Estimating the importance of epileptiform abnormalities discovered on cassette electroencephalographic monitoring
S. L. Bridgers, P. B. Wade and J. S. Ebersole
Department of Neurology, Yale University School of Medicine, New Haven, Conn.
Assessment of the importance of interictal epileptiform abnormalities
discovered with cassette electroencephalographic (EEG) monitoring requires
some appreciation of the frequency with which such abnormalities may be
encountered in individuals without epilepsy. From a clinical experience
involving more than 2500 patients, we have defined a group of 184 patients
referred because of headache, with no additional referral information to
suggest seizures. Only one (0.5%) of these patients had epileptiform
abnormalities on cassette EEG, yielding 95% and 99% confidence limits for
the incidence of epileptiform abnormalities in the unselected nonepileptic
headache population of 1.5% and 1.8%. Presuming that the incidence of
cassette EEG epileptiform abnormalities in the healthy population would be
no higher than in this patient group, we suggest that epileptiform
abnormalities are no more likely to be incidental findings on cassette EEG
monitoring than on routine EEG. 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.