Continuous EEG monitoring in a patient with massive carbamazepine overdose.

The authors report a woman who took a massive overdose (OD) of carbamazepine (CBZ). On admission she was unconscious with absent brainstem reflexes and multifocal stimulus-sensitive myoclonus. Continuous EEG recordings showed a burst-suppression pattern with bursts containing only generalized spikes accompanying myoclonic activity. Myoclonus and EEG bursts were both spontaneous and stimulus induced. With treatment, the serum CBZ concentration declined, and the EEG became more continuous and rhythmic without epileptiform discharges. Unfortunately, the patient died from adult respiratory distress syndrome. Autopsy revealed that cortical and subcortical structures were normal without neuronal necrosis or eosinophilia. Massive CBZ OD may produce a reversible encephalopathy that includes cortical hyperexcitability, a profound burst-suppression EEG pattern, and cranial nerve areflexia. Continuous EEG monitoring is helpful in managing seizures that occur as a complication of CBZ OD, after the course of recovery or worsening, and in providing assistance with prognosis.