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What Is a Seizure Focus?

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Issues in Clinical Epileptology: A View from the Bench

Part of the book series: Advances in Experimental Medicine and Biology ((AEMB,volume 813))

Abstract

The seizure focus is the site in the brain from which the seizure originated and is most likely equivalent to the epileptogenic zone, defined as the area of cerebral cortex indispensable for the generation of clinical seizures. The boundaries of this region cannot be defined at present by any diagnostic test. Imaging and EEG recording can define regions of functional deficit during the interictal period, regions that generate interictal spikes, regions responsible for the ictal symptoms, regions from which the seizure is triggered, and regions of structural damage. However, these regions define the epileptogenic zone only when they are spatially concordant. The frequent discrepancies suggest the essential involvement of synaptically connected regions, that is a distributive focus, in the origination of most seizures. Here we review supporting evidence from animal studies and studies of persons undergoing surgical resection for medically-intractable epilepsy. We conclude that very few of the common seizures are truly local, but rather depend on nodal interactions that permit spontaneous network excitability and behavioral expression. Recognition of the distributive focus underlying most seizures has motivated many surgical programs to upgrade their intracranial studies to capture activity in as much of the network as possible.

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Acknowledgment

We wish to acknowledge the unparalleled leadership provided by Phil Schwartzkroin in support of basic epilepsy research. His work on the relationship between seizures and synaptic inhibition strongly influenced the search for mechanisms of epileptogenesis in the animal models that emerged during the same period and the subsequent studies pursued in his laboratory taught us a great deal about both the normal and pathological functions of the hippocampus. We have profited enormously from Phil’s promotion of basic research through the American Epilepsy Society, including a term as president, his editorship of Epilepsia, his organizing numerous symposia, conferences, and books, and his exemplary training of outstanding young basic and translational neuroscientists.

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Authors and Affiliations

  1. Department of Pharmacology and Cancer Biology, Duke University Medical Center, 3813, Durham, NC, 27710, USA

    J. Victor Nadler

  2. Department of Neurosurgery, Yale University School of Medicine, 208082, New Haven, CT, 06520, USA

    Dennis D. Spencer

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  1. J. Victor Nadler
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  2. Dennis D. Spencer
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Correspondence to J. Victor Nadler .

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Editors and Affiliations

  1. Dept. of Child & Adoles. Psych., Phys. & Neurosc., and Psych., New York Univ. Langone Med. Ctr., Orangeburg, New York, USA

    Helen E. Scharfman

  2. Dept. of Comp. Med. and Neurol. & Neurol. Scs., Stanford University, Stanford, California, USA

    Paul S. Buckmaster

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Nadler, J.V., Spencer, D.D. (2014). What Is a Seizure Focus?. In: Scharfman, H., Buckmaster, P. (eds) Issues in Clinical Epileptology: A View from the Bench. Advances in Experimental Medicine and Biology, vol 813. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-8914-1_4

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  • DOI: https://doi.org/10.1007/978-94-017-8914-1_4

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  • Publisher Name: Springer, Dordrecht

  • Print ISBN: 978-94-017-8913-4

  • Online ISBN: 978-94-017-8914-1

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