Interaction Between Akt1-Positive Neurons and Age at Surgery Is Associated With Surgical Outcome in Children With Isolated Focal Cortical Dysplasia:

Identifying cellular markers of focal cortical dysplasia type II with cell-type deconvolution and single-cell signatures

Focal cortical dysplasia (FCD) is a brain malformation that causes medically refractory epilepsy. FCD is classified into three categories based on structural and cellular abnormalities, with FCD type II being the most common and characterized by disrupted organization of the cortex and abnormal neuronal development. In this study, we employed cell-type deconvolution and single-cell signatures to analyze bulk RNA-seq from multiple transcriptomic studies, aiming to characterize the cellular composition of brain lesions in patients with FCD IIa and IIb subtypes. Our deconvolution analyses revealed specific cellular changes in FCD IIb, including neuronal loss and an increase in reactive astrocytes (astrogliosis) when compared to FCD IIa. Astrogliosis in FCD IIb was further supported by a gene signature analysis and histologically confirmed by glial fibrillary acidic protein (GFAP) immunostaining. Overall, our findings demonstrate that FCD II subtypes exhibit differential neuronal and glial compositions, with astrogliosis emerging as a hallmark of FCD IIb. These observations, validated in independent patient cohorts and confirmed using immunohistochemistry, offer novel insights into the involvement of glial cells in FCD type II pathophysiology and may contribute to the development of targeted therapies for this condition.

Predictors of seizure recurrence in patients with surgery for focal cortical dysplasia: pairwise and network meta-analysis and trial sequential analysis

OBJECT

The aim of this study was to determine the predictors of seizure recurrence in surgery for focal cortical dysplasia (FCD) by conducting a meta-analysis.

METHODS

Publications that met the pre-stated inclusion criteria were selected from PubMed and CNKI databases. Two authors extracted data independently about prognostic factors, surgical outcome, and clinical characteristics of participants. A fixed-effects model was used to calculate the summary of odds ratio (OR) with 95% confidence interval (CI).

RESULTS

Forty-eight studies were included in our meta-analysis. Three predictors of seizure recurrence (Engel class III/IV)-histological FCD type I, incomplete resection, and extratemporal location were determined; combined OR with 95% CI were 1.94 (95%CI 1.53-2.46), 12.06 (95%CI 7.32-19.88), and 1.91 (95%CI 1.06-3.44), respectively. Trial sequential analysis revealed that the outcomes had a sufficient sample size to reach firm conclusions. Furthermore, seizure location was not substantially modified by geographic region, while histological FCD type I and incomplete resection showed a significant association with seizure recurrence in different continents except Asia for incomplete resection. Sensitivity analyses restricted to studies for each variable yielded robust results. Little evidence of publication bias was observed. Meanwhile, the difference in the standard for outcome failed to influence the results for prognosis. Network meta-analysis including 13 trials comparing subtypes of FCD found the FCD IIb had the lowest seizure recurrence rate.

CONCLUSIONS

This meta-analysis suggests that histological FCD type I, incomplete resection, and extratemporal location are recurrence factors in patients with epilepsy surgery for FCD. In addition, FCD IIb is associated with the highest rates of postoperative seizure control among the subtypes of FCD, type I and type II.

MTOR pathway in focal cortical dysplasia type 2: What do we know?

Focal cortical dysplasia (FCD) is the most commonly encountered developmental malformation that causes refractory epilepsy. Focal cortical dysplasia type 2 is one of the most usual neuropathological findings in tissues resected therapeutically from patients with drug-resistant epilepsy. Unlike other types of FCD, it is characterized by laminar disorganization and dysplastic neurons, which compromise the organization of the six histologically known layers in the cortex; the morphology and/or cell location can also be altered. A comprehensive review about the pathogenesis of this disease is important because of the necessity to update the results reported over the past years. Here, we present an updated review through Pubmed about the mammalian target of rapamycin (MTOR) pathway in FCD type 2. A wide variety of aspects was covered in 44 articles related to molecular and cellular biology, including experiments in animal and human models. The first publications appeared in 2004, but there is still a lack of studies specifically for one type of FCD. With the advancement of techniques and greater access to molecular and cellular experiments, such as induced pluripotent stem cells (iPSCs) and organoids, it is believed that the trend is increasing the number of publications contributing to the achievement of new discoveries.

Clinical, imaging, and immunohistochemical characteristics of focal cortical dysplasia Type II extratemporal epilepsies in children: analyses of an institutional case series

