Electroencephalography in clinical epilepsy research

Electroencephalography (EEG) remains central to the investigation of epilepsy. This review discusses two clinical problems at the temporal extremes of neurophysiologic recording: evaluation of the clinical significance of individual spike discharges in benign epilepsy of childhood with centrotemporal spikes (BECTS), and prolonged (several days) continuous EEG monitoring in the ICU. BECTS is misdiagnosed often, and probably mis-treated often as well. Though the long-term outcome is usually excellent, it remains unclear whether the individual epileptiform discharges have a clinical effect. Answering this question is difficult, in part because of the natural evolution of the epilepsy and its different appearance depending on wakefulness or sleep state, and also due to substantial methodologic problems in measuring short and long-term cognitive effects. Continuous EEG (CEEG) recording has grown remarkably over the last 10 years. It has proved crucial in the diagnosis of nonconvulsive status epilepticus (NCSE), especially in the ICU, given the usual lack of obvious clinical signs of seizures in most of these patients, many of whom are critically ill. Much progress has been made in agreeing on terminology for the EEG findings, but diagnosis is still complicated. More efficient and reliable technology is being developed to help process the massive amount of data captured by CEEG and make it more useful (and in a timely fashion) clinically. Still, it is not completely clear which patients should be monitored, for how long, and what is the best role for CEEG in assessing and adjusting treatment once the diagnosis has been made. Investigators are using CEEG to study “seizure burden,” to help determine what are the long-term effects of nonconvulsive seizures and NCSE, and to help guide treatment and improve outcome.