[Syncope. Phenomenology and differentiation from epileptic seizures]

Confusion between syncope and epileptic seizures is a common problem in clinical practice. Recently, new insights into the phenomenology of transient cerebral hypoxia have been gained from video analysis of experimentally induced syncope. Common elements of syncope include multifocal and generalized myoclonus, tonic body extension, automatisms, vocalizations, eye deviations and hallucinations. Thus, it is not the presence or absence of these features but their specific character that distinguishes syncope from epileptic seizures. Other clues for differential diagnosis include precipitating factors, premonitory symptoms and postictal events, such as tongue bites and postictal confusion, which has been identified as the single most powerful factor discriminating syncope from epileptic seizures. In contrast, incontinence and head injury are common in both conditions. Investigations such as electroencephalogram, tilt testing and postictal prolactin or creatine kinase levels may aid diagnosis but are never diagnostic in isolation. In rare cases, hypoxic and epileptic mechanisms may interact within one attack.