The electroencephalogram in epilepsy

In light of the considerable divergence of opinion among various investigators regarding the incidence of electroencephalographic abnormality in patients with convulsive disorders, the author made a study of his own records of 430 patients with a diagnosis of epilepsy. In 122 the seizures were symptomatic, in the remainder idiopathic, and the overall incidence of electroencephalographic abnormality was little different in the two groups. In the whole series 64.9 per cent showed abnormal tracings, while in those under 16 years of age the incidence was 71.8 per cent. The highest incidence was in patients in whom seizures had begun when they were between 10 and 15 years of age and in those with a duration of seizures from 5 to 10 years. Of patients with clinical petit mal, 76 per cent had abnormal records, but only 34.6 showed petit mal complexes. Lateralized or focal abnormality was three times as frequent in the symptomatic as in the idiopathic group.