Nasopharyngeal stenosis is a typical symptom of obstructive sleep apnea syndrame (OSAS), which is the recurrent occurrence of apnea due to narrowing or obstruction of the upper airway during sleep, leading to a series of symptoms such as hypoxia, irregular heart rate, and even sudden death due to asphyxia, the clinical manifestation of OSAS is snoring during sleep, due to breath-holding and apnea. So what causes this? Nasopharynx (nasopharynx) refers to the part above the plane of the palatal sail that passes forward through the posterior nasal aperture to the nasal cavity. In its lateral wall directly behind the inferior turbinate, there is a pharyngo-pharyngeal opening of auditory tube, which leads to the middle ear tympanic chamber. In front of the pharyngo-pharyngeal opening, there are curved elevations called the pharyngo-pharyngeal pillow (tubal torus). The longitudinal deep fossa between the posterior part of the pharyngeal pillow and the posterior wall of the pharynx is called pharyngeal recess, which is the site of nasopharyngeal cancer. There is rich lymphatic tissue in the mucosa of the posterior superior wall of the nasopharynx, called pharyngeal tonsil, which is more developed in early childhood and starts to atrophy after 6-7 years of age and almost completely degenerates after 10 years of age. In patients with OSAS, the excitability of the oropharyngeal muscles is high in the awake state, and they can compensate for the narrowing of the airway, while in the sleep state, the excitability of the oropharyngeal muscles is high. In the sleep state, the excitability of the oropharyngeal wall muscle groups is reduced and the compensatory ability is decreased, resulting in airway obstruction, which is the reason why snoring patients do not snore or hold their breath in the awake state.