Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia in Frontal Lobe Epilepsy: A New Clinico-Pathological Entity

[Structural heterogeneity of epileptic foci in local drug-resistant epilepsy]

BACKGROUND

To study etiopathogenesis is one of the most important tasks of modern neurology. Various types of structural changes occur in drug-resistant epilepsy (DRE); however, they are described as distinct phenomena.

OBJECTIVE

To provide a comprehensive characterization of structural changes in the cortex and adjacent white matter in the electrophysiological activity zone (in the epileptic focus) in patients undergoing surgery for DRE.

MATERIAL AND METHODS

Biopsy material of fragments of the temporal lobe and hippocampus from 16 patients aged 21 to 54 years (mean age, 25 years) with DRE were intraoperatively obtained at the Prof. A.L. Polenov Russian Research Institute of Neurosurgery. The investigators studied histological sections stained with H&E, toluidine blue according to the Nissl method and the Spielmeyer method, as well as the results of immunohistochemical reactions with glial fibrillary acidic protein (GFAP), vimentin, and neurofilaments (NF) (Dako antibodies, Denmark).

RESULTS

Histological examination revealed a set of heterogeneous changes, reflecting the complex pathogenetic interactions that developed during the formation of an epileptic focus. Structural brain damage involved both gray and white matter. Focal cortical dysplasia was diagnosed in 14 (87.5%) cases; white matter neuronal heterotopia in 100%; neuronal reactive and destructive changes in 100%; epileptic leukoencephalopathy (vascular demyelination, microcysts, sclerosis and dystonia, gliosis) in 100%, cortical atrophy in 12.5%, and hippocampal sclerosis in 20% (in 2 out of the 10 examinees).

CONCLUSION

The morphopathological heterogeneity in the structure of epileptic foci reflects the complexity of etiopathogenetic interactions, the polymorphism of epileptic manifestations, and the individual nature of formation of the epileptic system, which requires an integral approach to understanding the pathogenesis and morphogenesis of formation of the epileptic system and provides a direction for a personalized approach to epilepsy treatment.

Value of 7T MRI and post-processing in patients with nonlesional 3T MRI undergoing epilepsy presurgical evaluation

OBJECTIVE

Ultra-high-field 7-Tesla (7T) magnetic resonance imaging (MRI) offers increased signal-to-noise and contrast-to-noise ratios, which may improve visualization of cortical malformations. We aim to assess the clinical value of in vivo structural 7T MRI and its post-processing for the noninvasive identification of epileptic brain lesions in patients with pharmacoresistant epilepsy and nonlesional 3T MRI who are undergoing presurgical evaluation.

METHODS

Sixty-seven patients were included who had nonlesional 3T MRI by official radiology report. Epilepsy protocols were used for the 3T and 7T acquisitions. Post-processing of the 7T T1-weighted magnetization-prepared two rapid acquisition gradient echoes sequence was performed using the morphometric analysis program (MAP) with comparison to a normal database consisting of 50 healthy controls. Review of 7T was performed by an experienced board-certified neuroradiologist and at the multimodal patient management conference. The clinical significance of 7T findings was assessed based on intracranial electroencephalography (ICEEG) ictal onset, surgery, postoperative seizure outcomes, and histopathology.

RESULTS

Unaided visual review of 7T detected previously unappreciated subtle lesions in 22% (15/67). When aided by 7T MAP, the total yield increased to 43% (29/67). The location of the 7T-identified lesion was identical to or contained within the ICEEG ictal onset in 13 of 16 (81%). Complete resection of the 7T-identified lesion was associated with seizure freedom (P = .03). Histopathology of the 7T-identified lesions encountered mainly focal cortical dysplasia (FCD). 7T MAP yielded 25% more lesions (6/24) than 3T MAP, and showed improved conspicuity in 46% (11/24).

SIGNIFICANCE

Our data suggest a major benefit of 7T with post-processing for detecting subtle FCD lesions for patients with pharmacoresistant epilepsy and nonlesional 3T MRI.

