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Malformations of Cortical Development and Aberrant Cortical Networks: Epileptogenesis and Functional Organization

Guerrini, Renzo*; Barba, Carmen*†

Journal of Clinical Neurophysiology: December 2010 - Volume 27 - Issue 6 - p 372-379
doi: 10.1097/WNP.0b013e3181fe0585
Invited Review
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Malformations of cortical development are a major cause of drug-resistant epilepsy. Focal cortical dysplasia, heterotopia, and polymicrogyria are often manifested as discrete areas of abnormal neuronal migration and improper development of the cerebral cortex. Some of the patients harboring these malformations have obvious neurologic impairment, but others show unexpected deficits that are detectable only by screening. The role of surgical treatment of epilepsy due to localized malformations of cortical development is now established. However, its technical application can be challenging in that localization of function based on anatomic landmarks may not be reliable. Intracranial recordings have shown a high propensity for complex epileptogenic networks that may include remote cortical and subcortical regions. The MRI visible area of cortical abnormality should therefore be regarded as just an indicator of the epileptogenic zone rather than its tangible substrate. Completeness of resection, after delineation of the ictal onset zone, a key factor for successful epilepsy surgery, may be particularly difficult, and invasive EEG monitoring is necessary in most patients. Neural plasticity issues are of primary importance to surgical planning as the possibility of removing eloquent cortex permits more complete procedures with potentially higher rates of success. However, the functional consequences of malformative lesions are still poorly understood; conservation of function in the dysplastic cortex, its atypical representation, and relocation outside the malformed area are all possible. Surgical planning for associated epilepsy should therefore be based on individual assessments of structural imaging and of the major functions relevant to the area in question in the individual patient.

From the *Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Firenze; and †IRCCS Stella Maris, Pisa, Italy.

Address correspondence and reprint requests to Renzo Guerrini, Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, viale Pieraccini 24, 50139, Firenze, Italy; e-mail: r.guerrini@meyer.it.

Copyright © 2010 American Clinical Neurophysiology Society