Abstract
BackgroundFocal cortical dysplasias (FCD) are local disturbances of neocortical architecture and a common cause of pharmaco-resistant focal epilepsy. Little is known about the pathomechanisms leading to architectural abnormalities associated with FCD.ResultsIn the present study we compared 52 FCD cases originating from the frontal or temporal lobe with or without Ammon’s horn sclerosis (AHS) with regard to structural and molecular differences. We applied layer-specific (ER81, RORß, SMI32, TLE4) and interneuron (calbindin, parvalbumin) markers by means of immunohistochemistry, in situ hybridization (ISH), and real time RT-PCR and correlated our findings with clinical parameters. We found that: (1) Structural abnormalities were most prominent in layers III-VI including changed morphology of individual neurons or dispersion, blurring and thinning of layers. These alterations were most pronounced in isolated frontal FCD, whereas the most homogeneous group was FCD IIIa. (2) Numbers of calbindin- and parvalbumin-positive interneurons varied considerably within the different FCD groups, but were not generally reduced. A significant decrease was only found for calbindin-positive interneurons in frontal FCD, and for parvalbumin-positive interneurons in FCD IIIa. (3) Interestingly, FCD IIIa presented with significant changes in the numbers of calbindin- or TLE4-positive neurons when compared to isolated FCD or controls. (4) Correlations between clinical and cellular parameters strongly depended on FCD localisation and age of the patients.ConclusionsIn summary, our data suggest that late cortical development is disturbed in FCD, yet most likely by different causes depending on brain region, FCD type and FCD severity.
Highlights
Focal cortical dysplasias (FCD) are local disturbances of neocortical architecture and a common cause of pharmaco-resistant focal epilepsy
In summary, our data suggest that late cortical development is disturbed in FCD, yet most likely by different causes depending on brain region, FCD type and FCD severity
The recent FCD classification system proposed by the Task Force of the International League Against Epilepsy (ILAE) Diagnostic Commission [19] limits type I FCD to isolated lesions and introduces type III FCD for architectural dysplasia in combination with other principal lesions on the basis that the isolated forms may evolve during cortical development, whereas the others may be acquired as a result of the main epileptogenic lesion (i.e., Ammon’s horn sclerosis (AHS))
Summary
Focal cortical dysplasias (FCD) are local disturbances of neocortical architecture and a common cause of pharmaco-resistant focal epilepsy. The histological abnormalities in FCD with Balloon cells are more prominent than in FCD without Balloon cells, there is no difference regarding the severity of epilepsy [11,13,14,15] In both patient groups a high seizure frequency and a pharmaco-resistant course of the disease is common [16,17,18]. The recent FCD classification system proposed by the Task Force of the International League Against Epilepsy (ILAE) Diagnostic Commission [19] limits type I FCD to isolated lesions and introduces type III FCD for architectural dysplasia in combination with other principal lesions (type IIIa when associated with AHS) on the basis that the isolated forms may evolve during cortical development, whereas the others may be acquired as a result of the main epileptogenic lesion (i.e., AHS)
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