[Conversion disorders. From neurobiology to treatment].

The two international systems of diagnostic classification for psychiatric disorders, ICD-10 and DSM-IV, differentiate a variety of disorders or syndromes characterized by the common feature of the presence of physical symptoms without "organic correlate." Conversion disorders (DSM) or dissociative disorders (ICD) are historically related to the concept of hysteria. Like psychoanalytical theories, the DSM and ICD refer to a psychological conflict preceding the onset of physical symptoms, although in a purely descriptive manner. The etiology of these disorders is still not very well understood. This article summarizes present knowledge from clinical and epidemiological studies. Functional neuroimaging studies on conversion disorders, although still very rare, allow testing of hypotheses about neuronal mechanisms. Such studies question the traditional and often misinterpreted dichotomy between organic and psychogenic diseases.