A quantitative relationship between the extent of localized cerebral lesions and the intellectual and behavioural deficiency in children

In an investigation of 51 children with localized forebrain lesions (25 left hemispheric, 15 right hemispheric and 11 bilateral) a significant relationship between the extent of the cerebral lesion (quantitatively determined by means of computerized tomography scans) and the IQ was found, but only in children with lesions after age 5: there was a diminution of 3 (British Ability Scales and Porteus Mazes) to 4 (Wechsler test) points of 10 for a 1% increased brain lesion. There was no correlation between the extent of the lesion and IQ in children with early lesions. The IQ of the children with early lesions (up to year 4) was significantly lower than that of children with later lesions of the same extent.