System reference electrode artifacts mimicking alpha coma and electrographic seizures in EEG

We are presenting a patient with frequent seizures who required an intensive care admission for intubation and ventilation. The patient was monitored with 24-hour EEG and video for clinical and subclinical seizures. Her EEG showed artifactual changes which initially were interpreted as electrographic seizures. Correction of the artifact revealed the actual background activities. The EEG technologist must be aware of such artifacts and correct them promptly to avoid unnecessary intervention with potential negative outcome for the patient.