Of the many conditions that can cause acid reflux disease or GERD, there are some conditions relating to the esophagus  that do not directly involve acid reflux, but may cause similar symptoms, include disorders of control of the swallowing muscles.Principal among these conditions is 'achalasia'. In achalasia, the esophagus goes into 'spasm'. It's easiest to imagine as a form of cramp that affects the muscles of a segment of the esophagus. People with achalasia have difficulty in swallowing, and this usually starts in childhood. At first they find it easier to swallow liquids than solids, but after a while most foods and drinks seem to 'stick' in the chest. If this state is allowed to continue, the esophagus fills with food, like a balloon, and then it suddenly empties upwards into the mouth.That is bad enough, but if it occurs when you are sleeping you can breathe in the food and choke. Sufferers from achalasia may develop repeated chest infections, much like GERD sufferers, from repeated inhalation of food. In the early stages of achalasia, barium swallow X-rays show a bulging lower esophagus above a short narrowed segment that does not open. Later, the bulge becomes much bigger as the esophagus becomes a large soft bag of undigested food.Achalasia is thought to be due to failure of the peristaltic wave to pass through the affected segment of the esophagus, which remains narrow and underdeveloped. The fault lies either in the muscles themselves or in the nerves that co-ordinate their contraction and relaxation.In the early stages of achalasia, the narrowed region can be stretched successfully by an instrument called a bougie or a water-filled dilator. If that isn't possible, and in the later stages of achalasia it  usually  isn't,  then  the  patient  needs  surgery  to  re-fashion  the esophagus just above the cardia, and the cardia itself, to allow food to pass from the esophagus  into the stomach.The operation itself is called 'anterior myotomy' or the 'modified Heller' operation. It is usually highly successful in curing the achalasia, and the grateful patient is delighted to be able to swallow normally for the first time in his or her life.Unfortunately, one of the drawbacks of any form of surgery for achalasia can be the beginning of GERD. The new cardia may allow so much room for passage of food down from the esophagus into the stomach that there is also room for reflux in the opposite direction. So previous surgery for achalasia is a recognized cause of acid reflux and GERD. Most people who do develop it still prefer GERD symptoms to their previous discomfort: it is more easily managed and less of a disturbance to their lives.