Histogram analysis of the data obtained by 8 channel EEG apparatus was conducted and compared with those obtained by Offners 830 analyser (Walter-type) in encephalitis japonica, intending to have quantitative representations of typical shapes of EEG or their characteristic shapes in abnormal cases. The clinical simple method of analysis was also applied in hypertension cases, in order to know its clinical use.
In parietal and occipital EEG with recording paper speed of 6cm/sec and frequency of 0-30c/sec, % time of sum of amplitude or frequency in α-, β-, θ-, and δ-bands in histogram method was examined and compared with the % time obtained from α-band spectrum in analyser method. Results in histogram method in hypertension were compared with those of normal cases and the findings of ocular fundi were refered.
1) As to the mean % of each band in histogram method, in case of many waves of large amplitude or of many δ-waves, difference between the histogram of frequency and that of amplitudes was observed, and the latter seemed to be proper practically.
2) Difference between the results of analyser method and that of histogram method was scarcely observed in case of abundance of slow waves, while in case of few slow waves, the difference was remarkable and the results of histogram method resembled to simple observation or routine examination of EEG.
3) Though longer time of analysis in each method is preferable to get preciser esult, it may be shortened from 1min. to 20 sec. or 12 sec., if error of 5% is allowed.
4) No different result was observed in histogram analyser on the same case.
5) Mean % of each band in hypertension differed from normal.
6) Two histogram analyses varying selective standard of slow waves amplitude were conducted on the data in hypertension. Comparison of results of the two analysis revealed thatslow wave with low amplitude (below 30μv) gave marked influence upon the clinical meaning of histogram analysis.
Histogram method gave similar result to the mere diagnosis of EEG. The method may be of wide application in daily clinical investigation.
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