Motor Disorders of the Upper Digestive Tract Review. Clinical Classification of Swallowing Disorders and the Resulting Mechanism of Aspiration.

Aspiration resulting from swallowing disorders can be classified into four types. This classification is helpful for selecting an appropriate surgical treatment for the aspiration as well as for difficulty in swallowing.Type I: In this type, aspiration ccurs when the larynx is elevated and closed during swallowing. It results from an incomplete laryngeal closure.Type II: Here aspiration takes place when the larynx descends and opens at the end of the second stage of swallowing. This type aspiration results from a weak propelling force and/or a strong resistance at the entrance to the esophagus. The weak propelling can be attributed to an incompetent velopharyngeal closure, disturbances of tongue movement and/or a weak pharyngeal peristalsis.Type III: Aspiration occurs in both the rising and falling phases of the larynx.Type IV: This type is observed in those patients who are unable to execute the movements of the second stage of swallowing. The inability for the second stage movements seems to be caused by one of the following two factors: a severe paralysis of the swallowing muscles and strong inhibitory stimuli to the swallowing center of the medulla oblongata. The latter is observed in those patients who would have a very severe aspiration if their swallowing center allowed them to swallow. In this type, the bolus is transported from the mouth to the pharynx by gravity and weak tongue movements. The larynx closes as a reflex action but does not present the type of rising and falling movement by executed in the normal second stage. When the larynx opens, the bolus in the pharynx enters the airway.