There are a large number of different causes of swallowing difficulties. If it has been present for more than 3 weeks it should be checked out with an endoscopic examination of the throat.
There are several causes for swallowing difficulties:
Obstruction- This can either be from within the throat or gullet (oesophagus) such as a lump of food or pushing in from the outside such as an enlarged thyroid gland (goitre).
Neurological- There is a complex system of muscular reflexes which allow the swallowing mechanism to work. If there is an abnormal tightening of these muscles (cricopharyngeal spasm) or a breakdown in the co-ordination of the muscle contractions then difficulty swallowing occurs. If there is a failure of some of the nerves to work, such as a vocal cord palsy, then food can go onto the chest and cause a cough reflex and risk chest infection.
Other- Several other unique things can go wrong in the throat causing swallowing difficulties. One of the more common is a pharyngeal pouch where an out-pouching of the lower throat forms on the inside. Food can become stuck in this and then regurgitate back into the mouth. Globus is also associated with some swallowing difficulties.