Swallowing Disorders

Swallowing can be thought of as an interplay between two separate but related, physiologic events, airway protection - will a patient be able to prevent themselves from choking while eating - and bolus transport - how food moves from the mouth into the stomach.

All swallowing disorders can be traced to some malfunction of one or both of these events. The diagnostic tests and therapeutic maneuvers that take place at the Voice and Swallowing Center address the issues of airway protection and bolus transport.

But first, what is difficulty with swallowing, or DYSPHAGIA? Dysphagia is defined as any subjective or objective patient complaint of trouble swallowing, coughing, choking or inability to safely handle food or secretions.

Neurologic Swallowing Disorders

A) Stroke

Dysphagia is very common following acute stroke, reported as frequently as 50% and one of the most common reasons for someone to have a swallowing evaluation (1, 2, 3 ) 31, 32, 33). Dysphagia can result from either unilateral or bilateral strokes (4, 5 ) 22, 23). While the majority of cortical, or supratentorial, strokes that result in swallowing difficulties typically resolve in approximately two weeks, patients who have persistent dysphagia after the first two weeks are at high risk for consequences of dysphagia such as aspiration penumonia (6, 7, 8, 9) 38, 93, 94, 95).

Brainstem, or infratentorial, strokes, as opposed to cortical, or supratentorial, strokes, are typically associated with more persistent and serious problems with dysphagia (10, 11). (26, 27). The brainstem contains neural pathways essential to the involuntary control (pharyngeal and esophageal phases) of swallowing. Because of interconnections between the right and left sides of the brainstem, unilateral brainstem strokes can result in bilateral laryngopharyngeal motor and sensory dysfunction (10, 11). Precisely because of the combined motor and sensory deficits that can result after stroke, a swallowing test that specifically examines both the motor and sensory components of the swallow, such as FEESST, is particularly useful in assisting patients with swallowing difficulty after stroke.

B) Parkinson's Disease

Parkinson's disease is characterized by bradykinesia, or slowing of motor movement, intention tremor and rigidity. It is a chronic, progressive disease with dysphagia very common with the oral and pharyngeal stages of swallowing altered (12) 90). Laryngopharyngeal sensation can also be affected in patients with Parkinson's who have swallowing difficulty.

The physical exam signs strongly suggestive of Parkinson's disease are tongue tremor, impaired pharyngeal peristalsis, or movement, and delayed opening of the cricopharyngeus muscle (13, 14) 91, 92). Parkinson's disease is primarily a disorder of the basal ganglia. It is due to an imbalance between dopamine-activated and acetylcholine-activated neural pathways in the corpus callosum. Treatment of Parkinson's involves dopamine replacement medications.

C) Mental retardation, developmental delay, cerebral palsy

Institutionalized, profoundly mentally retarded individuals, many with underlying seizure disorders or on psychotropic medications, are at very high risk from complications due to swallowing disorders. Mortality is most often due to respiratory infections.
In developmentally delayed individuals, there are several abnormalities in the swallowing mechanism such as prolonged oral preparatory and oral phases of swallowing; tongue dysfunction; delay in triggering of the swallow reflex; and, pharyngeal residue post-swallow. Delay in triggering the swallow reflex increases the risk of aspiration, since the glottis remains open until the swallow is completed, and food material may trickle into the laryngopharynx prematurely.

Mental retardation combined with cerebral palsy aggravates dysphagia by adding cognitive impairment to poor oral motor control. Therapy in this population must take into account the limited or ability of these patients to cooperate with therapeutic techniques (15) (86).

D) Myopathies (Muscular dystrophies)

Muscle diseases are likely to cause swallowing disorders. Dysphagia occurs with high incidence in oculopharyngeal dystrophy, mitochondrial myopathies, and polymyositis. It has also been identified in Duchenne myopathy. Detection of, and attention to, dysphagia is important because of the risk of asphyxia from choking (16) (88). Myopathy-related dysphagia is capable of affecting all stages of swallowing. One can see weak pharyngeal peristalsis and impaired laryngeal elevation. Patients typically swallow repeatedly to clear a food bolus from the pharynx; often nasal regurgitation or choking ensues (17) (89).

