Nerves stimulate muscles in the wall of the esophagus, in order to propel food and liquids down the esophagus and into the stomach. A muscular ring at the bottom of the esophagus, called the lower esophageal sphincter, prevents food from leaking from the stomach, back into the esophagus. For reasons that are unclear, the nerves that control this process do not function correctly.

The abnormal nerve function causes two problems:

• Muscles in the wall of the esophagus do not propel food down the esophagus correctly.
• The lower esophageal sphincter does not open correctly, obstructing the flow of food into the stomach.