Spike EEG abnormalities in patients without epileptic seizures: a clinical and long-term follow-up study.

A study was conducted on a total of 850 patients who had not previously manifested any epileptic seizures but exhibited at least one spike EEG abnormality. They accounted for 7.2% of the total number of patients without epileptic seizures (850/11,773). Among the 850 patients, 564 were followed up for 1-24 years. Nine boys and one girl, i.e. 1.8% of the 564 patients, had manifested epileptic seizures during the observation period. They expressed the following six characteristics: males, first EEG examination at 0-4 years of age, onset of initial chief complaints at 0-6 years of age, mental retardation, spike and wave EEG abnormalities and past history of perinatal birth injuries. These factors are considered to be efficient in detecting patients liable to manifest epileptic seizures later.