EEG in seizure prognosis: association of slow wave activity and other factors in patients with apparent misleading epileptiform findings.

Our previous study showed that patients with many spikes in their EEGs generally have uncontrolled seizures and those with no or rare spikes have controlled attacks. However, exceptions do exist, and this study was designed to determine what other aspects in the EEG could lead to the proper prognosis with these exceptions, rather than to an incorrect one. Two groups were assembled: 150 patients with 674 EEGs with controlled seizures and 150 patients with 804 EEGs with uncontrolled attacks. Our data showed that the presence or absence of a slow wave abnormality usually led to a proper prognosis in these exceptional cases. The absence of any slow wave abnormality, but with many spikes was usually associated with controlled attacks and the presence of slowing, especially with delta slow waves, but without spikes, was more often seen in patients with uncontrolled attacks. The change in the number of spikes over time also led to a more accurate prognosis.