A CLINICAL STUDY OF THE RELATION BETWEEN SPASMS IN SERIES AND PERIODIC EEG ABNORMALITY IN EPILEPTIC ENCEPHALOPATHY BEGINNING IN EARLY INFANCY

Objectives: The mechanisms causing epileptic spasms to repeat periodically in series have not yet been clarified. We tried to elucidate the pathophysiology of spasms by investigating their relation to the suppression-burst EEG pattern, because it is the most remarkable manifestation of periodic tendency intrinsic to immature brain function in early infancy.

Methods: In a 3-month-old boy with Ohtahara syndrome and a 3-month-old girl with early myoclonic encephalopathy (EME), the beginning or ending process of the ictal EEG activity of clustering spasms was examined by temporally compressing the records. Gamma rhythm with a frequency faster than 50Hz was studied in the ictal activity of spasms and in the interictal suppression-burst in EEG by temporally expanding the records and also by using spectral analysis. Myoclonus occurred, accompanying the EEG bursts in the patient with EME, and it was also analyzed.

Results: A mutual transition was found between the suppression-burst pattern and the ictal activity of spasms in the compressed EEG. Gamma rhythm was observed in the expanded ictal EEG of spasms, and it was also detected in the bursting activity of interictal EEG. Similar gamma rhythm was noted in association with myoclonus in the patient with EME. Therefore the presence of a common pathophysiology was indicated in spasms, the EEG bursts, and this type of myoclonus.

Conclusion: It was suggested that in these patients the mechanisms causing periodic bursting activity in interictal EEG were closely related to the generation of spasms.