Dysphagia is defined as difficulty in swallowing. The cricopharyngeal muscle or the upper esophageal sphincter is normally persistently contracted except during swallowing. Cricopharyngeal muscle spasm results from failure of complete relaxation of the muscle and/or its early contraction. 

A hiatus hernia is defined as a protrusion of the upper part of the stomach into the thoracic cavity. There are four types: sliding, para-esophageal, mixed and mixed with herniation of other viscera. Patients can complain of reflux symptoms all in types except in the para-esophageal type as the gastro-esophageal junction is at its normal intra-abdominal site (i.e. is not intra-thoracic).

Special thanks to Dr Bahaa Al-Dein Mahmoud.