Syncope due to glossopharyngeal neuralgia or other visceral disease: this type of syncope is rare. Transient syncope occurs during lingual-pharyngeal neuralgia, biliary colic, renal colic, bronchial or gastrointestinal endoscopy. It is associated with severe pain and hyperreflexive response of visceral receptors. So, what are the causes of syncope caused by patients with glossopharyngeal neuralgia or other visceral diseases? The following is a brief description: The most basic reason for the occurrence of syncope is the temporary lack of cerebral blood supply, so it is useful to understand some issues related to cerebral blood flow for further understanding of syncope. The adult brain weighs about 1500 grams, accounting for 2% to 2.5% of body weight. While cerebral blood flow accounts for 15% of the whole body blood flow, brain oxygen consumption accounts for 20% of the total body oxygen consumption, and up to 40% in children. Normal adult blood flow per 100g of brain tissue per minute is 40-50ml, and if it is reduced to 31.5ml, symptoms of cerebral ischemia will occur. Therefore, it is necessary to ensure normal cerebral blood flow. The amount of blood that must flow through the brain in a normal person in 24h is about 1700L, and the consumption of oxygen is about 72L. Cerebral blood flow is closely related to effective perfusion pressure and cerebrovascular resistance, and also related to intracranial pressure, blood viscosity and vascular caliber. For example, cerebral blood flow increases when thinking, high fever and anxiety, and decreases when body temperature decreases, but the fluctuation range of cerebral blood flow is limited. The autoregulation of cerebral blood flow is a guarantee that the necessary blood flow is available for normal brain tissue activity. Under normal conditions, due to cerebrovascular autoregulation, changes in systemic blood pressure do not affect cerebral blood flow, and when blood pressure rises, cerebrovascular resistance increases, and when blood pressure falls, cerebrovascular resistance decreases, so that cerebral blood flow remains constant. This protective cerebral blood flow autoregulation function is lost. Blockade of α-adrenergic receptors has been shown to lower the lower limit of blood pressure to 4.7 kPa in experiments, so it is believed that the autoregulation of cerebral blood flow is achieved through innervation. However, there are other factors that can affect cerebral blood flow, such as carbon dioxide and oxygen concentration in arterial blood, blood viscosity, and vascular caliber. If cerebral blood flow stops for 6-7 min and the partial pressure of oxygen in the blood is lower than 2.7 kPa, serious brain dysfunction can occur because brain cells cannot carry out normal oxygen metabolism.