Sunday July 2, 2006 9:30 - 11:30 Hall 1 Discussion Group Session Clinical neuropathology of epilepsy associated cortical malformations

Abstract

Abstract 1 A. Palmini ( 1 UZ Gasthuisberg, Leuven, Belgium and Porto Alegre Epilepsy Surgery Program, Porto Alegre, Brazil ) Furthering the knowledge about focal epilepsies will depend on a detailed understanding of the determinants of epileptogenicity, other functional properties, clinical and electrographic presentations, and imaging features of specific types of lesions. A crucial step in this direction is to precisely define the histopathological features of epileptogenic lesions. Interestingly, high resolution MRI has led to a puzzling scenario in which lesions are often identified and described in global, categorical terminology, distracting the attention to differences between specific types of lesions that present ‘roughly’ with the same imaging picture. This situation has been witnessed in relation to the identification and treatment of cortical malformations associated with epilepsy, particularly the focal dysplastic lesions. Therefore, an effort was made to develop a histopathological classification system for focal dysplastic lesions that could be correlated with imaging, clinical, neurophysiological, functional, surgical, and prognostic aspects. This classification proposes the clustering of minimal histopathological abnormalities that do not disrupt cortical architecture (such as small clusters of heterotopic neurons in the white matter) in a specific category, thus abandoning the terminology “microdysgenesis.” In addition, the classification distributes focal dysplastic lesions in which cortical dyslamination is a major feature along a continuum of histological abnormalities which in one end is represented by dyslamination only, and proceeds to more complex histopathological patterns characterized progressively by immature yet ‘nondysplastic’ cellular elements, dysplastic neurons, and, finally, in the opposite end, by lesions harboring dysplastic neurons and balloon cells. Several clinical studies incorporating this classification system have appeared in recent years, and have confirmed that specific histopathological types of focal dysplastic lesions are indeed associated with more or less specific imaging, neurophysiological, functional and prognostic features. Some of these studies will be presented in the symposium.