Definitions and classification of malformations of cortical development: practical guidelines

Malformations of cortical development are a group of rare disorders commonly manifesting with developmental delay, cerebral palsy or seizures. The neurological outcome is extremely variable depending on the type, extent and severity of the malformation and the involved genetic pathways of brain development. Neuroimaging plays an essential role in the diagnosis of these malformations, but several issues regarding malformations of cortical development definitions and classification remain unclear. The purpose of this consensus statement is to provide standardized malformations of cortical development terminology and classification for neuroradiological pattern interpretation. A committee of international experts in paediatric neuroradiology prepared systematic literature reviews and formulated neuroimaging recommendations in collaboration with geneticists, paediatric neurologists and pathologists during consensus meetings in the context of the European Network Neuro-MIG initiative on Brain Malformations (https://www.neuro-mig.org/). Malformations of cortical development neuroimaging features and practical recommendations are provided to aid both expert and non-expert radiologists and neurologists who may encounter patients with malformations of cortical development in their practice, with the aim of improving malformations of cortical development diagnosis and imaging interpretation worldwide.

Epilepsy surgery for pediatric patients with mild malformation of cortical development

PURPOSE

The observation of mild malformation of cortical development (mMCD) has yet to have a major clinical impact due to the lack of clinical and research data. We characterized the clinical features, surgical outcomes, and postoperative seizure control patterns in pediatric patients with mMCD.

METHODS

We examined 40 patients with isolated mMCD who underwent resective surgery during a 10-year period.

RESULTS

The median age at seizure onset was 1.2 years, and the median age at surgery was 7.9 years. Twenty-seven patients (67.5%) presented with childhood-onset epileptic encephalopathy (21 Lennox-Gastaut syndrome, 6 West syndrome), and 13 patients (32.5%) presented with intractable focal epilepsy (10 extratemporal lesions, 3 temporal lesions). Twenty-one patients (52.5%) showed "suspected focal cortical malformation" on MRI, whereas 16 patients (40.0%) and 3 patients (7.5%) showed normal MRI findings or mild brain atrophy, respectively. The most common surgical procedures were two lobar resections (18 patients, 45.0%), followed by unilobar resections (12 patients, 30.0%) and resections exceeding two lobar boundaries (10 patients, 25.0%). As a final surgical outcome, 24 patients (60.0%) were ILAE Class 1-3. Discontinuation of all AEDs was possible for 36.8% of ILAE Class 1 patients. Regarding the seizure control pattern, fluctuating seizure control was observed most frequently (21 patients, 52.5%).

CONCLUSION

Our results suggest that mMCD is an important pathological finding in children related to a significant degree of epileptogenicity, and resective surgery can have positive outcomes. However, these patients showed unstable postoperative seizure control patterns with a high rate of late recurrence, suggesting difficulties in the surgical treatment of intractable epilepsy.

Genetic generalized epilepsies with frontal lesions mimicking migratory disorders on the epilepsy monitoring unit

Objective

Some patients with genetic generalized epilepsy (GGE) may present with ambiguous and atypical findings and even focal brain abnormalities. Correct diagnosis may therefore be difficult.

Methods

We retrospectively collected six patients investigated on the epilepsy monitoring unit with MRI abnormalities mimicking focal cortical dysplasia (FCD-like) or heterotopias, but with semiology and EEG features of GGE. We compared them to four additional patients with GGE and nonmigratory abnormalities.

Results

All six patients presented with frontal MRI lesions: radial ("transmantle," n = 4), cortical-subcortical (n = 1), and periventricular heterotopia (n = 1). Five had positive family histories. Semiologic lateralizing signs compatible with the lesion were seen in four. Five patients had 3/s spike-wave complexes, with an asymmetric appearance in three. Regional EEG changes matched with the side of the abnormality in three patients. Invasive EEG (n = 2) or postoperative outcomes (n = 3) argued against an ictogenic role of the MRI abnormalities. Histology showed mild malformation of cortical development, but no focal cortical dysplasia. The six patients were finally diagnosed with juvenile myoclonic epilepsy (n = 2), juvenile absence epilepsy (n = 2), or GGE not further specified (nfs, n = 2). Compared to these patients, the other four (final diagnoses: childhood absence epilepsy, n = 1; perioral myoclonia with absences, n = 1; and GGE nfs, n = 2) had no lateralizing EEG findings.

