It is presumed that the EEG records only cerebral activity. However, frequently it can include other electrical activities, referred to as noise or artifact, which are not of cerebral origin. In the last few decades, evolution in digital technology has greatly improved the ability to record and display interpretable EEG. With the widespread availability of prolonged EEG recording, new artifacts have been described. The addition of concomitant video with audio during recordings has allowed in most instances to determine the source of certain artifacts. One of the challenges of interpreting EEGs consists of identifying artifacts correctly. Some of the EEG artifacts are so distinctive in appearance that the experienced reader can readily identify them. It is not uncommon for normal EEGs to be overinterpreted, especially by inexperienced readers. Failing to identify artifacts correctly can lead to “over reading” a study and doing so can result in misdiagnosis of epilepsy. This in turn can result in inappropriate treatments that ultimately can have serious clinical implications. This review will provide a description of the most commonly encountered artifacts that mimic spike or sharp waves, also referred to as interictal epileptiform discharges. In addition, we will describe troubleshooting approaches to eliminate these artifacts whenever possible. Artifacts that mimic ictal discharges will be reviewed in a different section.
Department of Neurology/Epilepsy Program, University of Kentucky, Lexington, Kentucky, U.S.A.
Address correspondence and reprint requests to Sally V. Mathias, MD, 740 South Limestone, St Kentucky Clinic, J 401 Lexington, KY 40536, U.S.A.; E-mail: email@example.com.
M. Bensalem-Owen reports receiving research grants from NeuroPace, GW Pharma and Sunovion for sponsored trials. The remaining author has no funding and conflicts of interest to disclose.