Febrile convulsions followed by nonfebrile convulsions. A clinical, electroencephalographic and follow-up study

103 patients with febrile convulsions followed by nonfebrile convulsions and 512 patients with febrile convulsions only (FC group) under 5 years of age at the first examination were analyzed from many aspects. A trimodal curve in distribution by age at onset of nonfebrile convulsions was seen: 2--3 years of age with occasional grand mal, 5--6 years of age with absence, and 12 years of age with awakening grand mal. Specific EEG abnormality was observed in 40% at the first examination (29% in FC group). Typical or atypical spike-and-wave complex, polyspikes, or continuous EEG abnormality were characteristic (slow wave burst with spike for FC group). Development from febrile convulsions into nonfebrile convulsions was detected in 17% among male and female patients. To identify an effective sign for the prediction of this development, the ratio between correct and incorrect prediction rates was analyzed. Specific paroxysmal EEG abnormality was increased over 3 years of age. EEG change due to aging and the significance of EEG reexamination were indicated.