[Epileptic evolutive encephalopathies in infants (West tsyndromee and Lennox-Gastaut syndrom) (author's transl)].

Electroclinical aspects of the West syndrome are studied in their atypical forms: clinical and EEG characteristics, partial forms, Aicardi syndrome. Etiological investigations (especially CT scan) are necessary to distinguish the more frequent 'secondary forms' from the 'primary forms'. The etiological factors are: (i) Prenatal causes (hereditary affections, chromosome-related etiology, fetal etiology; (ii) Perinatal causes (prematurity, traumatic delivery); (iii) Postnatal causes (infectious diseases). The evolutive aspects and prognosis are different for 'primary' and 'secondary' forms. The time of commencement of the mode of therapy and its duration are important factors in relation to the prognosis of 'primary forms'. A pre-existing encephalopathy obviously leads to a very poor prognosis. A typical Lennox-Gastaut syndrome can be observed in infants. However, atypical forms are more frequent. These too have a poor prognosis because they are usually secondary to cerebral lesions.