Significance

Patients with GGE may have coincidental MRI abnormalities. These cases are challenging as frontal epilepsy and GGE can present with similar semiologies. GGE with coincidental FCD-like lesions/heterotopias is in particular difficult to diagnose as patients have more lateralizing features (in semiology and EEG) than those with tumors. A detailed noninvasive presurgical evaluation may be justified. We point out red flags that may help to distinguish GGE from frontal epilepsy, even in the presence of brain abnormalities: 3/s spike waves (even if asymmetric), changing lateralizing signs at different times, and a positive family history hinting at GGE.

Isomorphic diffuse glioma is a morphologically and molecularly distinct tumour entity with recurrent gene fusions of MYBL1 or MYB and a benign disease course

The "isomorphic subtype of diffuse astrocytoma" was identified histologically in 2004 as a supratentorial, highly differentiated glioma with low cellularity, low proliferation and focal diffuse brain infiltration. Patients typically had seizures since childhood and all were operated on as adults. To define the position of these lesions among brain tumours, we histologically, molecularly and clinically analysed 26 histologically prototypical isomorphic diffuse gliomas. Immunohistochemically, they were GFAP-positive, MAP2-, OLIG2- and CD34-negative, nuclear ATRX-expression was retained and proliferation was low. All 24 cases sequenced were IDH-wildtype. In cluster analyses of DNA methylation data, isomorphic diffuse gliomas formed a group clearly distinct from other glial/glio-neuronal brain tumours and normal hemispheric tissue, most closely related to paediatric MYB/MYBL1-altered diffuse astrocytomas and angiocentric gliomas. Half of the isomorphic diffuse gliomas had copy number alterations of MYBL1 or MYB (13/25, 52%). Gene fusions of MYBL1 or MYB with various gene partners were identified in 11/22 (50%) and were associated with an increased RNA-expression of the respective MYB-family gene. Integrating copy number alterations and available RNA sequencing data, 20/26 (77%) of isomorphic diffuse gliomas demonstrated MYBL1 (54%) or MYB (23%) alterations. Clinically, 89% of patients were seizure-free after surgery and all had a good outcome. In summary, we here define a distinct benign tumour class belonging to the family of MYB/MYBL1-altered gliomas. Isomorphic diffuse glioma occurs both in children and adults, has a concise morphology, frequent MYBL1 and MYB alterations and a specific DNA methylation profile. As an exclusively histological diagnosis may be very challenging and as paediatric MYB/MYBL1-altered diffuse astrocytomas may have the same gene fusions, we consider DNA methylation profiling very helpful for their identification.

Temporal lobe "plus" epilepsy associated with oligodendroglial hyperplasia (MOGHE)

BACKGROUND

Mild malformation of cortical dysplasia (mMCD) with oligodendroglial hyperplasia (MOGHE) is an epilepsy-related pathologic entity highlighted in post-surgical specimens of frontal lobe epilepsy (FLE) patients.

AIMS OF THE STUDY

We present two temporal lobe epilepsy (TLE) cases with MOGHE and discuss clinical, neurophysiological, and neuroimaging features that may be indicative of surgical outcome.

METHODS

We identified two cases with MOGHE out of 30 temporal lobe epilepsy (TLE) surgical patient cohort, whose pathological distribution spared the hippocampal structures.

RESULTS

The TLE cases shared common features with the FLE series in terms of patient profiles, MRI findings and post-surgical outcome. TLE plus seizure semiology combined with extratemporal scalp electroencephalographic (EEG) and electrocorticographic (ECoG) epileptiform elements at a distance from the imaging lesion were suggestive of an underlying multifocal pathology.

