Analysis of the electroencephalogram of children by histogram method

Abstract

For the quantitative expression of slow activity of the EEG, the writers analysed the EEGs of 87 children by analyser and histogram methods and two of these EEGs were also analysed by the mathematical method. The histogram method was also applied to the study comparing EEGs of children having sign of some neuropsychiatric condition with those of normal ones and its clinical usefulness was assessed. 1. 1. An Offner type 830 analyser was used and the quantification of each band (delta, theta, alpha and beta) activity was achieved by calculating the percentage of total voltage of the band, that is, the percentage of the square root of the squared sum of every deflection in the band. Although this method of analysis is the most advantageous, there remain some theoretical and technical problems to be solved. 2. 2. The mathematical method of analysis is the most rational one. However, its procedure is too tedious for practical use. The results of these two methods of Fourier analysis (analyser and mathematical methods) coincided fairly well with one another, but the results of these two methods were somewhat different from our impression gained from original record by visual inspection, as slow components were rather emphasized. 3. 3. In the histogram method, standards to measure amplitude and period of each wave were provided in order to exclude subjective criteria. The results of this analysis were to us the most easily understandable ones, as they were the most similar to what is obvious by visual inspection. The procedure of this analysis is rather laborious, but it was found that allowing for 5 per cent error, 20 sec. could appropriately be used instead of 1 min. as the period of analysis. 4. 4. EEGs of 95 mentally deficient Junior High School boys and girls (I.Q. below 80) ranging in age from 13 to 17 years were recorded and 83 EEGs which did not show any specific wave such as “spikes” were analysed by the histogram method in comparison with EEGs of 30 normal Junior High School boys ranging in age from 13 to 15 years. In general, the percentage of slow bands in mentally deficient children were larger than those in normal children and in 47.0 per cent of 83 EEG records from parietal regions, the slow band percentages were abnormally large. The histogram method was also applied to the EEGs of 27 children who suffered from encephalitis japonica and it was found that there existed a fairly good correlation between the percentage of the delta band and the seriousness of the disease. From these results, it may therefore be said that the histogram method is applicable in clinical practice, although it has no theoretical basis.