Dysphagia is difficulty with swallowing. Swallowing (deglutition) is accomplished in three stages: the buccal, pharyngeal and esophageal phases.
At each level, dysphagia may be caused by inflammation, an obstructing lesion, or by neuromuscular dysfunction. Neuromuscular incoordination may be due to either local factors (physical defects or local nerve damage due to infiltration or surgery) or cranial nerve and brainstem lesions. There is a high incidence of incoordination of swallowing in patients treated with chemoradiotherapy for oropharyngeal cancer.

Causes of dysphagia

Buccal phase: food voluntarily pushed backward by the tongue and palate
- Tumor: intrinsic obstruction, functional deficit
- Stomatitis: infection, radiation, chemotherapy
- Xerostomia
- Neuromuscular: surgery, cranial nerve dysfunction, cerebral or brainstem lesions, general weakness and debility

Pharyngeal phase: swallowing reflex initiated, including glottic closure
- Tumor: intrinsic obstruction, extrinsic compression
- Pharyngitis: infection, radiation
- Neuromuscular: surgery, cranial nerve dysfunction, cerebral or brainstem lesions, general weakness and debility, radiation fibrosis or stricture

Oesophageal phase: food passed down the oesophagus by reflex peristalsis
- Tumor: intrinsic obstruction, extrinsic compression
- Esophagitis: infection, radiation, reflux
- Tube: dislodgement of endoesophageal tube
- Neuromuscular: surgery, mural plexus infiltration, radiation fibrosis or stricture, anxiety

Complications of dysphagia may include aspiration, pneumonia, dehydration, and weight loss.

Treating dysphagia depends on the type and severity of a patient's swallowing difficulty, i.e., for difficulties in the mouth and throat areas, treatments are generally focused on swallowing therapy, including exercises and dietary changes; for problems in the esophagus, treatment options may include surgery or medicine.

Woodruff R. Palliative medicine evidence-based symptomatic and supportive care for patients with advanced cancer. 4th ed. Oxford University Press, 2004. p. 234.