CONCLUSIONS

MOGHE pathology has to be considered in the decision-making process for TLE epilepsy surgery when this constellation of features is met.

Epileptic Patient with Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia and Epilepsy (MOGHE): A Case Report and Review of the Literature

Introduction

There is an emerging interest in the literature about MOGHE (Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia and Epilepsy). We report the case of an epileptic patient with MOGHE.

Case Report

A 33-year-old male patient was suffering from refractory focal epilepsy since adolescence. MRI demonstrated increased T2/FLAIR signal intensity of right frontal lobe. Presurgical evaluation led to definition of epileptogenic network in a specific area of right frontal lobe. The resected specimen revealed MOGHE. Discussion. MOGHE appears to be a brain entity which shares some unique histopathological features. Review of the literature is in accordance with our patient's findings. The major neuropathological finding consists of areas with blurred gray-white matter boundaries due to heterotopic neurons in white matter and increased numbers of subcortical oligodendroglial cells with increased proliferation. MR abnormalities are present in T2/FLAIR sequences. It concerns patients with refractory frontal lobe epilepsy and appears to associate with unfavourable postsurgical outcome in seizure control.

Conclusion

More cases are needed in order to establish more data about this distinct entity in frontal lobe epilepsy. This could be valuable knowledge to patients and doctors concerning expectations or management of undesirable outcome in frontal lobe epilepsy surgery.

Age-related MR characteristics in mild malformation of cortical development with oligodendroglial hyperplasia and epilepsy (MOGHE)

BACKGROUND

Mild malformation of cortical development with oligodendroglial hyperplasia and epilepsy (MOGHE) is a newly described, rare histopathologic entity detected in resected brain tissue of patients with refractory epilepsies. It shows a predominantly frontal localization causing a difficult-to-treat epilepsy with onset usually in early childhood. Histologically, MOGHE is characterized by blurred gray-white-matter boundaries with increased numbers of heterotopic neurons in the subcortical white matter and increased density of oligodendroglia. Little is known, to date, about radiologic features of MOGHE. Here, we report typical and age-related magnetic resonance (MR) characteristics of MOGHE.

PATIENTS AND METHODS

Retrospective analysis of 40 preoperative MR images of 25 pediatric patients with MOGHE (m/f: 13/12) who underwent epilepsy surgery at a median age of 9.3 years at our center between 2003 and 2018. Median age at magnetic resonance imaging (MRI) was 5.2 years (1.5-20.7 years).

RESULTS

Two MR subtypes were found: subtype I with an increased laminar T2 and fluid attenuated inversion recovery (FLAIR) signal at the corticomedullary junction and subtype II with reduced corticomedullary differentiation because of increased signal of the adjacent white matter. Distribution of subtypes was age-related, with subtype I occurring between 1.5 and 5.1 years (median 2.6 years) and subtype II between 3.4 and 20.7 years (median 14.1 years). In one patient, MRI at the age of 2.7 years showed subtype I but had converted to subtype II by the age of 16 years. Histology revealed that in addition to the above mentioned typical findings of MOGHE, patchy areas of reduced density of myelin in 6 of 7 patients presenting subtype I out of 14 patients in which retrospective analysis regarding myelination was accessible.

CONCLUSION

Magnetic resonance characteristics in patients with MOGHE are age-related and seem to change from subtype I to subtype II probably because of maturational processes between 3 and 6 years. Patchy areas of hypomyelination in histology seem to disappear during brain maturation and may therefore represent the histologic correlate of laminar T2 and FLAIR hyperintensities in subtype I. This article is part of the Special Issue "Individualized Epilepsy Management: Medicines, Surgery and Beyond".

