Neurocardiogenic syncope is the most common reason for fainting. It is also called vasovagal syncope.
In neurocardiogenic syncope, blood pressure rapidly falls, and blood flow to the brain becomes very low. The person loses consciousness (passes out or faints), usually for only a few seconds.
Neurocardiogenic syncope can occur suddenly, in response to a startling event or strain (a needle stick, pain, fear, cough, or defecation). It can also occur after prolonged standing, heat exposure, or exertion. Some people experience a period of ill-feeling for a few minutes before actually passing out.
Neurocardiogenic syncope is common and usually does not signal any serious problem or increased health risk. However, there can be many other reasons for fainting (syncope), some of which are serious. After a fainting episode, further testing is often recommended to make sure a serious cause of syncope (such as an abnormal heart rhythm) isn’t responsible.