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New horizons in clinical electric source imaging

Neue Perspektiven in der klinischen EEG-Quellenlokalisation

Abstract

The clinical usefulness of electric source imaging (ESI) in presurgical epilepsy evaluation has now been demonstrated; however, its use in clinical routine remains somewhat limited. Here, we discuss the added clinical value of ESI and how its integration in the presurgical work-up of epilepsy patients can be optimized. We present methodological differences of ESI on interictal and ictal epileptic activity as well as their evaluation compared with intracranial EEG data. Beyond the choice of patterns used for ESI, the choice of inverse methods can have tremendous impact on source imaging results. It is of great clinical interest that during recent years several inverse methods have been developed that are sensitive to the spatial extent of the generators of epileptic activity. In this regard, we discuss the performance of different approaches. Advanced inverse methods that consider the temporal evolution of the EEG signal even allow for localizing deep generators with good spatial accuracy. In summary, recent methodological advances in ESI foster its application in clinical practice.

Zusammenfassung

Der Nutzen der Elektroenzephalogramm(EEG)-Quellenlokalisation („electric source imaging“, ESI) in der prächirurgischen Epilepsiediagnostik ist belegt, klinisch wird ESI allerdings weiterhin nur begrenzt eingesetzt. Innerhalb dieses Artikels werden Vorteile der ESI und ihre Integration in den klinischen Alltag vorgestellt. Es werden methodische Unterschiede zwischen ESI auf der Basis interiktaler und iktaler epileptischer Aktivität und die Validierung mit dem intrakraniellen EEG erörtert. Über die Auswahl der EEG-Muster hinaus kann die Wahl der inversen Methode entscheidenden Einfluss auf das ESI-Ergebnis haben. Von großem klinischem Interesse ist, dass in letzter Zeit inverse Methoden entwickelt wurden, die sensitiv für die Ausdehnung von Generatoren epileptischer Aktivität sind. In diesem Zusammenhang wird die Leistungsfähigkeit unterschiedlicher Methoden verglichen. Fortgeschrittene inverse Methoden sind zudem in der Lage, den zeitlichen Verlauf von EEG-Signalen zu berücksichtigen und auch von der Oberfläche weit entfernte, tiefe Generatoren epileptischer Aktivität mit guter räumlicher Auflösung zu lokalisieren. Zusammenfassend unterstützen neue methodische Entwicklungen die weitere klinische Anwendung von ESI.

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Acknowledgements

Laith Hamid acknowledges the support by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) through the Collaborative Research Center (Sonderforschungsbereich) SFB1261 “Magnetoelectric Electrodes: From Composite Materials to Biomagnetic Diagnostics” and the support by the European Union’s Seventh Framework Programme for research, technological development and demonstration through the project DESIRE “Development Epilepsy” (Grant Agreement no: 602531), WP2 & WP4, http://epilepsydesireproject.eu/. Pierre Mégevand acknowledges the support of the Swiss National Science Foundation (grant 167836).

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Correspondence to Pierre Mégevand MD, Ph.D. or Marcel Heers.

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P. Mégevand, L. Hamid, M. Dümpelmann, and M. Heers declare that they have no competing interests.

For this article no studies with human participants or animals were performed by any of the authors. All studies performed were in accordance with the ethical standards indicated in each case.

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Some of the methods reported in this article are not certified for clinical use yet.

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Mégevand, P., Hamid, L., Dümpelmann, M. et al. New horizons in clinical electric source imaging. Z. Epileptol. 32, 187–193 (2019). https://doi.org/10.1007/s10309-019-0258-6

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Keywords

  • Electric source imaging (ESI)
  • Epilepsy
  • Inverse methods
  • Epilepsy surgery

Schlüsselwörter

  • EEG-Quellenlokalisation
  • Epilepsie
  • Inverse Methoden
  • Epilepsiechirurgie