Review: Challenges in the histopathological classification of ganglioglioma and DNT: microscopic agreement studies and a preliminary genotype-phenotype analysis

Low-grade epilepsy-associated brain tumours (LEAT) are the second most common cause for drug-resistant, focal epilepsy, that is ganglioglioma (GG) and dysembryoplastic neuroepithelial tumours (DNT). However, molecular pathogenesis, risk factors for malignant progression and their frequent association with drug-resistant focal seizures remain poorly understood. This contrasts recent progress in understanding the molecular-genetic basis and targeted treatment options in diffuse gliomas. The Neuropathology Task Force of the International League Against Epilepsy examined available literature to identify common obstacles in diagnosis and research of LEAT. Analysis of 10 published tumour series from epilepsy surgery pointed to poor inter-rater agreement for the histopathology diagnosis. The Task Force tested this hypothesis using a web-based microscopy agreement study. In a series of 30 LEAT, 25 raters from 18 countries agreed in only 40% of cases. Highest discordance in microscopic diagnosis occurred between GG and DNT variants, when oligodendroglial-like cell patterns prevail, or ganglion cells were difficult to discriminate from pre-existing neurons. Suggesting new terminology or major histopathological criteria did not satisfactorily increase the yield of histopathology agreement in four consecutive trials. To this end, the Task Force applied the WHO 2016 strategy of integrating phenotype analysis with molecular-genetic data obtained from panel sequencing and 450k methylation arrays. This strategy was helpful to distinguish DNT from GG variants in all cases. The Task Force recommends, therefore, to further develop diagnostic panels for the integration of phenotype-genotype analysis in order to reliably classify the spectrum of LEAT, carefully characterize clinically meaningful entities and make better use of published literature.

MRI, Magnetoencephalography, and Surgical Outcome of Oligodendrocytosis versus Focal Cortical Dysplasia Type I

BACKGROUND AND PURPOSE

Abnormalities of oligodendrocytes have been reported in surgical specimens of patients with medically intractable epilepsy. The aim of this study was to compare the MR imaging, magnetoencephalography, and surgical outcome of children with oligodendrocytosis relative to focal cortical dysplasia I.

MATERIALS AND METHODS

Oligodendrocytosis included oligodendroglial hyperplasia, oligodendrogliosis, and oligodendroglial-like cells in the white matter, gray matter, or both from children with medically intractable epilepsy. Focal cortical dysplasia I included radial and tangential cortical dyslamination. The MR imaging, magnetoencephalography, type of operation, location, and seizure outcome of oligodendrocytosis, focal cortical dysplasia I, and oligodendrocytosis + focal cortical dysplasia I were compared.

RESULTS

Eighteen subjects (39.1%) had oligodendrocytosis, 21 (45.7%) had focal cortical dysplasia I, and 7 (15.2%) had oligodendrocytosis + focal cortical dysplasia I. There were no significant differences in the type of seizures, focal or nonfocal epileptiform discharges, magnetoencephalography, and MR imaging features, including high T1 signal in the cortex, high T2/FLAIR signal in the cortex or subcortical white matter, increased cortical thickness, blurring of the gray-white junction, or abnormal sulcation and gyration among those with oligodendrocytosis, focal cortical dysplasia I, or oligodendrocytosis + focal cortical dysplasia I (P > .01). There were no significant differences in the extent of resection (unilobar versus multilobar versus hemispherectomy), location of the operation (temporal versus extratemporal versus both), or seizure-free outcome of oligodendrocytosis, focal cortical dysplasia I, and oligodendrocytosis + focal cortical dysplasia I (P > .05).

CONCLUSIONS

Oligodendrocytosis shared MR imaging and magnetoencephalography features with focal cortical dysplasia I, and multilobar resection was frequently required to achieve seizure freedom. In 15% of cases, concurrent oligodendrocytosis and focal cortical dysplasia I were identified. The findings suggest that oligodendrocytosis may represent a mild spectrum of malformations of cortical development.

