Swallowing is a neuromuscular coordinated activity that allows the uninterrupted passage of oral contents (food, liquid, saliva and secretions) into the stomach to pass from the mouth to the pharynx, to the esophagus and into the stomach. The swallowing process is divided into four phases:

1. The Pre-oral Phase begins with the anticipation of food being introduced into the mouth, salivation is triggered by the sight and smell of food.

2. The Oral Phase starts when the lips close and form a seal, chewing and manipulation of food begins, the food is mixed with saliva to form a bolus which is then transferred to the back of the mouth.

3. The Pharyngeal Phase is reflexive initiation of the swallow. The nasal cavity is sealed when the soft palate raises (to prevent food/fluid to go up to the nose). The larynx (voice box) moves upwards and forward, the vocal folds close, and then the epiglottis closes over the airway, to protect it, the pharynx pushes the bolus  down (by contracting in a peristaltic motions) and the upper esophageal sphincter opens to allow the bolus through. Finally, the upper esophageal sphincter closes after the bolus has passed through in order to prevent the bolus moving back up.

4. The Esophageal Phase starts when the bolus is transported through the esophagus by peristaltic motions into the stomach. The lower esophageal sphincter opens to allow the bolus into the stomach and finally the lower esophageal sphincter closes after the bolus has passed through to prevent reflux.

Swallowing disturbances

Difficulty in swallowing known as dysphagia, can be described as any condition that weakens or damages the muscles, structures and nerves used for swallowing. Dysphagia can be categorized according to the swallowing phase that is affected. For example, oral phase dysfunction can occur when there are limited tongue movements, reduced coordination and tonus. Without proper tongue movements, the patient can have trouble forming and manipulating the bolus towards the back of the mouth and the pharynx. When there is dysfunction in the pharyngeal phase such as insufficient closure of the airway while swallowing, food bolus or liquids could enter into the airway and may reach the lungs, a condition called aspiration. This can cause coughing, a choking sensation, a change in voice quality, shortness of breath and can lead to aspiration pneumonia. Esophageal phase dysfunction can occur when there is a disturbance in the esophagus peristaltic motion or when the lower esophageal sphincter does not stay contracted, stomach contents can be regurgitated into the esophagus and even into the airway.

Swallowing disturbances in Parkinson's disease

Swallowing disorders is a common complication experienced by people with Parkinson’s (up to 100%). The severity of dysphagia does not necessarily relate to the overall severity of the disease and it is documented in all phases of swallowing. Parkinsonian patients are “silent aspirators” with decreased cough reflexes, reduced clinical signs and lack of awareness. Silent aspiration occurs when food or liquid enters the airway (trachea) without any reflexive protective behavior such as coughing or choking. Aspiration is seen in more than half of the PD patients and aspiration pneumonia is one of the major causes of death.

Evaluation of swallowing disturbances

Dysphagia evaluation is performed by the speech language pathologist (SLP) in conjunction with other members of the multidisciplinary team. There are two questions to be answered:

1. What type of food is safe for the patient to swallow?

2. What are the therapy goals that should be included during the swallowing intervention program?

The goal of the swallowing evaluation is to examine the oral and pharyngeal phases of swallowing and to assess not only whether the patient is aspirating, but also the reason for aspiration, so appropriate treatment can be initiated.

There are three procedures for evaluation of patients with swallowing disorders: (1) the bed side evaluation or clinical swallowing evaluation that is performed by the speech language pathologist (SLP) and is performed at the clinic or at the patient's room. (2) The videofluoroscopy swallowing study (VFSS) and (3) the Fiberoptic Endoscopic Evaluation of Swallowing (FEES). The VFSS and the FEES are instrumental evaluations and are considered to be the gold standard procedures in swallowing evaluation.

All three methods of evaluation are used to make diagnosis of dysphagia and to guide management based on the findings. A high level of analysis of the swallowing assessment results requires a good understanding of normal swallowing and abnormal patterns to be expected with different underlying medical causes and conditions. A good understanding of swallowing at this level also will lead to significantly better rationales when recommending specific therapeutic intervention.

The importance of early detection of the swallowing disturbances in patients with PD

Early detection and effective intervention can help prevent the serious consequences of dysphagia.It is known that patients' perceptions of their swallowing function are not always reliable, and that existing problems may be undetected if diagnosis relied solely on self‑reporting, probably due to the decreased awareness and knowledge about what are the specific symptoms associated with swallowing problems.Several questionnaires have been developed to use as a screening tool for detecting swallowing problems in PD including Swallowing Disturbances Questionnaire (SDQ) and Eat – 10. Its aim is to obtain information on their swallowing status and detect the swallowing disturbances as early as possible. The screening for swallowing disorders should be routinely administrated at PD centers and can be offered by any health care professionals. Evaluations and treatments of swallowing disturbances should be offered at early stages in order to prevent aspiration pneumonia and maintain the best possible quality of life.

Yael Manor PhD CCC-SLP is an Assistance Professor at Tel Aviv Medical Center, Movement Disorders unit, Tel Aviv, Israel. She has attended/presented at past WPC Congresses. Dr. Manor will be speaking at the WPC 2023 Congress in Barcelona. View the Scientific Program here.

Ideas and opinions expressed in this post reflect that of the author(s) solely. They do not necessarily reflect the opinions or positions of the World Parkinson Coalition®