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).

References
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