Histological and MRI markers of white matter damage in focal epilepsy

Growing evidence highlights the importance of white matter in the pathogenesis of focal epilepsy. Ex vivo and post-mortem studies show pathological changes in epileptic patients in white matter myelination, axonal integrity, and cellular composition. Diffusion-weighted MRI and its analytical extensions, particularly diffusion tensor imaging (DTI), have been the most widely used technique to image the white matter in vivo for the last two decades, and have shown microstructural alterations in multiple tracts both in the vicinity and at distance from the epileptogenic focus. These techniques have also shown promising ability to predict cognitive status and response to pharmacological or surgical treatments. More recently, the hypothesis that focal epilepsy may be more adequately described as a system-level disorder has motivated a shift towards the study of macroscale brain connectivity. This review will cover emerging findings contributing to our understanding of white matter alterations in focal epilepsy, studied by means of histological and ultrastructural analyses, diffusion MRI, and large-scale network analysis. Focus is put on temporal lobe epilepsy and focal cortical dysplasia. This topic was addressed in a special interest group on neuroimaging at the 70th annual meeting of the American Epilepsy Society, held in Houston December 2-6, 2016.

Histopathological Findings in Brain Tissue Obtained during Epilepsy Surgery

BACKGROUND

Detailed neuropathological information on the structural brain lesions underlying seizures is valuable for understanding drug-resistant focal epilepsy.

METHODS

We report the diagnoses made on the basis of resected brain specimens from 9523 patients who underwent epilepsy surgery for drug-resistant seizures in 36 centers from 12 European countries over 25 years. Histopathological diagnoses were determined through examination of the specimens in local hospitals (41%) or at the German Neuropathology Reference Center for Epilepsy Surgery (59%).

RESULTS

The onset of seizures occurred before 18 years of age in 75.9% of patients overall, and 72.5% of the patients underwent surgery as adults. The mean duration of epilepsy before surgical resection was 20.1 years among adults and 5.3 years among children. The temporal lobe was involved in 71.9% of operations. There were 36 histopathological diagnoses in seven major disease categories. The most common categories were hippocampal sclerosis, found in 36.4% of the patients (88.7% of cases were in adults), tumors (mainly ganglioglioma) in 23.6%, and malformations of cortical development in 19.8% (focal cortical dysplasia was the most common type, 52.7% of cases of which were in children). No histopathological diagnosis could be established for 7.7% of the patients.

CONCLUSIONS

In patients with drug-resistant focal epilepsy requiring surgery, hippocampal sclerosis was the most common histopathological diagnosis among adults, and focal cortical dysplasia was the most common diagnosis among children. Tumors were the second most common lesion in both groups. (Funded by the European Union and others.).

Multinodular and vacuolating neuronal tumors in epilepsy: dysplasia or neoplasia?

Multinodular and vacuolating neuronal tumor (MVNT) is a new pattern of neuronal tumour included in the recently revised WHO 2016 classification of tumors of the CNS. There are 15 reports in the literature to date. They are typically associated with late onset epilepsy and a neoplastic vs. malformative biology has been questioned. We present a series of ten cases and compare their pathological and genetic features to better characterized epilepsy‐associated malformations including focal cortical dysplasia type II (FCDII) and low‐grade epilepsy‐associated tumors (LEAT). Clinical and neuroradiology data were reviewed and a broad immunohistochemistry panel was applied to explore neuronal and glial differentiation, interneuronal populations, mTOR pathway activation and neurodegenerative changes. Next generation sequencing was performed for targeted multi‐gene analysis to identify mutations common to epilepsy lesions including FCDII and LEAT. All of the surgical cases in this series presented with seizures, and were located in the temporal lobe. There was a lack of any progressive changes on serial pre‐operative MRI and a mean age at surgery of 45 years. The vacuolated cells of the lesion expressed mature neuronal markers (neurofilament/SMI32, MAP2, synaptophysin). Prominent labelling of the lesional cells for developmentally regulated proteins (OTX1, TBR1, SOX2, MAP1b, CD34, GFAPδ) and oligodendroglial lineage markers (OLIG2, SMI94) was observed. No mutations were detected in the mTOR pathway genes, BRAF, FGFR1 or MYB. Clinical, pathological and genetic data could indicate that MVNT aligns more with a malformative lesion than a true neoplasm with origin from a progenitor neuro‐glial cell type showing aberrant maturation.

