Amplitude spectral analyses of disorganized patterns on electroencephalograms in preterm infants

The aim of this study is to clarify the differences of EEG activities according to the presence or absence of disorganized patterns using amplitude spectral analysis. We compared EEGs of 17 preterm infants with disorganized patterns with those of 34 matched controls. Amplitude was defined as a square root of EEG power analyzed by fast Fourier transform algorithm, and was calculated in the 9 frequency bands. Six EEG segments of 10 s were collected from the part of EEG with continuous high voltage slow waves in the absence of artifacts. The results were separately evaluated according to the post-conceptional age at EEG recordings. In patients with disorganized patterns, reduced amplitude of delta waves in the central areas and increased amplitude of beta waves in the occipital areas were observed at 29-30 weeks of post-conceptional age. The results were almost similar at 31-32 weeks of post-conceptional age. Amplitude in theta or alpha frequency bands was not different between those with and without disorganized patterns either at 29-30 or 31-32 weeks of post-conceptional age. Amplitude spectral analyses will contribute to objective evaluation of disorganized patterns.