Initial evaluation of the patient with transient loss of consciousness

Syncope is a transient loss of consciousness (LOC) due to transient global cerebral hypoperfusion characterized by rapid onset, short duration, and spontaneous complete recovery. Unluckily, there are no signs/symptoms specific for LOC due to global cerebral hypoperfusion, and other disorders, commonly defined as nonsyncopal LOC, can induce transient LOC with other mechanisms. Moreover, since there are many causes of transient LOC, an adequate method in taking clinical history, which is the cornerstone of diagnosing patients with transient LOC, should be utilized. The first question to be answered is whether the patient had a real LOC, characterized by loss of postural control and unresponsiveness. Therefore, events with similar clinical features, as falls, should be excluded. Once a LOC is diagnosed, the questions that need answers are: was LOC with rapid onset and short duration? Did the patient recover spontaneously? If the answers are positive, we are dealing with a transient LOC, which can be an expression of syncope or nonsyncopal LOC. From methodological point of view, we should try to exclude a nonsyncopal LOC. Once a syncope is diagnosed, we should define the cause.