The importance of interictal epileptiform abnormalities discovered with cassette electroencephalographic (EEG) monitoring has been assessed in a group of 184 nonepileptic patients referred because of headache and reported from the Department of Neurology, Yale University School of Medicine, New Haven, CT; and the Neurology Service, Veterans Administration Medical Center, West Haven, CT. Only one (0.5%) of these patients had epileptiform abnormalities on cassette EEG and the incidence was no higher than on routine EEG. In contrast, the authors have found more than 50% of episodes characterized as seizures to be accompanied by cassette EEG seizure activity. Consequently, the detection of such abnormalities seems a worthwhile aspect of cassette EEG interpretation when the goal of monitoring is the detection of evidence to support a diagnosis of epilepsy. 
COMMENT. The mean age of patients reporting headache in this study was 30 years, and only five patients were age 10 years or less. The incidence of epileptiform activity may well be higher in a group of children with headache.