Value of the early electroencephalogram after a first unprovoked seizure

Studies on the predictive value of the electroencephalogram (EEG) concerning the risk of seizure recurrence have shown contradictory results. We prospectively studied the predictive value of the standard EEG and EEG with sleep deprivation for seizure relapse in adult patients presenting with a first unprovoked seizure. EEGs were performed on 157 adult patients within the first 48 hours of the first seizure. Additional EEGs with sleep deprivation were obtained in 60 cases. The standard EEG was abnormal in 70.7% and significantly associated with an increased risk of seizure recurrence [risk ratio 4.5, 95% confidence interval (CI) 1.8; 11.3, p=0.001]. Subgroup analysis revealed the highest recurrence rates for patients with focal epileptiform activity (risk ratio 2.2, CI 1.2; 4.2, p=0.01). EEGs with sleep deprivation were abnormal in 48.3% of all cases and revealed epileptiform discharges in 13.3% of the patients who had no epileptiform activity in the standard EEG. Routine EEG revealed abnormalities in 60 of 94 patients who presented with normal neurologic status on admission. Further neuroradiological examinations detected previously unknown brain lesions in 19 of these cases, particularly cerebrovascular disease (CVD, n=7), brain tumors (n=6), and posttraumatic scars (n=4). In conclusion, the EEG is important for the early detection of focal nonepileptic and epileptic abnormalities after a first unprovoked seizure in adult patients and may provide valuable information on previously unknown disorders, particularly CVD and cerebral tumors. The abnormal EEG is a highly significant predictor for seizure recurrence. An additional EEG with sleep deprivation is helpful in cases when standard EEG does not reveal epileptiform discharges.