**4. Clinical features and diagnosis of dysphagia in Parkinson's disease**

Oropharyngeal dysphagia in PD may limit or preclude safe oral feeding, reducing the patient's full capacity in society and resulting in social, psychological, and economic problems for the individual [27].

One of the first reports of parkinsonian dysphagia was in 1817 by James Parkinson, who described a typical case of PD with weight loss, difficulty in swallowing solids and liquids, sialorrhea, and reduced tongue movements [21].

In 1983, Longemann proposed the videofluoroscopic swallowing study (VFSS) as a means of assessing the dynamics of swallowing. Parkinsonian VFSS [27] can show specific impairments, such as those in the oral pharyngeal and esophageal phases. In the oral phase, these include orofacial tremor, difficulty forming a cohesive food bolus, prolonged swallowing time, limited tongue and mandibular excursion during mastication, and the presence of repetitive antero‐ posterior movements of the tongue during bolus propulsion (lingual festination). Pharyngeal phase impairments include delayed pharyngeal response with consequent stasis in the valleculae and piriform sinuses, with the risk of laryngeal penetration and aspiration, and impairment of pharyngeal muscle contraction and cricopharyngeal function [28]. Impairments in the esophageal phase of swallowing include reduced peristalsis and reduced transit time. All of these disturbances occur together with the traditional motor symptoms of PD (brady‐ kinesia and rigidity) as a result of degeneration of the autonomic nerve system and voluntary muscle system [29, 30].

The incidence of swallowing disorders in PD varies from 50% to 100% of patients. Another characteristic reported in studies of dysphagia in PD is that it may be present without symp‐ toms, making it difficult to identify the condition early and, consequently, to plan a more efficient therapeutic approach [27].

Interestingly, many patients who do not complain of feeding difficulties report having eliminated certain types of food that caused them swallowing difficulties, often restricting themselves to food with a purée consistency. Some patients report weight loss associated with swallowing disorders.

As a result of swallowing disturbances, parkinsonian patients may present with tracheal aspiration (entry of material into the airway), which is generally asymptomatic and known as silent aspiration. Tracheal aspiration related to swallowing is a major cause of morbidity and mortality in PD, suggesting a reduction in voluntary mechanisms that protect the upper airways [31].