Marked accumulation of oligodendroglia-like cells in temporal lobe epilepsy with amygdala enlargement and hippocampal sclerosis

Although an increasing number of cases of temporal lobe epilepsy (TLE) with ipsilateral amygdala enlargement (AE) have been reported, there are few pathological reports, and no clear consensus has been established. Oligodendroglia or oligodendroglia-like cells (OLCs) have recently attracted attention in epilepsy studies. Here, we report the clinical and pathological findings of a 40-year-old male TLE patient with AE and hippocampal sclerosis, in whom histopathological study demonstrated remarkable clustering of OLCs around the uncus. The patient began to have refractory seizures at the age of 14, and preoperative MRI revealed left amygdala enlargement and left hippocampal atrophy. Other examinations were consistent with left mesial temporal epileptogenicity. He underwent surgical resection and achieved seizure freedom. Histopathological study of the amygdala showed swollen neurons with relatively large bodies and thick neurites, accompanied by vacuolar degeneration in the background. Additionally, there were marked clusters of OLCs with round nuclei and densely stained chromatin around the uncus. The OLCs were Olig2-positive. In the hippocampus, severe cell loss in CA1 and granule cell dispersion in the dentate gyrus were found. These findings may provide some insights for further pathological investigations of TLE with non-neoplastic AE.

Epileptogenic high-frequency oscillations skip the motor area in children with multilobar drug-resistant epilepsy

OBJECTIVE

Subtotal hemispherectomy involves the resection of multiple lobes in children with drug-resistant epilepsy, skipping the motor area (MA). We determined epileptogenicity using the occurrence rate (OR) of high-frequency oscillations (HFOs) and the modulation index (MI), demonstrating strength of coupling between HFO and slow wave. We hypothesized that epileptogenicity increased over the multiple lobes but skipped the MA.

METHODS

We analyzed 23 children (14 subtotal hemispherectomy; 9 multilobar resections). Scalp video-EEG and magnetoencephalography were performed before surgery. We analyzed the OR_(HFO) and MI_{(5 phases=0.5-8 Hz)} on electrodes of total area, resection areas, and MA. We compared the data between good [International League Against Epilepsy (ILAE) class I-II] and poor (III-VI) seizure outcome groups.

RESULTS

ILAE class Ia outcome was achieved in 18 children. Among the MI_{(5 phases)} in the resection areas, MI_{(3-4 Hz)} was the highest. The OR_(HFO) and MI_{(3-4 Hz)} in both total area and resection areas were significantly higher in the good seizure outcome group than in the poor outcome group. The OR_(HFO) and MI_{(3-4 Hz)} in resection areas were significantly higher than in the MA.

CONCLUSIONS

Our patients with multilobar drug-resistant epilepsy showed evidence of multifocal epileptogenicity that specifically skipped the MA.

SIGNIFICANCE

This is the first study demonstrating that the electrophysiological phenotype of multifocal epilepsy specifically skips the MA using OR_(HFO) and MI_{(3-4 Hz)}.

Network Reconstruction Reveals that Valproic Acid Activates Neurogenic Transcriptional Programs in Adult Brain Following Traumatic Injury

Objectives

To determine the mechanism of action of valproic acid (VPA) in the adult central nervous system (CNS) following traumatic brain injury (TBI) and hemorrhagic shock (HS).

Methods

Data were analyzed from different sources, including experiments in a porcine model, data from postmortem human brain, published studies, public and commercial databases.

Results

The transcriptional program in the CNS following TBI, HS, and VPA treatment includes activation of regulatory pathways that enhance neurogenesis and suppress gliogenesis. Genes which encode the transcription factors (TFs) that specify neuronal cell fate, including MEF2D, MYT1L, NEUROD1, PAX6 and TBR1, and their target genes, are induced by VPA. VPA represses genes responsible for oligodendrogenesis, maintenance of white matter, T-cell activation, angiogenesis, and endothelial cell proliferation, adhesion and chemotaxis. NEUROD1 has regulatory interactions with 38% of the genes regulated by VPA in a swine model of TBI and HS in adult brain. Hi-C spatial mapping of a VPA pharmacogenomic SNP in the GRIN2B gene shows it is part of a transcriptional hub that contacts 12 genes that mediate chromatin-mediated neurogenesis and neuroplasticity.

