Syncope is an abrupt, transient, and complete loss of consciousness associated with an inability to maintain postural tone, followed by rapid and spontaneous recovery. Syncope is caused by temporary cerebral hypoperfusion. Presyncope describes symptoms such as lightheadedness and vision changes that may or may not precede syncope. Syncope can be classified by its mechanism: reflex (neurally mediated), orthostatic hypotension, or cardiac. Initial evaluation of loss of consciousness should include a careful history and detailed physical examination with orthostatic vital signs and 12-lead electrocardiography. The history should evaluate whether the episode was a true loss of consciousness and clarify whether it has a syncopal or nonsyncopal etiology. Although there is no evidence-based standard for the diagnosis of syncope, consensus suggests diagnostic criteria concordant with the three syncope mechanisms. The treatment of syncope is specific to its mechanism. Multiple risk stratification tools exist; however, these do not outperform clinician judgment in predicting serious outcomes of syncope in the short term. When evaluating and treating syncope, additional consideration should be given to special populations including children and adolescents, older adults, athletes, and patients with postural orthostatic tachycardia syndrome.

Case 3. LH is an 18-year-old, otherwise healthy college student and vocal performance major who presents after several episodes of passing out at school. She states that these episodes have occurred randomly. She suddenly feels lightheaded, even if she has eaten recently. Before the episodes of passing out, or feeling like she will pass out, she has some nausea and blurry vision, but has not had headache, chest pain, or any neurologic signs or symptoms.