Achalasia is the impairment of the smooth muscle of hollow organs, that is characterized by a lack of muscle tone release (relaxation).In most cases the term achalasia is used to describe a motility impairment of the lower parts of the esophagus (esophageal achalasia), that is caused by degenerative changes in the myenteric plexus.The opposite of achalasia is chalasia.Source: Endoskopie-Atlas