Conclusions

Following TBI and HS, this study shows that VPA administration acts in the adult brain through differential activation of TFs responsible for neurogenesis, genes responsible for neuroplasticity, and repression of TFs that specify oligodendrocyte cell fate, endothelial cell chemotaxis and angiogenesis.

Short title: Mechanism of action of valproic acid in traumatic brain injury

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-017-2130-6) contains supplementary material, which is available to authorized users.

Impaired oligodendroglial turnover is associated with myelin pathology in focal cortical dysplasia and tuberous sclerosis complex

Conventional antiepileptic drugs suppress the excessive firing of neurons during seizures. In drug-resistant patients, treatment failure indicates an alternative important epileptogenic trigger. Two epilepsy-associated pathologies show myelin deficiencies in seizure-related brain regions: Focal Cortical Dysplasia IIB (FCD) and cortical tubers in Tuberous Sclerosis Complex (TSC). Studies uncovering white matter-pathology mechanisms are therefore urgently needed to gain more insight into epileptogenesis, the propensity to maintain seizures, and their associated comorbidities such as cognitive defects. We analyzed epilepsy surgery specimens of FCD IIB (n = 22), TSC (n = 8), and other malformations of cortical development MCD (n = 12), and compared them to autopsy and biopsy cases (n = 15). The entire lesional pathology was assessed using digital immunohistochemistry, immunofluorescence and western blotting for oligodendroglial lineage, myelin and mTOR markers, and findings were correlated to clinical parameters. White matter pathology with depleted myelin and oligodendroglia were found in 50% of FCD IIB and 62% of TSC cases. Other MCDs had either a normal content or even showed reactive oligodendrolial hyperplasia. Furthermore, myelin deficiency was associated with increased mTOR expression and the lower amount of oligodendroglia was linked with their precursor cells (PDGFRa). The relative duration of epilepsy (normalized to age) also correlated positively to mTOR activation and negatively to myelination. Decreased content of oligodendroglia and missing precursor cells indicated insufficient oligodendroglial development, probably mediated by mTOR, which may ultimately lead to severe myelin loss. In terms of disease management, an early and targeted treatment could restore normal myelin development and, therefore, alter seizure threshold and improve cognitive outcome.

Novel Histopathological Patterns in Cortical Tubers of Epilepsy Surgery Patients with Tuberous Sclerosis Complex

Tuberous Sclerosis Complex (TSC) is a genetic hamartoma syndrome frequently associated with severe intractable epilepsy. In some TSC patients epilepsy surgery is a promising treatment option provided that the epileptogenic zone can be precisely delineated. TSC brain lesions (cortical tubers) contain dysmorphic neurons, brightly eosinophilic giant cells and white matter alterations in various proportions. However, a histological classification system has not been established for tubers. Therefore, the aim of this study was to define distinct histological patterns within tubers based on semi-automated histological quantification and to find clinically significant correlations. In total, we studied 28 cortical tubers and seven samples of perituberal cortex from 28 TSC patients who had undergone epilepsy surgery. We assessed mammalian target of rapamycin complex 1 (mTORC1) activation, the numbers of giant cells, dysmorphic neurons, neurons, and oligodendrocytes, and calcification, gliosis, angiogenesis, inflammation, and myelin content. Three distinct histological profiles emerged based on the proportion of calcifications, dysmorphic neurons and giant cells designated types A, B, and C. In the latter two types we were able to subsequently associate them with specific features on presurgical MRI. Therefore, these histopathological patterns provide consistent criteria for improved definition of the clinico-pathological features of cortical tubers identified by MRI and provide a basis for further exploration of the functional and molecular features of cortical tubers in TSC.