Clinical And Basic Research For Epileptogenic Cortical Dysplastic Lesions

Malformations of cortical development (MCDs) are brain malformations that result from abnormalities affecting the normal processes of cortical development and involving cells that participate in formation of the cerebral cortex under normal circumstances. It is not surprising, therefore, that MCDs are often associated with recurrent seizures, and that these seizures always be difficult controlled with medication. Since the term "focal cortical dysplasia" (FCD) was first used by Taylor in 1971 to describe a histological abnormality seen in surgical specimens from 10 patients with epilepsy, the MCDs gradually gained widespread attention in neuroscience workers. As the widespread clinical application of magnetic resonance image (MRI) in 90s last century, varies subtypes of MCDs became the second large category of epilepsy related surgery. The clinical and basic investigations for MCDs are becoming the "hot spot" in epilepsy research.The most commonest subtypes of MCDs be confronted with epilepsy surgery include tuberous sclerosis, FCD, hemimegalencephaly, dysembryoplastic neuroepithelial tumor, ganglioglioma and gangliocytoma. Although great improvement had been achieved in the last two decades, there are still lots of questions about the semiology, nuroimage, electrophysiology, molecular biology and surgical treatment need to be answered.In this research, we studied the clinical feature, structural imaging, metabolic imaging and pathological characteristics of FCDs with retrospective analysis method, and studied the MR- pathologic correlationn and long-term follow up results of different subtypes of FCD. Retrospective analysis of neuroimage, surgical approach, treatment options and prognosis about dysembryoplastic neuroepithelial tumor were proceeded. The gene expression differences in FCDⅡb type cortical dysplasia, dysembryoplastic neuroepithelial tumor simple type and ganglioglioma (WHOⅠ) were studied with gene microarray methods. The main content of this article are summarized as follows.Part 1 Background for researchMalformations of cortical development (MCDs) and their classification, common dysplastic lesions related to epilepsy surgery, and recent problems are briefly reviewed.MCDs are brain malformations that result from abnormalities affecting the normal processes of cortical development and involving cells that participate in formation of the cerebral cortex under normal circumstances. It is not surprising therefore that MCDs are often associated with recurrent seizures, always be difficult controlled with medication. The precise incidence of MCDs is not known. It is estimated that 3% of all epilepsy patients and 25～40% of intractable or medication-resistant childhood epilepsy are attributable to MCDs, and that at least 75% of patients with MCDs will have epilepsy. Now, the MCDs are the second largest group just less than hippocampal sclerosis in epilepsy surgery candidates.There are several classification systems for MCDs. The classification scheme published by Barkovich et al in 1996 was accepted in worldwide, which includes four categories as below:1 malformations due to abnormal neuronal and glial proliferation or apoptosis; 2 malformations due to abnormal neuronal migration; 3 malformations due to abnormal cortical organization (such as late neuronal migration); 4 MCDs with no otherwise classified. Each category is re-divided in several subtypes further. The most common subtypes of MCDs in epilepsy surgery including focal cortical dysplasia, tuberous sclerosis complex, dysembryoplastic neuroepithelial tumor, ganglioglioma and gangliocytoma.Part 2 The semiology, structural imaging, metabolic imaging and the surgical outcome in different subtypes of focal cortical dysplasia (FCDs)ObjectiveTo explore the imaging characteristics and long-term outcome after epilepsy surgery of epileptogenic focal cortical dysplasia (FCD).Material and MethodsTwenty nine cases of FCDs confirmed by pathology were retrospectively analyzed. The preoperative evaluation included ictal symptom, MRI, scalp EEG and PET. Epileptogenic foci resection was applied with intra-operative EEG monitoring in all 29 cases,12 cases of which were under awaking craniotomy, anterior temporal lobectomy was applied in 8 cases which had accompanied hippocampal sclerosis. Datas are analyzed by SPSS13.0 software packet, and using t-test and x2 inspection. A value of p< 0.05 was considered statistically significant.ResultsThere are no statistics difference in ictal semiology, family history and past history in different subtypes of FCDs. The age of seizure onset (P<0.05) and the age of operation (P<0.001) are earlier in FCDⅠthan FCDⅡ. According to Palmini classification, pathology results confirmed FCDⅡb in 13 cases, FCDⅡa in 11 cases, FCDⅠb in 3 cases and FCDⅠa in 2 cases