[Clinical history: the cornerstone for defining the cause of syncope].

Syncope is a transient loss of consciousness (LOC) due to transient global cerebral hypoperfusion characterized by rapid onset, short duration, and spontaneous complete recovery. However, there are no signs or symptoms specific for LOC due to global cerebral hypoperfusion, and other diseases, commonly defined as non-syncopal 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, must 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, such as falls, drop attack, etc., should be ruled out. Once a LOC is diagnosed, the questions that need an answer are: was LOC with rapid onset and short duration? Did the patient recover spontaneously? If the answers to these questions are positive (therefore, after exclusion of affections such as coma, cardiac arrest, etc.), we are dealing with a transient LOC, which can be an expression of syncope or non-syncopal LOC. From a methodological point of view, we should try to exclude a non-syncopal LOC. Once syncope is diagnosed, we should define the cause. There are some findings in the clinical history that can be considered diagnostic of the cause of syncope. In many other situations, the findings do not permit a definite diagnosis to be made but suggest some causes and, therefore, specific examinations.