We report an unusual cause of unresponsiveness in a 73-year-old woman seen in the emergency department. Extensive evaluation, including an emergency EEG that demonstrated rhythmic, high-voltage spike-and-wave discharges characteristic of convulsive activity, confirmed the diagnosis of generalized tonic status epilepticus. The patient's persistent subclinical seizures terminated after the IV administration of diazepam. Varying presentations of generalized tonic status epilepticus have been described in the neurology literature, with EEG confirmation of this diagnosis. Review of the emergency medicine literature does not describe a similar presentation of altered mental status in the adult population. This case illustrates one necessary role for ED EEG in the identification of occult status epilepticus causing altered mental status.