Changes in frontal lobe size with age. A CT study in children.

A series of linear measurements on computed tomography of the brain was performed in 481 children (from newborns up to 5 years of age). Each measurement increased with age in infancy and early childhood. In addition to the commonly used linear measurements, a new index has been devised. This index equals the ratio between the sagittal diameter of the brain and the sagittal midline distance from the anterior border of the brain to a line tangential to the anterior horns. All measurements were made on the scan at the level of the foramen of Monro. This index was called the frontal force index (FFI), because it seemed to reflect the morphologic change in the frontal lobes. The functions related to the frontal lobes, i.e. cognitive functions, develop rapidly during infancy and early childhood. In normally or subnormally developed children the FFI increased during early infancy and decreased in severely retarded children. The FFI is obviously useful in the evaluation of the development of the frontal lobes.