In this study, it was attempted to reveal the characteristic EEG findings of the epileptics according to their proportion of the abnormal EEG, the distribution of basic rhythms, the responses upon the eye opening and hyperventilation, the proportion of diagnostically significant abnormal wave pattern, their localization, symmetry, synchrony, location, and runs of abnormal wave patterns.
Seven hundred and sixty six cases of the clinical epileptics who had undergone EEG examination because of epileptic convulsion from January 1971 to July 1974 at the Chung Ang University Hospital EEG Laboratory were included in this study.
The results were as follows:
1. Among 766 cases of the clinical epileptics,
53.7%(411 cases) of them showed abnormal EEG findings and 45.3% (355 cases) showed normal. It was revealed that the age group of 4-15 years were higher percentage of abnormal EEG recordings(74.4 %) comparing to the age group of 31-60 years(33.6 %), female group(58.7%) comparing to male group (49.5%), and sleep recordings (67.4%) comparing to waking recordings (50.7%)
2. In the distribution of basic rhythms among 322 cases of abnormal EEG recordings, 85.8% of them
showed normal patterns and 14.2% showed abnormal. Among abnormal patterns, 12.7% were absence of alpha wave, 0. 9% were asymmetrical alpha wave, and 0.6% were irregular alpha wave.
In the EEG responses to eye opening test among 281 cases of abnormal EEG recordings, 81. 5% of them showed normal patterns that alpha waves were replaced by beta waves by the eye opening, and 18.5% showed abnormal. Among abnormal patterns 11.4% were not replaced by beta wave, and 7. 1% were replaced by abnormal wave.
3. Upon the hyperventilation test among 255 cases of abnormal EEG recording, 74.5% of them showed abnormal and 25.5% showed normal. It was revealed that the age group of 4-15 years manifested higher percentage of abnormal EEG recordings (the age group of 31-60 years(67. I%). In this result, it was concluded that hyperventilation test was most significantly useful to EEG diagnosis of epilepsy in younger age groups comparing to older age groups.
4. As to the proportion of diagnostically significant abnormal wave patterns according to the EEG recording of waking and hyperventilation phases, it was revealed that theta wave(19.4% of waking phase, 24.7% of hyperventilation phase), delta wave (77.6%. 76.3%), beta wave (20.2 % . 12.6%). sharp wave (15.2%, 10.5%). and spike(13.4%, 8.4%) were predominantly observed.
In this study, it was also observed that delta wave and 3 cycle per second spike and wave were more frequent by activated by hyperventilation comparing to other wave patterns.
5. The EEG analysis of localization, symmetry, synchrony, location, and runs of abnormal wave patterns in the slow wave groups, the fast wave groups, the spike groups, or the complex groups was revealed as follows.
a) The slow wave groups exhibited tendency to be localized, symmetrical and synchronous wave patterns, predominantly located in frontoparietal region, and frequently showed paroxysmal burst or intermittent runs in waking EEG and paroxysmal burst or gradual build-up in EEG activated by hyperventilation.
b) The fast wave groups exhibited tendency to be diffused, symmetrical and synchronous wave patterns, predominantly located in frontotemporal region, and frequently showed constant runs in waking EEG and depression burst in EEG activated by hypervenlation.
c) The spike groups exhibited tendency to be focalized, asymmetrical and asynchronous wave patterns comparing to other abnormal wave patterns, predominantly located in frontotemporal region, and frequently showed isolated runs in waking EEG and paroxysmal burst in EEG activated by hyperventilation.
d) The complex groups exhibited tendency to be diffused, symmetrical, and synchronous wave patterns, predominantly located in frontotemporal region, and frequently showed paroxysmal burst in waking EEG and parrxysmal burst or diffuse paroxysm in EEG activated by hyperventilation,
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