Severe Mental Retardation in a Swedish County – II. Etiologic and Pathogenetic Aspects of Children Born 1959–1970

Abstract

In an unselected series of 122 children born from 1959-1970 with severe mental retardation (SMR), the magnitude and distribution of different etiologic and pathogenetic factors were analyzed. Prenatal causes were considered relevant in 73%, perinatal in 10% and postnatal in 3%. In 12% no traceable cause was found. Infantile primary psychoses constituted 2%. Within the prenatal group, no less than 43% presented firm evidence favoring a genetic etiology, chromosomal syndromes together constituting 36% and mutant gene disorders 7%. Etiologically unclassifiable cases with prenatal stigmata and congenital defects amounted to 18%. A condition of fetal deprivation of supply apparently was of major importance in 8%. Almost half of the cases had 1 or more associated CNS handicaps. Cerebral palsy syndromes were evident in 18% and epilepsies in 30%. The relative risk of having cerebral palsy in addition to SMR was strongly correlated to cases classified as prenatally or perinatally acquired CNS syndromes. Prenatal prevention apparently is of special importance for reducing occurrence of SMR. As chromosomal aberrations are the cause in more than 1/3 of cases with SMR, the desirability of developing effective cytogenetic screening methods and programs applicable to all pregnant women was emphasized.