Management options are limited. Only polymyositis and inclusion body myositis respond to medical therapy, the former responding to corticosteroids (17). Gastrostomy and cricopharyngeal myotomy are the surgical options available. Indications for gastrostomy in patients who cannot consume adequate nutrition orally are more defined than those for cricopharyngeal myotomy. Upper esophageal sphincter (UES) hypertension does not seem to be the predominant problem; therefore, the usefulness of a cricopharyngeal myotomy is probably indirect in assisting weak neck and pharyngeal muscles to pull open a more compliant UES. Cricopharyngeal myotomy is considered to be contraindicated when pharyngeal propulsion is severely compromised (16, 17).

E) Amyotrophic Lateral Scelrosis (ALS or Lou Gehrig's Disease)

ALS is a progressive neuromuscular disease affecting both upper and lower motor neurons. The disease is characterized by both bulbar and spinal symptoms and physical findings. While the rate of progression of symptoms is extremely variable and unpredictable among patients with the disease, bulbar ALS usually follows a recognizable, progressive course.

It is the bulbar symptoms which are most distressing since they affect the functions of speech, swallowing and breathing, including protection of the lower airway. Denervation results in muscle atrophy, and it is deterioration in respiratory muscle function, i.e., diaphragm and accessory muscles of breathing, that most often causes death from pneumonitis and respiratory failure (18, 19, 20) (75, 76, 77).

Bulbar ALS tends to progress predictably through four muscle groups. First, the tongue and lips are affected. Second, muscles of the palate, mastication, pharyngeal constrictors and buccinators. Third, the upper facial muscles, sternocleidomastoid and vocal cords. Fourth, the extraocular muscles are affected. Deterioration of the respiratory muscles can occur at anytime and at any rate during the course of the disease.

Physical findings seen early on in ALS (first muscle group) include dysarthria, tongue fasciculations, saliva drooling from the mouth, and inability to whistle.

Dysfunction of the second muscle group results in palatal and masticatory dysfunction. There is reduced palatal elevation when the gag reflex is stimulated. Early findings of weakness of the masticatory muscles are subtle, but in more advanced disease muscles antagonistic to the muscles of mastication pull the jaw downward, resulting in the mouth remaining open and leading to drooling and drying of the lips, oral cavity and oral secretions.

Deterioration of upper facial nerve branches follows involvement of the lower face (third muscle group). The sternocleidomastoid and trapezius are variably affected, but when they are, there may be difficulty in holding the head upright and in shrugging the shoulders. Vocal fold dysfunction probably affects both adduction and abduction, but the effect on abduction is more noticeable. Phonation is usually preserved, even in advanced disease; however, absence of stridor is probably more related to weakness of the respiratory muscles than to the narrowed glottis.
Extraocular muscles (group four) are infrequently involved, and when they are, the disease is far-advanced and the patient usually ventilator-dependent.

Dysphagia symptoms range from essentially normal eating habits to complete inability to swallow. Solid food dysphagia occurs first, closely followed by aspiration of thin liquids. Tucking the chin down toward the chest while swallowing tends to shelter the laryngeal inlet under the tongue base, thereby reducing the likelihood of aspiration. At some point, eating becomes such a chore because of aspiration, food spillage and prolonged mealtimes, that tube feeding should be considered. While a variety of options are available, a percutaneous gastrostomy (or jejunostomy, for patients with reflux) performed under local anesthesia and sedation is preferable in most cases.

F) Geriatric

As one ages various changes in swallowing physiology take place involving the oral, pharyngeal and esophageal stages of swallowing. With increasing age, tongue mobility diminishes (21) (78) partially as a result of loss of tongue muscle fiber (22) (79) and partially due to an increase in the amount of connective tissue in the tongue (23) (80). In addition to alterations in motor function, sensory discrimination in the tongue diminishes with increasing age (24) (81).

