Ingmar Blümcke, Harry V Vinters, Dawna Armstrong, Eleonora Aronica, Maria Thom, Roberto Spreafico
become a successful treatment option for many of these patients. A broad spectrum of malformations of cortical development (MCD) can be histopathologically identified in resective surgical brain samples. Here, we discuss neuropathological findings and available classification systems in children and adult patients. Particular emphasis will be paid to the classification system for focal cortical dysplasias (FCD), which can be histopathologically distinguished as type I and II. Also mild forms of cortical malformations (mMCD) may be present, including heterotopic neurons in white matter location. However, different cohorts of epilepsy patients may present with similar histopathological findings and clinico-pathological correlations are not always comparable with respect to outcome prediction. We will, therefore, discuss also the difficulties to classify some FCD variants. Notwithstanding, the underlying pathomechanisms in all FCD entities need to be specified. A comprehensive approach taking all currently available data into consideration will be mandatory to further develop our current understanding of FCDs, and to continuously improve our concept for a reliable classification system.
Nadia Colombo, Noriko Salamon, Charles Raybaud, Çigdem Özkara, A James Barkovich
zones, neuronal migration and cortical organization. With the improvement and increased utilization of modern imaging techniques, MCD have been increasingly recognized as a major cause of seizure disorders. The advent of Magnetic Resonance Imaging (MRI), in particular, has revolutionized the investigation and the treatment of patients with epilepsy. High-resolution MRI may elucidate the type, the extension and the localization of MCD; therefore, in a group of patients suffering from drug-resistant partial epilepsy (DRPE), MRI greatly contributes to the identification of subjects who are suitable for surgical treatment. In the recent past, many efforts were addressed to establish the MRI diagnostic criteria for a peculiar group of MCD, namely focal cortical dysplasias (FCD), histopathologically distinguished as types I and II. Some subtle FCD, which were previously cryptic to imaging investigation, can now be recognized by MRI, however their detection and specification remains challenging. This review will re-visit the neuroimaging findings, including structural MRI, PET, co-registered PET/MRI, MEG and diffusion tensor imaging (DTI) of FCD types I and II. Three major issues will be discussed: 1) the morphological MRI features of the FCDs, 2) the utility of PET and MEG and the use of co-registration methods and 3) diffusion tensor imaging (DTI) as a future modality of investigation, which may add additional informations regarding the microstructure of the grey matter (GM) and white matter (WM) in cortical dysplasia.
Giorgio Battaglia, Albert J Becker, Joseph LoTurco, Alfonso Represa, Scott C Baraban, Steven N Roper, Annamaria Vezzani
frequently gangliogliomas. The neuropathological findings are variable but suggest aberrant proliferation, migration, and differentiation of neural precursor cells as essential pathogenetic elements. Recent advances in animal models for MCDs allow new insights in the molecular pathogenesis of these epilepsy-associated lesions. Novel approaches, presented here, comprise RNA interference strategies to generate and study experimental models of subcortical band heterotopia and study functional aspects of aberrantly shaped and positioned neurons. Exciting analyses address impaired NMDA receptor expression in FCD animal models compared to human FCDs and excitatory imbalances in MCD animal models such as lissencephaly gene ablated mice as well as in utero irradiated rats. An improved understanding of relevant pathomechanisms will advance the development of targeted treatment strategies for epilepsy-associated malformations.