The mechanism of dysphagia
Swallowing mechanism
While eating and drinking, most people swallow more than a 1000 times a day. Swallowing requires the coordination of 25 muscles and 6 cranial nerves and normal swallowing involves a four-stage process:
1. The initial stage
When eating unassisted, food and drink are conveyed to the mouth under voluntary control and the lips and the jaw close to seal the mouth. Saliva is then produced in response to the sight, smell and taste of food.
2. The oral stage
Also under voluntary control, the food is chewed and mixed with saliva to form a bolus, which is then delivered by voluntary tongue movements to the back of the mouth and into the pharynx (see fig.1).
3. The pharyngeal stage
This is an involuntary stage that is triggered when the food bolus passes through the faucial pillars into the pharynx. The back of the tongue drops and the liquid or food move over the back of the tongue and it then pushes the food or liquid toward the cricopharyngeal sphincter.The soft palate closes the naso pharynx. At exactly the same time the larynx lifts and tilts to shut the airway and the epiglottis completes this closure. The combination of the constrictors and tongue push the food or liquid down and through the cricopharyngeus
4. The oesophageal stage
This stage is also involuntary and begins with the relaxation of the upper oesophageal sphincter followed by peristalsis, which pushes the bolus down into the stomach.
If any one, or more, of these stages in the swallowing process become impaired they will result in dysphagia.
Fig. 1 Anatomy of swallowing process 
Dysphagia is caused by a wide variety of structural or functional conditions and its symptoms can be either acute or chronic.
Acute Symptoms may follow inflammatory conditions like pharyngitits, tonsillitis, aphthous ulceration of the mouth, CVA and the insertion of tracheotomies.
Chronic symptoms of dysphagia can be seen in disorders like Parkinson’s disease, motor neurone disease, neuromuscular disease, multiple sclerosis, and Alzheimer’s disease. Among patients who have had a stroke, as many as 30% suffer from dysphagia [Barer 1989].
Other causes of Dysphagia include: Tumours to the head and neck, surgical procedures, Dementia, Respiratory Disease – COPD or asthma, reduced fluid intakes, polypharmacy and dental problems.
Dysphagia in the elderly
Dysphagia is particularly common among older patients, as ageing can lead to weakened jaw muscles, loss of teeth, reduced sense of smell and taste and reduced salivation.
Older patients are more likely to suffer conditions like dementia, motor neurone disease, Parkinson’s disease, Alzheimer’s disease, multiple sclerosis, cancer and stroke, which can all lead to the impairment of the swallowing process. Dysphagia in older people can also arise as a side effect of medication.
As many as 45% of people over 75 suffer symptoms of dysphagia [European Journal of Public Health Website 1997] and it has been estimated that as many as 66% of those in long-term care experience dysphagia to some extent. Among these patients, dysphagia may have particularly serious consequences, especially in terms of malnutrition and respiratory diseases. Langmore et al (2002) highlight aspiration pneumonia as a serious problem for elderly institutionalised persons. Pneumonia is the second most common diagnosis in nursing home residents and accounts for 21% of all infections.
Despite being a widespread problem among the institutionalised elderly, there is growing evidence to suggest that dysphagia is often under-diagnosed. In a survey of older patients in nursing homes in the UK, Germany, France and Spain, which was carried out in 1999 by the European Study Group for Diagnosis and Therapy of Dysphagia and Globus (EGDG), only 36% of patients received any formal diagnosis of dysphagia.
As dysphagia can have potentially adverse consequences, it is important to establish the exact nature of the patient’s complaint so the problem can be treated appropriately. Often, the patient’s GP or a ward doctor or nurse will have noticed the patient’s symptoms and referred them for assessment by the speech and language therapist working as part of the multidisciplinary dysphagia team.