participants with MS had oral preparatory phase dysphagia, 65% had oral phase dysphagia, and 100% had pharyngeal phase dysphagia.

Specific oral preparatory phase problems included poor bolus formation and extended chewing with reduced buccal tension leading to spillage of material into the lateral sulci.


Oral phase problems included slow bolus transports, piecemeal deglutition, and poor retro-oral seal of the tongue and palate, leading to residue on the tongue base and soft palate.

Pharyngeal phase dysphagia included delayed swallow response and reduced tongue base retraction toward the pharyngeal wall, resulting in residue in the valleculae and pyriform sinuses.

Aspiration occurred in about 1/3 of the patients, with the majority aspirating during the swallow.

Systemic Rheumatic Diseases

Systemic rheumatic diseases, such as dermatomyositis, polymyositis, rheumatoid arthritis, scleroderma, and Sjogren’s syndrome are rarer than PD or MS, but deserve consideration in a discussion of dysphagia and neurologic disease.

Dermatomyositis and polymyositis are characterized by inflammation of the proximal skeletal muscles.

Thus muscles of the pharynx are often affected but the smooth muscles of the esophagus are spared.


On VFSS, there is usually prominence of the CP muscle, decreased epiglottic tilt, and moderate to severe pharyngeal residue (Murray & Carrau, 2001).

About 67% of patients with myositis have demonstrable delayed transit through the cervical esophagus.

Rheumatoid arthritis (RA) is a chronic relapsing inflammatory arthritis, usually affecting multiple diarthrodial joints.

Women are more commonly affected than men, with a ratio of 3:1.


RA is associated with xerostomia, TMJ syndrome, cervical spine arthritic disease, and decreased peristaltic amplitude in the proximal esophagus, all contributing to swallowing problems.

Rheumatic laryngeal involvement may result in cricoarytenoid joint fixation, affecting laryngeal closure.

A study by Ekberg, Redlund-Johnell, and Sjoblom (1987) found that 65% of patients with RA had pharyngeal dysfunction.


Scleroderma is a disorder characterized by progressive fibrosis and vascular changes.

As many as 90% of patients with scleroderma have complaints related to swallowing.

Dysphagia is first noticed while swallowing solids due to poor motility through the inferior 2/3 of the esophagus.

Secondary effects on the oral and pharyngeal stages have been reported.


Sjogren’s syndrome (SS) is an autoimmune disorder that produces dryness of the eyes, nose, and mouth.

Xerostomia, oral pain, glossodynia, and dysgeusia are prominent features of SS.

As many as 75% of patients diagnosed with SS have dysphagia, which has the potential to involve all stages of swallowing function.

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Pathophysiology of Swallowing Impairments Part 2: Disordered Behaviors