Intracranial Electrode Investigations in the Presurgical Evaluation of Drug-Resistant Epilepsy

  • Kyriakos Garganis


In the field of epilepsy surgery, intracranial electrode (ICE) studies can overcome several limitations of surface electroencephalograms (EEGs). To briefly summarize the most important of them:
  1. (a)

    Conduction of the brain’s electrical activity to surface electrodes is significantly hampered by the poor conductivity of the skull [1, 2]. Signals of particular interest (e.g., sharp waves) need to recruit at least a 10–15 square centimeter area of cortical surface in order to be detectable by surface electrodes [3]. Signals recruiting less than that are only recorded by exception. Contamination by muscle and other artifacts is another source of difficulty with signal detection and interpretation.

  2. (b)

    Initial fast-frequency components of the ictal epileptic discharge (particularly important for ictal-onset region localization) are also attenuated by the intervening layers between the cortex and the skull. An ictal EEG rhythm may be seen only after considerable propagation from the site of origin has taken place following recruitment of extensive cortical surface and evolution to synchronized, lower frequency activity [4, 5].

  3. (c)

    Signals from “hidden” brain regions at a distance from surface recording electrodes (especially from the interhemispheric fissure and basal and medial frontal regions) are also, barely, recorded [6, 7].



Epilepsy surgery Intracranial electroencephalography Medial temporal sclerosis Focal cortical dysplasia Brain tumors 


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2019

Authors and Affiliations

  • Kyriakos Garganis
    • 1
  1. 1.Epilepsy Center, St. Luke’s Hospital, Panorama-ThessalonikiThessalonikiGreece

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