Devising a Simplified System for Scalp EEG Classification and Reporting

Background: A standardized system for electroencephalography (EEG) reporting is important for guiding clinical decisions and for research purposes. The Mayo Clinic system developed in the late 90s is one of the most widely used classification systems. However, it has its flaws in view of which, an easier and more practical reporting system is the need of the hour. This should be simple but pragmatic, and for all practical purposes should be able to encompass the various epileptiform and nonepileptiform abnormalities in scalp EEG. Objectives: To devise a simplified system for scalp EEG reporting, which can be widely used as a simple tool to classify the various abnormalities in EEG to aid in diagnosis, prognostication, and research. Methods: We analyzed all the scalp EEGs performed in adults in our referral center from January 2000 to December 2025 ( n = 75,654). The EEGs which were reported as per the Mayo reporting system were all individually reanalyzed. Note that 16,842 EEGs were classified as Dys I, 18,904 were classified as Dys II, and 12,422 as Dys III. Delta grade 1 was noted in 27,959, grade 2 in 822, and grade 3 in 807. Benign variants were recorded in 13,268 EEGs. Among the nonepileptic events recorded were 2,964 psychogenic nonepileptic seizures, 432 syncope, and 246 sleep-related phenomenon. After studying the shortcomings and complexity of the Mayo system from the above EEGs, we propose a new system to report scalp EEG. Results: As per our proposed system, we classify scalp EEGs in both awake and sleep as follows (to combat the various flaws in the available classifications): (A) Level 1: definitely epileptiform activity including spikes, sharps, TIRDA (temporal intermittent rhythmic delta activity), PEDs (periodic epileptiform discharges) electrographic seizures, NCSE (nonconvulsive status epilepticus), and clinical seizures with EEG correlate (B) Level 2: slowing, asymmetry, suppression (C) Level 3: benign variants and nonepileptiform transients Conclusion: This new reporting system is more pragmatic, can be employed easily to report scalp EEGs, and is self-descriptive. Publication History Article published online: 15 July 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) Thieme Medical and Scientific Publishers Private Limited A-13A, Graphix Tower 1, 6th floor, Sector 62, Noida 201309, Uttar Pradesh, India