With increasing age, laryngo-hyoid elevation is delayed (25) (82). This finding, combined with the neuromuscular changes in the tongue, will lead to spillage of material into the valleculae and pyriform sinuses. In addition, with increasing age it has been found that individuals have a delay in the initiation of a swallow, a decrease in the duration of the pharyngeal phase of swallowing and a decrease in the duration of cricopharyngeal opening (26) (83). In addition to these alterations in primary motor functions, there is neuro-histologic data as well as clinical data that clearly demonstrate a diminution in laryngeal and hypopharyngeal sensitivity with increasing age (27, 28) (84, 85). The overall effect of these alterations in oropharyngeal and laryngopharyngeal physiology is an increased risk for aspiration as one ages (15, 25) (82, 86).

Infectious and Inflammatory Swallowing Disorders

A) Bacterial

There are numerous bacterial sources of infection in the head and neck that can result in dysphagia. The most common is bacterial tonsillitis and pharyngitis. While typically there is an associated odynophagia, physical examination of the oral cavity and laryngopharynx will reveal erythema, edema and sometimes an exudate. In the acute setting, treatment usually requires antibiotic therapy, however, in select situations, tonsillectomy may be the correct treatment option (29) (96).

Dental infections, when not aggressively managed can result in significant dysphagia, at times progressing to an airway emergency. The best example is a patient with swelling of the soft tissues of the floor of the mouth secondary to a purulent fluid collection resulting in elevation of the floor of mouth and tongue causing dysphagia as well as airway obstruction. This disease entity is also known as Ludwig's angina (30)(97). The treatment, in addition to high dose antibiotic therapy, is surgical drainage of the floor of mouth collection and, often, temporary tracheostomy.

Poorly treated, or insufficiently treated tonsil and pharynx infections can present with dysphagia secondary to purulent fluid collection in the parapharyngeal space of the neck. The parapharyngeal space is a potential space in the neck bounded superiorly by the skull base, inferiorly by the hyoid bone, laterally by the pterygomandibular raphe and medially by the lateral pharyngeal wall. The dysphagia from a parapharyngeal space infection is the result of displacement of the lateral pharyngeal wall medially over the hypopharynx (31) (98). Physical exam is remarkable for effacement of the angle of the mandible on physical examination of the neck, as well as medial displacement of the lateral pharyngeal wall on endoscopic examination of the laryngopharynx. Again, airway compromise is a potential complication of parapharyngeal space infections. Treatment, in addition to appropriate antibiotic coverage, is wide surgical drainage.

B) Viral

Viral infections of the oral cavity and laryngopharynx can cause dysphagia directly from lesions along the mucosal lining of the upper aerodigestive tract, or indirectly secondary to cranial nerve damage as a consequence of viral infiltration of upper cranial nerve ganglia. Herpes virus can cause both of these general categories of dysphagia. Herpes infections of the hypopharynx and larynx result in extremely painful mucosal lesions that precipitate dysphagia secondary to intense odynophagia (32) (101). In these cases systemic antiviral therapy might be indicated.
Patients with Ramsay Hunt syndrome, or herpetic viral infection of the external auditory canal, can develop significant cranial nerve neuropathy not only involving the facial nerve, but the glossopharyngeal, vagus and hypoglossal nerves as well (33) (102). In such instances systemic antiviral therapy is indicated as well as aggressive supportive measures such as dietary supplementation and airway protection (34) (103).

C) Fungal

Fungal infections of the oral cavity, pharynx and esophagus can result in significant dysphagia and odynophagia. While fungal infections such as those caused by Candida are typically seen in immunocompromised hosts, immune-competent individuals may develop candidiasis as well (35) (99). Physical examination is notable for a white, plaque-like exudate, sometimes with ulceration, on any mucosal surface from the wet line of the lips to the distal esophagus. Treatment ranges from topical antifungal therapy to systemic antifungal therapy, depending on the host immune status (36) 100).

D) Acid Reflux

Neoplastic

A) Benign

Swallowing disorders due to benign neoplasms are more common in infants and children than in adults. Benign neoplasms affecting the oral cavity and pharynx in children are primarily lymphangiomas and hemangiomas. They may occupy and disfigure multiple contiguous anatomic structures (e.g., tongue, floor of mouth, face and neck) and cause not only dysphagia but also airway obstruction.

