Syncope.

In brief Syncopal episodes are usually benign, but some causes can be life-threatening. The differential diagnosis is extensive and includes vasovagal reaction, decreased intravascular volume, metabolic disorders, cardiac disorders, medication use and abuse, Valsalva maneuver, and intracranial conditions. A detailed account of the event and a medical history direct the workup. Combining a thorough physical examination that emphasizes the cardiovascular and neurologic systems with selective laboratory tests and noninvasive diagnostic studies may reveal why the patient lost consciousness during his or her athletic activities.