respectively.The characteristics of MR image included blurring of gray-white matter junction (23 cases), gray matter thickening (23 cases), blurring of fiber tracts connecting adjacent gyri (U-fibers) (23 cases) and increased signal intensity on T2 or Flair sequence (13case). All of them above are belong to the characteristics of FCDⅡb. PET scan was applied in 26 cases,24 of which were found as the decreased glucose metabolism.The follow-up period was 15～53 months, mean as 31 months. EagelⅠachieved in 21 (72.4%), EagelⅡin 6 (20.7%) and EagelⅢin 2 (6.9%) of all cases respectively. EagelⅠachieved in 9 of 11(81.8%) of FCDⅡa. EagelⅠachieved in 11 of 13(84.6%) of FCDⅡa. EagelⅡ(50%)and EagelⅢ(50%)were achieved in each of the 2 FCD la cases. EagelⅠ(33.3%), EagelⅡ(33.3%) and EagelⅢ(33%) were achieved in each of the 3 FCD Ib cases. The seizure control rate was favorable (P<0.005) in FCDⅡ(EagelⅠin 20 of 24cases,83.3%) than in FCDⅠ(EagelⅠin 1 of 5cases,20%). The seizure control rate was much more favorable (P<0.05) in FCDs located in temporal lobe group (EagelⅠin 15 of 17cases, 88.2%) than in no-temporal group (EagelⅠin 6 of 12cases,50%). EagelⅠachieved in 10 of 12 cases (83%) in the awaking craniotomy group and 11 of 17 cases (64.7%) in conventional surgery group. EagelⅠachieved in 7 of 8 cases (87.5%) in the dual-pathology group and 14 of 21 cases (66.7%) in non-dual-pathology group, the result of which had no significance for statistics.Temporary paralysis occurred in 3 patients, and 2 of them recovered in 3～6 months. Mild motor aphasia occurred in 1 patient case and gradually returned to normal level in 6 weeks. There was no mortality.Conclusion1 The blurring of fiber tracts connecting adjacent gyri (U-fibers) on MR image are sensitive evidence for the diagnosis of FCD;2 Increased signal intensity on T2 and Flair sequence are reliable evidence for the diagnosis of FCDⅡb;3 The seizure control rate is more favorable in FCDs located in temporal lobe group than in extra- temporal group;4 The surgical results in the dual-pathology group and non- dual-pathology group have no significance for statistics;5 The seizure control rate is more favorable in FCDⅡgroup than in FCDⅠgroup;6 PET scan contributes to preoperative diagnosis of FCDs;7 Epileptogenic foci resection with awaking craniotomy technique is superior to conventional surgery for higher seizure control rate.Part 3 Neuroimaging characteristics and treatment option for dysembryo-plastic neuroepithelial tumorObjectiveTo explore the clinical manifestations, neuroimage, treatment and surgical outcome of dysembryoplastic neuroepithelial tumor(DNET).Materials and MethodsThe semiology, neuroimage, pathological data and follow-up results of 10 postoperative and 3 suspected cases of dysembryoplastic neuroepithelial tumor were retrospectively analyzed. Preoperative evaluation included symptom study, MRI, EEG and PET. Epileptogenic foci resection was applied with intra-operative EEG monitoring in all 10 cases. Total lesion resection and the extended lesion resection were achieved in 9 patients, and "partial resection+dis-connection" in 1 case. Awaking craniotomy technique was applied in 5 cases. Three of suspected cases just were treated with antiepileptic drugs (AEDs) and follow-up. ResultsMagnetic resonance (MR) scan were performed in all 13 patients. The features of MR image included as below. The cortex was involved in all 13 cases. The lesions looked like triangle in 5 (38.46%), square-like in 5 (38.46%) and irregular shape in 3 (23.07%) cases respectively. The lesion had decreased signal intensity on T1 sequence in 3 (23.08%) cases, and iso-signal intensity on T1 sequence in 10 (76.92%) cases. All of 13 cases (100%) had increased signal intensity on T2 and the Flair sequence. MR scans disclosed pseudocyst appearance on T2 sequence in 9 (69.23%) cases. Peri-lesion edema observed in 1 of case (7.69%), and spontaneous bleeding occured in 1 of case (7.69%). One case had ring-sign on Flair sequence. Nodular enhanced occurred in 2 (15.38%) cases after gadolinium administration.Preoperative plain CT (including PET-CT) studies dada were obtained in 8 cases. Hypodense appearance observed in 3 (37.5%) and isodense appearance observed in 5 (62.5%) cases. CT scans disclosed calcifications in 2 (25%) cases. A deformity of the overlying skull was apparent in 3 (37.5%) cases. Preoperative PET-CT studies dada were obtained from 8 cases. Reduced glucose metabolism occurred in all 8 cases, in which the area of reduced glucose metabolism was consistent with the lesion in 6 (75%) and beyond the lesion in 2 (25%) cases.The follow-up period was 15～50 months in surgical group, mean as 29 months. EagelⅠachieved in 7 (70%). EagelⅡin 2 (20%) and EagelⅢin 1 (10%) respectively. Complete seizure control achieved in all 4 cases of extended lesion resection group, and 3 of 4 (75%) cases of lesion resection