Natasha Mirza

Dysphagia is defined as difficulty in transporting food from the oral cavity to the esophagus. It is to be differentiated from odynophagia, which is painful swallowing. Dysphagia leads to high morbidity, mortality, and cost. It is very common in the chronic care setting and is seen in more than half of all patients who reside in nursing homes. Consequences of dysphagia involve poor nutrition and weight loss and also aspiration, which can lead to pneumonia. It is important to investigate the cause of dysphagia to rule out malignancy and nutrition and improve an individual’s quality of life. Detailed examination of the anatomy and physiology of each stage of deglutition is necessary to effectively diagnose and treat dysphagia.

Anatomy and Physiology

Normal swallowing is a complex cascade of events involving many levels of the central nervous system and voluntary and involuntary muscles in the head and neck. The neural control is in the motor nuclei of cranial nerves V, VII, IX, X, and XII. There are three phases of swallowing, each involving a particular subset of anatomical structures and muscle activity. These phases are the (1) oral phase, (2) pharyngeal phase, and (3) esophageal phase. The following structures are involved in the oropharyngeal aspect of swallowing:

Lips

Dentition and muscles of mastication

Tongue with both intrinsic and extrinsic muscles

Palate

Salivary glands, including the parotids and submandibular and sublingual glands

Pharyngeal muscles consisting of the superior, middle, and inferior constrictor muscles

Mechanism of Swallowing

Oral Phase

Preparatory stage: The first steps involve biting, lip closure, chewing (jaw motion and tongue movement), lubrication, and some digestion by saliva. The larynx and pharynx are at rest during this phase. The airway is open and nasal breathing continues until the voluntary swallow is initiated.

Oral stage: A bolus of suitable size and consistency is created and then transferred posteriorly from the oral cavity to the pharynx.

Pharyngeal Phase

The pharyngeal phase of swallowing is involuntary and under reflex control. Normally during this transit through the pharynx the bolus does not hesitate and a smooth movement is observed. It consists of two periods: (1) the early nasopharyngeal and oropharyngeal protective period whereby the bolus is prevented from regurgitating back into the oral cavity and (2) the later laryngeal protective period. This consists of laryngeal elevation, the folding backward of the epiglottis, and the activation of the laryngeal sphincters, including the adduction of the true vocal cords followed by adduction of the false cords and the aryepiglottic folds. The bolus is thereby diverted into the lateral piriform recesses. At rest the cricoid lamina touches the posterior pharyngeal wall at the level of the cricopharyngeal region. This position of the cricoid maintains closure of the upper esophageal sphincter (UES). As the larynx elevates and moves anteriorly during the swallow, extrinsic stretch is placed on the cricopharyngeus muscle and its adjacent fibers. The bolus is now cleared by the stripping action of the superior, middle, and inferior constrictor muscles. There is resetting of the larynx, and the upper esophagus now opens by the relaxation of the cricopharyngeus muscle.

Esophageal Phase

This phase involves active peristalsis or sequential contraction from top to bottom in two waves, primary peristalsis and secondary peristalsis. The esophageal phase is under involuntary neural control. At the base of the esophagus the lower esophageal sphincter (LES) is a circular muscular valve that opens to allow the passage of food but is otherwise closed to prevent gastroesophageal reflux.

Clinical Presentations of Dysphagia

Manifestations include poor oral control of food and saliva and present as drooling, speech disorders, nasal regurgitation, coughing, and choking spells with aspiration pneumonia and weight loss.