Selected Papers: MEG, EEG

Abstract

Abstract *Fumika Endoh, †Harumi Yoshinaga, †Tatsuya Ogino, †Tomoyuki Akiyama, †Hodaka Ohta, and *Eiji Oka *Department of Child Neurology, Okayama University Graduate School of Medicine and Density, Okayama, Japan ; †Department of Child Neurology, Okayama University Medical School, Okayama, Japan . Purpose: The aim of this study was to clarify the characteristics of epileptic discharges in early infancy. A retrospective electroclinical study was conducted on high-risk infants, and the relationship between their postconceptional ages and the chronological and/or topographical appearance of epileptic discharges was evaluated. Subjects and Methods: Forty-two infants born with severe perinatal complications at Okayama University Hospital from 1997 to 2001 were included in the study. EEGs were recorded at least twice for each infant, with at least one EEG recorded before and one EEG recorded after the corrected age of 6 months. The subjects were divided into two groups, according to the gestational age at birth. Group A contained those born at <34 weeks of gestation, and group B contained those born at >34 weeks of gestation. Results: Twenty-nine subjects were born at <34 weeks of gestational age and belonged to group A. The mean gestational age was 28.4 weeks. Twenty-three of them had extremely low birth weights of <1,000 g. The remaining 13 subjects belonged to group B, with birth weights ranging from 1,564 to 3,850 g (mean: 2,744.1 g). Infants in group B had various perinatal complications, including severe asphyxia, meningocele, and hemimegalencephaly. Nineteen of the 42 subjects (45.2%) had epileptic discharges during the follow-up period. Twelve of these 19 subjects evolved to West syndrome (63.2%), 4 had localization-related epilepsy (including 2 infants with hemimegalencephaly; 21.0%), and 3 showed transient EEG abnormalities (15.8%). The other 23 cases without epileptic discharges had no clinical seizures except 2 infants who had simple febrile convulsions. The initial epileptic discharges on EEGs were observed at postconceptional ages ranging from 36.1 to 97.7 weeks. Sixteen of the 19 cases had initial epileptic discharges before 65 weeks of postconceptional age. The localization of epileptic discharges was also investigated in 17 of 19 subjects whose first EEG findings were hypsarrhythmia. In 5 of 8 subjects (62.5%) with initial epileptic discharge before 50 weeks of postconceptional age, the epileptic discharges were observed in the frontal regions. In 7 of 9 subjects (77.8%) with initial epileptic discharge was after 50 weeks of postconceptional age, the epileptic discharges were located in the occipital regions. These topographical characteristics of the epileptic discharges were observed not only in infants who later developed West syndrome but also in infants who later developed localization-related epilepsy. However, 2 subjects with hemimegalencephaly had independent multifocal epileptic discharges at an extremely early stage of less than 40 weeks of postconceptional age. Of 12 subjects who later developed West syndrome, 10 subjects belonged to group A, and the remaining 2 subjects belonged to group B with hypoxic-ischemic encephalopathy due to severe asphyxia. Changes in epileptic discharges were also evaluated in all subjects with West syndrome. Focal cortical discharges appeared at ages ranging from 41 to 64 weeks postconception (mean: 52.0 weeks). These focal cortical discharges then changed to hypsarrhythmia at ages ranging from 51 to 82 weeks postconception (average: 63.4). These changes occurred irrespective of gestational age at birth and the age at onset of epileptic discharges. Conclusions: In the present study, the distribution of epileptic discharges in early infancy was related to postconceptional age. Evolution to hypsarrhythmia was also related to the postconceptional age of infants who developed West syndrome.