<abstract xmlns="http://www.w3.org/1999/xhtml"><sec id="j_joepi-2016-0014_s_001"><h3>Introduction</h3><p>Numerous reviews of the currently established concepts, strategies and diagnostic tools used in epilepsy surgery have been published. The focus concept which was initially developed by Forster, Penfield and Jasper and popularised and enriched by Lüders, is still fundamental for epilepsy surgery.</p></sec><sec id="j_joepi-2016-0014_s_002"><h3>Aim</h3><p>To present different conceptual views of the focus concept and to discuss more recent network hypothesis, emphasizing so-called “critical modes of an epileptogenic circuit”.</p></sec><sec id="j_joepi-2016-0014_s_003"><h3>Method</h3><p>A literature search was conducted using keywords: presurgical evaluation, epileptic focus concepts, cortical zones, diagnostic tools.</p></sec><sec id="j_joepi-2016-0014_s_004"><h3>Review and remarks</h3><p>The theoretical concepts of the epileptic focus are opposed to the network hypothesis. The definitions of the various cortical zones have been conceptualized in the presurgical evaluation of candidates for epilepsy surgery: the seizure onset zone versus the epileptogenic zone, the symptomatogenic zone, the irritative and functional deficit zones are characterized. The epileptogenic lesion, the “eloquent cortex” and secondary epileptogenesis (mirror focus) are dealt with. The current diagnostic techniques used in the definition of these cortical zones, such as video-EEG monitoring, non-invasive and invasive EEG recording techniques, magnetic resonance imaging, ictal single photon emission computed tomography, and positron emission tomography, are discussed and illustrated. Potential modern surrogate markers of epileptogenicity, such as <italic>High frequency oscillations, Ictal slow waves/DC shifts, Magnetic resonance spectroscopy, Functional MRI,</italic> the use of <italic>Magnetized nanoparticles</italic> in MRI, <italic>Transcranial magnetic stimulation, Optical intrinsic signal</italic> imaging, and <italic>Seizure prediction</italic> are discussed. Particular emphasis is put on the EEG: Scalp EEG, semi-invasive and invasive EEG (Stereoelectroencephalography) and intraoperative electrocorticography are illustrated. Ictal SPECT and <sup>18</sup>F-FDG PET are very helpful and several other procedures, such as dipole source localization and spike-triggered functional MRI are already widely used. The most important lateralizing and localizing ictal signs and symptoms are summarized. It is anticipated that the other clinically valid surrogate markers of epileptogenesis and epileptogenicity will be further developed in the near future. Until then the concordance of the results of seizure semiology, localization of epileptogenicity by EEG and MRI remains the most important prerequisite for successful epilepsy surgery.</p></sec><sec id="j_joepi-2016-0014_s_005"><h3>Conclusions and future perspectives</h3><p>Resective epilepsy surgery is a widely accepted and successful therapeutic approach, rendering up to 80% of selected patients seizure free. Although other therapies, such as radiosurgery, and responsive neurostimulation will increasingly play a role in patients with an unresectable lesion, it is unlikely that they will replace selective resective surgery. The hope is that new diagnostic techniques will be developed that permit more direct definition and measurement of the epileptogenic zone.</p></sec></abstract>

IntroductionNumerous reviews of the currently established concepts, strategies and diagnostic tools used in epilepsy surgery have been published. The focus concept which was initially developed by Forster, Penfield and Jasper and popularised and enriched by Lüders, is still fundamental for epilepsy surgery.AimTo present different conceptual views of the focus concept and to discuss more recent network hypothesis, emphasizing so-called “critical modes of an epileptogenic circuit”.MethodA literature search was conducted using keywords: presurgical evaluation, epileptic focus concepts, cortical zones, diagnostic tools.Review and remarksThe theoretical concepts of the epileptic focus are opposed to the network hypothesis. The definitions of the various cortical zones have been conceptualized in the presurgical evaluation of candidates for epilepsy surgery: the seizure onset zone versus the epileptogenic zone, the symptomatogenic zone, the irritative and functional deficit zones are characterized. The epileptogenic lesion, the “eloquent cortex” and secondary epileptogenesis (mirror focus) are dealt with. The current diagnostic techniques used in the definition of these cortical zones, such as video-EEG monitoring, non-invasive and invasive EEG recording techniques, magnetic resonance imaging, ictal single photon emission computed tomography, and positron emission tomography, are discussed and illustrated. Potential modern surrogate markers of epileptogenicity, such as High frequency oscillations, Ictal slow waves/DC shifts, Magnetic resonance spectroscopy, Functional MRI, the use of Magnetized nanoparticles in MRI, Transcranial magnetic stimulation, Optical intrinsic signal imaging, and Seizure prediction are discussed. Particular emphasis is put on the EEG: Scalp EEG, semi-invasive and invasive EEG (Stereoelectroencephalography) and intraoperative electrocorticography are illustrated. Ictal SPECT and 18F-FDG PET are very helpful and several other procedures, such as dipole source localization and spike-triggered functional MRI are already widely used. The most important lateralizing and localizing ictal signs and symptoms are summarized. It is anticipated that the other clinically valid surrogate markers of epileptogenesis and epileptogenicity will be further developed in the near future. Until then the concordance of the results of seizure semiology, localization of epileptogenicity by EEG and MRI remains the most important prerequisite for successful epilepsy surgery.Conclusions and future perspectivesResective epilepsy surgery is a widely accepted and successful therapeutic approach, rendering up to 80% of selected patients seizure free. Although other therapies, such as radiosurgery, and responsive neurostimulation will increasingly play a role in patients with an unresectable lesion, it is unlikely that they will replace selective resective surgery. The hope is that new diagnostic techniques will be developed that permit more direct definition and measurement of the epileptogenic zone.

Presurgical diagnosis of epilepsies – concepts and diagnostic tools

Journal of Epileptology

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

{"article-title":"Presurgical diagnosis of epilepsies \u2013 concepts and diagnostic tools"}

IntroductionNumerous reviews of the currently established concepts, strategies and diagnostic tools used in epilepsy surgery have been published. The focus...

Presurgical diagnosis of epilepsies – concepts and diagnostic tools

Publicado en línea: 22 dic 2016

Páginas: 115 - 140

Recibido: 11 nov 2016

Aceptado: 13 nov 2016

DOI: https://doi.org/10.21307/joepi-2016-0014

Palabras clave
presurgical evaluation, epileptic focus concept, cortical zones, diagnostic tools

© 2016 Heinz Gregor Wieser et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Presurgical diagnosis of epilepsies – concepts and diagnostic tools

Publicado en línea: 22 dic 2016

Páginas: 115 - 140

Recibido: 11 nov 2016

Aceptado: 13 nov 2016

DOI: https://doi.org/10.21307/joepi-2016-0014

Palabras clavepresurgical evaluation, epileptic focus concept, cortical zones, diagnostic tools

© 2016 Heinz Gregor Wieser et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Palabras clave
presurgical evaluation, epileptic focus concept, cortical zones, diagnostic tools