ASYMMETRIC HYPSARRHYTHMIA - CLINICAL ELECTROENCEPHALOGRAPHIC AND RADIOLOGICAL FINDINGS

Twenty-six children (16 boys and 10 girls) with hypsarrhythmia and inf antile spasms (IS) were studied at the University of Michigan EEG Labo ratory in a 4-year period. Six (2 boys, 4 girls), had asymmetric hypsa rrhythmia with a preponderance of both slowing and epileptiform activi ty over one hemisphere. All 6 had the symptomatic form of IS, 4 with d ysplastic conditions, 1 with porencephaly from a cerebral infarct, and 1 with hypoxic-ischemic encephalopathy. Five children had focal abnor malities on either physical examination or imaging studies. Four had t he highest amplitude slowing and most epileptiform activity ipsilatera l to the lesion, in 1, it was contralateral. Asymmetric hypsarrhythmia constituted 23% of cases with hypsarrhythmia examined at our EEG labo ratory. The significant success in surgical therapy for some children with IS indicates the importance of identifying focal hemispheric abno rmalities even if they are not apparent clinically. EEG may suggest fo cal changes not detected clinically or radiologically.