Generally, congenital hemangiomas tend to regress and involute with age; in contrast, lymphangiomas do not spontaneously regress and, in fact, may grow and become more extensively infiltrative and obstructive as the child matures. Resection of these latter tumors is difficult and often carried out in stages, with every attempt made to preserve the integrity and function of normal structures.

In adults, benign masses such as lipomas and goiters may, depending on their size and location, cause dysphagia. Their diagnosis is relatively straightforward, and the decision to excise the mass is usually based on clinical presentation and symptoms.

Other benign tumors such as paragangliomas may cause dysphagia by impairing cranial nerve sensory and motor functions, either by their presence (compression, traction, stretching) or as a result of their treatment. Some surgeons advocate anticipation and correction of expected neurologic deficits (e.g., medialization thyroplasty for vocal cord paralysis) at the time of the tumor resection (37, 38) (37) (105).

B) Malignant

Dysphagia may result from both the malignancy itself (solid tumor, leukemia, or lymphoma) and/or the treatment of the malignancy (surgery, radiation, chemotherapy). Malignant neoplasms of the oral cavity or pharynx can cause dysphagia by virtue of the tumor mass itself, tissue fixation, local inflammation and pain (39) (106). Any adult with odynophagia (pain during swallowing) persisting for more than a few weeks deserves a careful examination to rule out malignancy. The symptoms may be very subtle, often described as a "slight irritation" or a sensation of "something down there", and may be dismissed as insignificant unless a reasonable index of suspicion is maintained.

Nonetheless, additional qualifiers such as unilaterality, referred otalgia, discomfort or irritation worse with swallowing, or gradual weight loss mandate a thorough inspection and palpation of all mucosal surfaces within the upper aerodigestive tract to exclude malignancy. Depending on the location and extent of a malignant tumor, dysphagia and/or odynophagia may be an early or late symptom of the disease. Primary tumors arising in the tongue base and supraglottic larynx are often "silent", not causing any symptoms until enlarged cervical nodes appear.

Patients rarely regain totally normal swallowing function after surgical resection of oropharyngeal or laryngeal malignancies. The magnitude of their dysphagia depends on the site of the primary tumor; extent of the surgical resection, structures involved in the surgical resection and type of reconstruction performed (40) (107). Defects in the roof of the mouth or laterally in the oral cavity are more easily compensated for with prostheses or static tissue flaps than are reconstructive efforts to replace the dynamic actions of the tongue or pharynx with their complex sensory and motor functions. Although the ideal goal in post-resection reconstruction is to duplicate the form and function of the excised tissues, matching their dynamic, functional and sensate properties is extremely challenging (41) (108).

Medications
Dysphagia can occur secondary to the use of tranquilizers implemented to control disruptive or aggressive behavior in the elderly demented population. Dysphagia induced by neuroleptics is uncommon but important to recognize because of its usual reversibility. Nonetheless, resolution of neuroleptic-induced dysphagia may take several months after discontinuation of the drug.

Neuroleptics, though considered equally efficacious in comparable doses, vary in potency and adverse side effects. For example, low potency chlorpromazine has a low incidence of extrapyramidal side effects (notably Parkinsonism) but often causes orthostatic hypotension, sedation and xerostomia (dry mouth). High potency haloperidol, on the other hand, has fewer anticholinergic side effects but is more likely to cause extrapyramidal side effects.

In addition to xerostomia, which can interfere with the oral preparatory phase of swallowing by reducing saliva production, neuroleptic-induced Parkinsonism causes morbidity through the rigidity and bradykinesia is exerts on the oral and pharyngeal phases of swallowing (42) (111). Specifically, oral phase impairments include repetitive tongue pumping, lingual tremor and prolonged oral transit time.

Effects on the pharyngeal phase include delayed initiation of the swallow reflex, inadequate post-swallow pharyngeal clearance, silent aspiration, prolonged pharyngeal transit time, incomplete laryngeal sphincter closure and cricopharyngeal dysfunction.

