The most common causes of transient loss of consciousness, called syncope, are: 1. Cardiac causes. The most common causes of syncope are: 1) cardiac causes, such as third-degree atrioventricular block, which can lead to a decrease in heart pumping, resulting in transient ischemia in the brain and loss of consciousness. 2) cerebrovascular causes. Such as posterior circulation ischemia, etc., can cause loss of consciousness due to insufficient blood supply to the brain. 3, epilepsy. Loss of consciousness is induced by excitation and discharge of nerve cells in the brain, but is mostly accompanied by limb twitching. EEG can find epileptic waves. 4, hypoglycemic reaction, can appear loss of consciousness, sweating and other manifestations, check blood sugar below 2.8 mmol/l can confirm the diagnosis. There is also reflex syncope, such as urinary syncope, which needs to exclude organic diseases before consideration. In short, we need to improve the corresponding auxiliary examination to clarify one by one.