Introduction
Syncope is defined as a loss of consciousness secondary to decreased cerebral perfusion pressure occurring in brain areas responsible for a state of alertness which include the bilateral cortex, the reticular activation system, and the brainstem.
Syncope in children is a not uncommon clinical condition estimated to occur in 126 out 100,000 children with cardiogenic and neurogenic causes representing 80% and 9% of cases, respectively. Other etiologies include metabolic, psychological, and toxicological causes, as listed below.
Syncope at rest
Syncope that occurs when the patient is in standing position or that occur when moving from a supine to sitting position can be a type of vasovagal response. This is characterized by a systemic hypotension secondary to a sudden loos of vasomotor tone known as the vasodepessor response. If it is also accompanied by significant bradycardia or aystole it is termed a cardioinhibitory response.
This type of syncope happens most frequently when the patient has been standing for prolonged periods of time such as in church or at a military parade or after a period of sleep. The loss of consciousness is brief (1-2 minutes) and often an emotional or physiological component such as dehydration, fatigue, hunger and other illness contributes to precipitating the event.
Syncope during activity
Syncope during physical activity demands a workup for an underlying cardiac abnormality that causes an inability of the body to meet the increased cardiac output requirement. The differential diagnosis should include Wolff-Parkinson-White syndrome, long QT syndrome (LQTS), hypertrophic obstructive cardiomyopathy, and more rare arrhythmogenic right ventricular dysplasia. In all cases, a careful family history for syncopal episodes, sudden unexplained death, and seizures should be obtained.
Causes of Syncope in Children
Autonomic
vasovagal (fainting) – most common cause in children
excessive vagal tone – adolescents, athletes
reflex – micturation, cough, hair grooming, breath holding
orthostatic – blood loss, dehydration
Cardiac
obstructive lesions – hypertrophic obstructive cardiomyopathy, aortic stenosis, primary pulmonary hypertension,
arrhythmia – long QT syndrome, heart block, ventricular tachycardia, supraventricular tachycardia
hypercyanosis – Tetralogy of Fallot episodes
miscellaneous – myocardial infarction, anomalous coronary artery
Non-cardiac
neurologic – seizures, migraine
metabolic – hypoglycemia
hyperventilation
psychological
vascular – vertebrobasilar insufficient
(adapted from Avoiding Common Pediatric Errors, p. 301)
Physiological symptoms of sleep paralysis are the same with those of syncope. Thus, sleep paralysis is caused by syncope. For experts in cardiovascular diseases, sleep paralysis or syncope is a common symptoms of cardiovascular disease. For a long time, due to the ignorance of physiological knowledge of syncope , ischemie cerebrale , slow beat, fast beat and so on, psychological illusion in people’s sleep generated by such physical symptoms i.e. the nightmare really has puzzled the psychologists, therefore they put forward a wide range of wrong even absurd views on the nightmares, which both have no scientific basis, and could not be confirmed, even more were not self-consistent. For example, a medical expert Debacke drew the correct conclusion that the anxiety-dream resulted from ischemie cerebrale according to the physiological symptoms of the anxiety-dream of a boy of thirteen. Freud called such view was a ” medical mythology” in the book of Dream Psychology. Most important,the experiment confirmed the idea. For example, a place in country , there is a “haunted” bed which makes people have sleep paralysis or syncope every night, and it is this fact that the pillow in the bed is too high will reduce cerebral blood flow.