Xerostomia, which may precipitate dysphagia complaints, may also result from administration of anticholinergics, antihypertensives, cardiovascular agents, diuretics, opiates, antipsychotics, antiemetics, antidepressants, muscle relaxants and antihistamines (43) (112).

Trauma

A) Burns (thermal, caustic, laser)

Thermal, electrical, and laser energy and corrosive chemicals can cause circumferential stenosis of the oral cavity, pharynx, larynx and esophagus (44) (113). These stricture-causing injuries are usually severe, impairing alimentation, breathing, airway protection and phonation (45) (114).

B) Cervical spine surgery

Dysphagia is a recognized potential complication of anterior cervical spine surgery and it is usually transient, resolving within a few weeks, but it may be protracted or even permanent and require more extensive diagnostic and therapeutic intervention (46, 47, 48) (115-117). Studies utilizing videofluoroscopic swallow study, laryngeal videostroboscopy and EMG of patients with new-onset dysphagia after anterior approach to the cervical spine reveal a number of possible contributing factors: prevertebral soft tissue swelling at the surgical site; impaired upper esophageal sphincter (UES) opening; impaired oral or oral preparatory phases of swallowing; weak or absent pharyngeal clearance with associated aspiration (48, 49) (117, 118).

The surgical approach to C2-C3 is usually above the cranial nerve that moves the tongue, via an incision from the mastoid tip to the hyoid. Operations on the upper cervical vertebrae are associated with a higher incidence of disorders involving the oral and oral preparatory phases of swallowing. Approaches to C4-C7 require retraction of the carotid sheath and accompanying cranial nerves posterolaterally and retraction of the aerodigestive tract and larynx medially. At the higher levels (C3-C4) the superior laryngeal nerve and the hypoglossal nerve are at risk; at lower levels (C5-C7) the recurrent nerve is more vulnerable to injury. Right-sided anterior approaches to the cervical spine -- preferred by right-handed surgeons -- are associated with a higher incidence of inferior laryngeal nerve injury than left-sided incisions (50) (119). Cadaver dissections provide a likely explanation: there is less "slack" in the right inferior laryngeal nerve; hence, self-retaining retractors used to provide exposure to the cervical vertebrae are more prone to cause stretch injury to this structure.

Dysphagia and aspiration following anterior cervical spine surgery is common, underdiagnosed, and not well understood. Initial studies concentrated on injury to laryngeal innervation. More recent work confirms that edema at the operative site and injury to cranial nerves IX, X and XII contribute to these adverse outcomes. However, a more important and pervasive explanation may be denervation of the pharynx, i.e., disruption of connections between nerves of the pharyngeal plexus and the pharyngeal muscle fibers they innervate (47). Blunt dissection of tissue planes and retraction of neck structures to provide operative exposure may well be the basic underlying mechanism for dysphagia, with injury to specific cranial nerves or their more distal branches adding anatomic and physiologic specificity to the complication.

Diverticula
Hypopharyngeal diverticulum, also known as Zenker's diverticulum, was first described by Ludlow in 1764. It is a posterior herniation of hypopharyngeal mucosa most commonly through Killian's triangle just proximal to the cricopharyngeus muscle, a component of the inferior pharyngeal constrictor.

Cricopharyngeal dysfunction, suspected but as yet not proven to be the cause of diverticulum formation, is assumed to be etiologic; hence, cricopharyngeal myotomy is uniformly accepted as necessary for successful surgical treatment of Zenker's diverticulum (51) (120).

Psychogenic
As more information regarding etiologies of dysphagia are obtained, true psychogenic dysphagia is becoming less and less a reality. For example, the entity known as "globus hystericus", when studied more closely can range in etiology from site-specific posterior laryngeal swelling due to acid reflux injury (104) to esophageal motility disorders (52, 53) (104, 121). Therefore, the search for an organic etiology of dysphagia should be exhausted before ascribing a diagnosis of psychogenic dysphagia.