Development of the temporal lobe in infants and children: Analysis by MR-based volumetry

BACKGROUND AND PURPOSE: Recent advances in data-processing techniques have allowed more accurate MR-based volumetric measurement than was possible in the past. The purpose of this study was to use this technique to evaluate t he development of the temporal lobes in childhood. METHODS: The study group consisted of 42 subjects aged 3 weeks to 14 years (mean age, 5 years), all with normal findings on a routine MR study and non e with a history of epilepsy. MR images were acquired on a 1.0-T system usi ng a T1-weighted 3D ultrafast gradient-echo sequence, The volumes of the hi ppocampal formations and temporal lobes were measured by using a workstatio n, and the percentage of hippocampal formations in the temporal lobes was c alculated. Myelination in the limbic system and related structures was also evaluated. RESULTS: The volume of the hippocampal formations increased sharply until t he age of 2 years, and continued to increase slowly thereafter. However, th e percentage of hippocampal formations in the temporal lobes showed a negat ive correlation with age. The hippocampal formations on the right side were larger than those on the left in 38 cases (91%), and the anterior temporal lobes on the right were larger than those on the left in 32 cases (76%), T his right-left asymmetry of the hippocampal formations and anterior tempora l lobes was observed from early infancy, and these differences were statist ically significant, A longitudinal fasciculus of high signal intensity was seen in the white matter beneath the subiculum by about 3 months of age. CONCLUSION: MR-based volumetry established developmental characteristics of the temporal lobe, such as a hippocampal growth spurt, a growth difference between the hippocampal formation and the rest of the temporal lobe, and r ight-left asymmetry. Knowledge of these characteristics may aid in the unde rstanding of hippocampal and temporal lobe abnormalities in children.