[Mental deficiency: organic aspects]

This review of the organic aspects of mental retardation considers this handicap among the other chronic neuropediatric disorders and is one of the numerous possible manifestations of a cerebral damage occurring in a developing nervous system. The relative frequency of the different etiologies is discussed in relation to the severity of the mental handicap. The prenatal causes of mental deficiency which are the most frequent are reviewed and a distinction is made between malformations and pseudomalformations. Particular mention of the fetal alcohol syndrome is made. The role of perinatal medicine in the epidemiology of mental retardation is discussed and the diagnostic approach of a particular child with mental retardation is presented with the personal experience of the author in the pediatric department, CHUV, Lausanne. The possible measures to prevent mental retardation are finally discussed.