group achieved seizure-free, seizure relapse in 1 of patient at the 3rd month after the operation. Hemiparesis occurred in one patient with DNET located in the premotor cortex and completely recovered with in 3 months. No persistent complications occurred.Three cases of the suspected dysembryoplastic neuroepithelial tumor had been followed up for 35,37 and 41 months respectively. The seizure showed less than twice per year in all 3 of cases. Repeated MR scan proved that the lesions were stable and no headache and other complain occurred in all cases.Conclusion1 Pseudocyst appearance on T2 sequence of MR image is the characteristic performance of DNET.2 Reduced glucose metabolism of the lesion on PET scan contributes to preoperative diagnosis of DNET.3 The only purpose of surgery for DNET is seizure control. The seizure-free could only achieved in those patients who had been totally removed the DNET itself and nearby epileptogenic foci.4 Epileptogenic foci resection in patients suffered from DNET with awaking craniotomy technique is superior to the one with conventional surgery for brain function protection.5 For the suspected cases with DNET, if the lesions involved eloquent area and seizure attack is not frequent, it's the better to wait and see with AEDs rather than reluctant lesion resection.Part 4 Gene microarray study on gene expression difference among focal cortical dysplasia (FCD)Ⅱb, dysembryoplastic neuroepithelial tumor (DNET) simple type and ganglioglioma (GG, WHO I)ObjectiveTo explore the gene expression difference among focal cortical dysplasia (FCD)Ⅱb, dysembryoplastic neuroepithelial tumor (DNET) simple type and ganglioglioma (GG, WHOⅠ).Materials and Methods Three of surgical specimens came from FCDⅡb, DNET simple type and GG respectively. After surgical removal, the samples were frozen and stored in a liquid nitrogen jar (-173℃) until use. The total RNA was isolated using TRIzol LS Reagent with Phase Lock Gel-Heavy tubes (Eppendorf), following the manufacturer's instructions. RNA integrity was determined using a nano-drop spectrophotometer. RNA Integrity and gDNA contamination Test were performed by Denaturing Agarose Gel Electrophoresis. The intensity of the 28S band was about twice than that of the 18S band, and OD260/OD280>2.0. RNA labeled with the GeneChip Expression 3=amplification one cycle target labeling system. Each RNA sample was hybridized to Agilent GeneChip System. After the hybridization, the GeneChips were washed and stained on a fluidics station (Agilent) and then scanned in a confocal scanner (Agilent GeneArray Scanner) according to the Agilent GeneChip Expression Analysis Manual. The GeneChip Human U133plusZ (Agilent Inc.) comprised more than 40,000 of well-characterized human genes. Comparisons were performed among three samples, requiring at least P<0.05 and twofold change for a significant difference (Student's t-test).ResultsAll the different expressed genes were under GO analysis, the results of which showed that there were 123 of genes overlap related biological process,88 of genes overlap related molecular function and 37 of genes overlap related cellular component in DNET vs GG. There were 112 of genes overlap related biological process,76 of genes overlap related molecular function and 33 of genes overlap related cellular component in DNET vs FCD. There were 81 of genes overlap related biological process,57 of genes overlap related molecular function and 40 of genes overlap related cellular component in GG vs FCD.According to the specific features, it was found that significantly lower level of expression of angiogenesis-related gene BTG1 and Wnt signaling pathway related genes FZD6 and FZD7 appeared in GG. No significant different expression of TSC1 and TSC2 genes were observed in GG, DNET and FCD samples. Overexpression of FGFR3 gene was observed in DNET. Significant overexpression of FGFR3 gene was observed in GG sample. Significant lower-expression of genes involved in sodium ionic channels, calcium ionic channels and GABA signaling were observed in DNET and GG samples.Conclusion1 Significant lower expressions of angiogenesis-related gene BTG1 and Wnt signaling pathway-related genes FZD6 and FZD7 were observed in GG samples, which might be related to the over-proliferation of glial cells causing tumorigenicity of GG.2 No significant different expressions of TSC1 and TSC2 genes were observed in GG, DNET and FCD sample.3 Overexpression of FGFR3 was observed in DNET, which might be the reason for gray matter thickening of DNET.4 Significant overexpression of FGFR3 was observed in GG sample, which might be related to the malignant transformation of GGs.5 Significant low-expressions of genes involved in sodium ionic channels, Calcium ionic channels and GABA signaling were observed in DNET and GG samples, which might be related to the epileptogenesis of those lesions.