Recognizing physiological rhythms and biological artefacts on stereo-EEG

OBJECTIVES: Stereoelectroencephalography (stereo-EEG, SEEG) provides macro-electrode electroencephalography recordings of intracerebral activity in different brain regions in the context of presurgical evaluation of drug-resistant focal epilepsy. Accurate interpretation of SEEG signals is critical for correctly identifying the epileptogenic zone and guiding surgical strategy. Learning to recognize commonly occurring physiological activity and biological artefacts is important to confidently distinguish these from pathologic activities. This educational article aims to provide selected illustrative examples of common intracerebral physiological rhythms and biological artefacts, for clinicians and neurophysiology technologists learning to interpret SEEG. METHODS: We reviewed scalp-EEG and SEEG data from adult patients who underwent SEEG implantation at the Mater Epilepsy Unit in Brisbane, Australia. Representative examples of physiological rhythms on SEEG were selected. Quantified signal analysis was performed on selected samples. RESULTS: Representative examples of wake and sleep physiological rhythms on SEEG including posterior dominant alpha rhythm, mu rhythm, physiologic gamma, lambda waves, sleep spindles and K-complexes are provided. Photic driving responses and common biological artefacts (muscle artefact, chewing) are also illustrated. CONCLUSION: By integrating electrophysiological morphology with anatomical localization and functional context, this educational article aims to support clinicians and researchers in learning to distinguish physiological rhythms and biological artefacts from pathological activity. Acquiring a solid understanding of normal SEEG electrophysiological patterns is essential for accurate interpretation, reliable presurgical evaluation, and a more comprehensive understanding of brain electrophysiology.