Resumo

The objective of this work was to create quantitative encephalogram (QEEG) norms for the first year of life. These norms will allow us to have in hand a non-invasive and low cost tool for: a) evaluation of the central nervous system (CNS); b) in case of injury, adequate classification of extent of damage to CNS, and; c) estimation of probable CNS evolution in children at risk in the absence of or in parallel to therapy. These norms have their origin in the calculation of developmental equations which served us to allocate a comparison prototype. From a sample of 101 healthy infants between 15 days and 12 months of age (57 males and 44 females) the normative equations according to age were computed. Later on, for validation the previously obtained norms were applied to the EEG of a different group of 50 healthy infants according to their age. Twenty four artefact-free segments, each of 2.56 seconds and recorded during spontaneous quiet sleep at stage II, were visually selected. The norms were calculated for the entire band spectrum, from 0.39 to 19 Hz in each lead (narrow band analysis) and for the broad bands as well. In order to describe the mean variation of the parameters in relation to age, the regression equations were estimated. The estimation was done using an Iterated Weighted Least Squares method considering variance heterocedasticity. Interpolated maps of the broad band spectral parameters values or their Z transformation were constructed for voltage, average and Laplacian montages. Once the norms were obtained, these were validated by a different group of fifty healthy infants and some pathological cases. The different montages, voltage, average and Laplacian, produced similar tendency curves and similar Z maps of absolute and relative power at all frequency bands. We calculated validation accuracy and this was established between 85% and 88%. Importantly, the QEEG maps of the pathological cases studied showed a high correlation with fMRI images. It is concluded that the QEEG norms obtained by us have a high potential value as an aid to visual interpretation of the QEEG as well as for the diagnosis and evaluation of longitudinal studies within the first year of life. We consider highly significant that the QEEG developmental norms for the first year of life presented here are not only important for the diagnosis of children at risk of damage but as well as for evaluating the further evolution of pathologies and threat of later damage in children at risk.