The prognostic significance of diazepam-induced EEG changes in epilepsy: a follow-up study.

Diazepam (0.1-0.3 mg/kg) was injected intravenously, its effect on scalp EEG was evaluated visually and by computer in 84 cases of epilepsy, and long-term follow-up was carried out in an attempt to explore relationships between the EEG changes produced by diazepam and the prognosis in these patients. The average length of follow-up was 3 years (range 2-3.5) in 48 out of 84 cases (57%). The EEG visually responded to diazepam (abolition of abnormal activity with emergence of fast activity) in 33/48 cases. Subsequent follow-up showed that 29 (88%) of these had a good prognosis (seizure-free or a 50% or more reduction in seizures) and 4 others (12%) had a poor result (frequency of seizures increased, unchanged or decreased less than 50%). Fifteen patients had a negative EEG response to the drug, 4 (27%) of whom had a favorable outcome and 11 (73%) an unfavorable result. These results were statistically significant. The percentage of diazepam-induced EEG changes in beta activity (PDICB) was also significantly positively related to the percentage of reduction in seizure frequency in these patients (r = 0.55, p < 0.001). In 79% of patients with PDICB values more than 2, and 30% of those with values less than 2, a good outcome occurred whereas 21% and 70%, respectively, had a poor outcome (p < 0.001). These results showed that the patterns of EEG change induced by diazepam are intimately related to the outcome of epilepsy.