# Electrical Stimulation May Improve the Feeding and Nutritional Status of Children with Dysphagia
## 4 Causes of Swallowing Disorder  
There are several types of dysphagia, depending on which part of the swallowing process is challenging [8; 43]. Oral dysphagia occurs when the problem involves the mouth,most often due to tongue movement disorders. It may also be due to anatomical defects, such as a cleft palate [53]. Pharyngeal or oropharyngeal dysphagia occurs when the issue concerns the passage of food through the throat. Esophageal dysphagia happens when food cannot move down the esophagus [1,2].  
Problems in the oral phase may manifest themselves by avoiding eating, holding food in the mouth, and, secondarily, by fear of swallowing, among other things [39,54]. One of the causes of dysphagia in the oral phase is a dysfunction of the orofacial muscles involved in taking in and swallowing food [2,8,48]. Normally, coordinated muscle contractions move swallowed food toward the pharynx and esophagus and toward the stomach during the esophageal phase [17]. The upper and lower ends of the esophagus have muscle sphinters that allow food to pass from the pharynx to the esophagus and, at the lower end, from the esophagus to the stomach. If the muscles in the esophagus stop working together, or if one of them stops working at all, food may not pass into the stomach [5,13]. This can happen because of problems with the muscles or the nerves that regulate the function of these muscles [38].  
A common esophageal motor problem is achalasia, which is a loss of function of the lower esophageal sphincter [44]. Another is a distal esophageal spasm that can make food go back into the throat [55,56]. The next one is known as a jackhammer esophagus, which refers to the extremely powerful muscle contractions of the esophagus that can lead to severe chest pain during swallowing [57]. It is also possible that the lower esophageal sphincter is either too tight or too loose. If the lower sphincter is too loose, stomach contents can flow back up into the esophagus, or reflux [37]. Additionally, previous esophageal surgery or the insertion of an endotracheal tube can often lead to difficulty swallowing [4,5]. Another factor contributing to swallowing difficulties during the esophageal phase is the presence of structural anomalies. The esophageal narrowing or the formation of pockets in it is an example [58]. An esophageal diverticulum, or pocket-like sac, can form in the lining of the esophagus and trap food that has been swallowed. Sometimes swallowing problems are caused by congenital anatomic defects of the esophagus. However, more often the cause is structural changes that develop over time. These include thickening of the esophageal walls, tumor growth, and other causes that cause the esophagus to narrow [24,58].  
Another cause of dysphagia is neurological issues. Neurogenic dysphagia is related to the nerves that regulate the function of the muscles of the mouth, throat, and esophagus [5,54]. A patient experiencing nasal regurgitation or coughing when swallowing probably has some form of neurological disease [5,45].  
Furthermore, swallowing difficulties may be associated with muscle weakness in conditions such as stroke, amyotrophic lateral sclerosis (ALS), traumatic or surgical damage to the nerves in the head and neck, myasthenia gravis, polymysitis, and Parkinson's disease [24,49].  
In some cases, swallowing disorders may also result from an allergic reaction, causing eosinophilic esophagitis [59]. In time, as a result of frequent inflammatory reactions, a ring-shaped, sometimes supparting, thickening of the esophagus can form, making swallowing difficult. Similarly, any severe infection of the throat or esophagus can make swallowing difficult, but usually this is only temporary and recover after the infection is treated [24].