Syncope manifests as a transient state of loss of consciousness due to transient cerebral insufficiency of blood supply, often accompanied by decreased muscle tone and inability to maintain a certain body position. Syncope is one of the common clinical conditions in children, and its causes are complex, including neurally mediated (reflex) syncope, syncope due to cerebrovascular disease, psychogenic syncope, cardiogenic syncope, metabolic syncope, and unexplained syncope; among them, neurally mediated syncope is the more common cause, and vasovagal syncope is the most common type of syncope; although the incidence of cardiogenic syncope is low, its onset is rapid and dangerous, and should be taken seriously. The incidence of cardiogenic syncope is low, but its onset is rapid and dangerous and should be taken seriously. There are many causes of syncope, and the clinical understanding of its primary disease, Huang Min of the Department of Cardiology, Shanghai Children’s Hospital, directly affects the prognosis of the child and the outcome of the disease. Syncope is one of the common clinical conditions, and it occurs mostly in older children and adolescents. 15.5% of male college students had syncope in the Guzman-Perry survey, and 22.3% of the U.S. Air Force had syncope in the Collins report. Breath-holding in infancy is similar to syncope, and Menkes estimated that 5% of children aged 5 months to 6 years had a history of breath-holding-like episodes, and that the incidence of syncope was higher in these infants as they grew older. The incidence of syncope is higher in females than in males (2:1), and there are 2 peak age groups for the incidence of syncope, adolescents and older adults, with the peak age of onset in adolescents being between 15 and 19 years. The etiology of syncope is complex, with neurally mediated (reflex) syncope being the most common cause, and vasovagal syncope (VVS) being the most common type of reflex syncope, with data showing that neurally mediated syncope is the most common (60%-71%), followed by cerebrovascular and psychogenic syncope (11%-19%), and cardiogenic syncope (6%). Syncope is generally not life-threatening, but recurrent syncope will seriously affect children’s physical and mental health and quality of life, cause extreme anxiety in family members, and easily lead to accidental injury in adolescents, so it is of great concern; at the same time, there are many causes of syncope, and its primary cause has a great impact on the prognosis and regression of the patient. Neurally mediated syncope, also known as reflex syncope, is the most common type of clinical syncope, including vasovagal syncope, carotid sinus syndrome, context-related syncope, and painful syncope, and can be seen in all ages. The mechanism of occurrence is not fully understood, but some children may experience a reflex increase in vagal activity and a decrease in sympathetic activity due to activation of receptors in the bladder, esophagus, respiratory tract, carotid sinus, and other organs. Vascular vagal syncope is the most common cause of syncope in children, accounting for 80% of all children with unexplained syncope. The autonomic nervous system plays a fundamental role in the pathogenesis of VVS, and genetic polymorphisms may lead to alterations in adrenergic receptor function and subsequent dysregulation of the autonomic nervous system. VVS episodes can be episodic, i.e., more frequent over a period of time, decreasing or stopping on their own after a period of time, and are more likely to occur in girls aged 11-19 years, usually triggered by prolonged standing or seeing blood, severe pain, hot environments, hot baths, exercise, or stress. Before the onset of the disease, there may be aura symptoms: transient dizziness, inattention, pale face, reduced visual and auditory perception, nausea, vomiting, sweating, unstable standing, etc. Syncope mainly manifests as falling, blood pressure drops, heart rate drops, weak pulse, pale face, loss of consciousness, some patients appear incontinence, slight convulsions, symptoms usually last for a few seconds to 2 minutes, after waking up, general weakness, dizziness, thirst, etc. The symptoms may be followed by vomiting and fulminant diarrhea. 2, postural tachycardia syndrome The affected children are mostly school-age children, and the incidence is higher in girls than in boys. The child has the following symptoms when standing upright: dizziness or vertigo, chest tightness, headache, palpitations, facial changes, blurred vision, lethargy, morning sickness, syncope in severe cases, etc. These symptoms are alleviated or disappear after the child lies down; although it often occurs in the standing position, it can also occur in the sitting position. 3, upright hypotension Due to the sudden change from the lying or squatting position to the sitting or standing position, causing a drop in blood pressure. The occurrence of this disease may be related to autonomic dysfunction, and some patients have a family history. Simple upright hypotension, mostly seen in adolescents, is associated with dizziness, palpitations, shortness of breath, pallor, cold sweats, nausea and unsteadiness in standing; secondary upright hypotension, mostly seen in neurological disorders, hematopoietic disorders, malnutrition, drug effects or allergies. The diagnosis of neurally mediated syncope mainly relies on the upright test or the head-up tilt test (HUT), which is simple to perform and less dangerous. The HUT had a high sensitivity (55.4%) and specificity (100%) for the diagnosis of pediatric vasovagal syncope. Context-related syncope refers specifically to syncope occurring in certain contexts (1) Urinary syncope: Syncope commonly occurs in male children before, during, or after urination, especially when getting up from the prone position. The cause is still unclear, because the sudden release of pressure in the bladder causes vasodilation and reduced venous return, coupled with the force of breath holding during urination, which reduces cardiac output, and vagal reflex-mediated bradycardia is also a contributing factor. (2) Defecation syncope: The occurrence of syncope or aura of syncope during defecation is called defecation syncope. It often indicates the presence of underlying gastrointestinal, cardiovascular, or cerebrovascular disease. It can occur in children and can be recurrent. (3) Cough syncope: Often occurs after a bout of coughing and the child suddenly develops weakness and brief loss of consciousness. There are three possible mechanisms for syncope: first, the paroxysmal cough increases the pressure in the thoracic cavity, affecting venous return, lowering cardiac output and lowering blood pressure; second, the increased pressure in the pleural cavity is transmitted to the skull, raising intracranial pressure; third, the cough decreases blood CO2 tension, increases cerebrovascular resistance, and decreases cerebral blood flow, causing syncope. (4) Swallowing syncope: It is mainly manifested as syncope or aura of syncope when the child swallows or swallows too hot or too cold food or even at the sight of food. It is usually associated with esophageal or peripharyngeal injury or linguopharyngeal nerve palsy. (5) Carotid sinus syndrome: Rarely seen in children, syncope occurs mainly due to a slight overpressure response of the carotid sinus, causing overexcitation of the vagus nerve, leading to sinus bradycardia, sinus arrest or atrioventricular block, and resulting in syncopal episodes. Syncope in these patients often occurs when the head is turned to one side or the collar is too tight, or when lesions near the carotid sinus, such as enlarged lymph nodes, tumors, or surgical scars, compress the carotid sinus. Syncope occurs without aura symptoms such as nausea and pallor, and loss of consciousness usually lasts no more than a few minutes, followed by complete recovery. Carotid sinus massage is an important method to diagnose carotid sinus allergy. (6) Autonomic dysfunction: Autonomic dysfunction includes primary diseases such as primary autonomic failure and multi-system atrophy and some secondary autonomic failure, such as secondary to Parkinson’s syndrome (parsons’ disease) or diabetes mellitus. The pathogenesis is mainly due to autonomic dysregulation, decreased blood volume, and the accumulation of blood mainly in the lower extremities when standing, resulting in a drop in blood pressure, dizziness, and even fainting in severe cases. Cardiogenic syncope Cardiogenic syncope is caused by a variety of pathological mechanisms such as rapid or slow fatal arrhythmias and acute mechanical dysfunction of the heart, which dramatically reduces cardiac output and causes acute cerebral ischemia. Compared to other types of syncope, its incidence is lower in the pediatric period, but it is more clinically urgent and dangerous, often triggering sudden death.