OBJECTIVE Focal cortical dysplasia (FCD) Type II is divided into 2 subgroups based on the absence (IIA) or presence (IIB) of balloon cells. In particular, extratemporal FCD Type IIA and IIB is not completely understood in terms of clinical, imaging, biological, and neuropathological differences. The aim of the authors was to analyze distinctions between these 2 formal entities and address clinical, MRI, and immunohistochemical features of extratemporal epilepsies in children. METHODS Cases formerly classified as Palmini FCD Type II nontemporal epilepsies were identified through the prospectively maintained epilepsy database at the British Columbia Children's Hospital in Vancouver, Canada. Clinical data, including age of seizure onset, age at surgery, seizure type(s) and frequency, affected brain region(s), intraoperative electrocorticographic findings, and outcome defined by Engel's classification were obtained for each patient. Preoperative and postoperative MRI results were reevaluated. H & E-stained tissue sections were reevaluated by using the 2011 International League Against Epilepsy classification system and additional immunostaining for standard cellular markers (neuronal nuclei, neurofilament, glial fibrillary acidic protein, CD68). Two additional established markers of pathology in epilepsy resection, namely, CD34 and α-B crystallin, were applied. RESULTS Seven nontemporal FCD Type IIA and 7 Type B cases were included. Patients with FCD Type IIA presented with an earlier age of epilepsy onset and slightly better Engel outcome. Radiology distinguished FCD Types IIA and IIB, in that Type IIB presented more frequently with characteristic cortical alterations. Nonphosphorylated neurofilament protein staining confirmed dysplastic cells in dyslaminated areas. The white-gray matter junction was focally blurred in patients with FCD Type IIB. α-B crystallin highlighted glial cells in the white matter and subpial layer with either of the 2 FCD Type II subtypes and balloon cells in patients with FCD Type IIB. α-B crystallin positivity proved to be a valuable tool for confirming the histological diagnosis of FCD Type IIB in specimens with rare balloon cells or difficult section orientation. Distinct nonendothelial cellular CD34 staining was found exclusively in tissue from patients with MRI-positive FCD Type IIB. CONCLUSIONS Extratemporal FCD Types IIA and IIB in the pediatric age group exhibited imaging and immunohistochemical characteristics; cellular immunoreactivity to CD34 emerged as an especially potential surrogate marker for lesional FCD Type IIB, providing additional evidence that FCD Types IIA and IIB might differ in their etiology and biology. Although the sample number in this study was small, the results further support the theory that postoperative outcome-defined by Engel's classification-is multifactorial and determined by not only histology but also the extent of the initial lesion, its location in eloquent areas, intraoperative electrocorticographic findings, and achieved resection grade.

Prospective detection of cortical dysplasia on clinical MRI in pediatric intractable epilepsy

BACKGROUND

Cortical dysplasia is the most common cause of pediatric refractory epilepsy. MRI detection of epileptogenic lesion is associated with good postsurgical outcome. Additional electrophysiological information is suggested to be helpful in localization of cortical dysplasia. Educational measures were taken to increase the awareness of cortical dysplasia at our institution in the context of a recent International League Against Epilepsy (ILAE 2011) classification of cortical dysplasia.

OBJECTIVE

To determine changes in the rate of prospective identification of cortical dysplasia on an initial radiology report and also evaluate the benefit of MRI review as part of a multidisciplinary epilepsy conference in identifying previously overlooked MRI findings.

MATERIALS AND METHODS

We retrospectively evaluated surgically treated children with refractory epilepsy from 2007 to 2014 with cortical dysplasia on histopathology. We analyzed the initial radiology report, preoperative MRI interpretation at multidisciplinary epilepsy conference and subsequent retrospective MRI review with knowledge of the resection site. We recorded additional electrophysiological data and the presence of lobar concordance with the MRI findings.

RESULTS

Of 78 children (44 MRI lesional) evaluated, 18 had initially overlooked MRI findings. Comparing 2007-2010 to 2011-2014, there was improvement in the rate of overlooked findings on the initial radiology report (54% vs. 13% of lesional cases, respectively; P = 0.008). The majority (72%) were identified at a multidisciplinary conference with lobar concordance of findings with at least one additional electrophysiological investigation in 89%.

CONCLUSION

Awareness of current classification schemes of cortical dysplasia and image review in the context of a multidisciplinary conference can lead to improved MRI detection of cortical dysplasia in children.

Cytochrome c oxidase deficit is associated with the seizure onset zone in young patients with focal cortical dysplasia Type II

It has been postulated that mitochondrial dysfunction may be an important factor in epileptogenesis of intractable epilepsy. The current study tests the hypothesis that mitochondrial Complex IV (CIV) or cytochrome c oxidase dysfunction is associated with the seizure onset zone (SOZ) in patients with focal cortical dysplasia (FCD). Subjects were selected based on: age <19y; epilepsy surgery between May, 2010 and October, 2011; pathological diagnosis of isolated focal cortical dysplasia Type I (FCDI) or Type II (FCDII); and sufficient residual cortical tissue to conduct analysis of electron transport chain complex (ETC) activity in SOZ and adjacent cortical regions. In this retrospective study, patients were identified who had sufficient unfixed, frozen brain tissue for biochemical analysis in tissue homogenates. Specimens were subtyped using ILAE classification for FCD, and excluded if diagnosed with FCD Type III or dual pathology. Analysis of ETC activity in resected tissues was conducted independently and without knowledge of the identity, diagnosis, or clinical status of individual subjects. Seventeen patients met the inclusion criteria, including 6 FCDI and 11 FCDII. Comparison of adjacent cortical resections showed decreased CIV activity in the SOZ of the FCDII group (P = 0.003), but no significant CIV difference in adjacent tissues of the FCDI group. Because of the importance of CIV as the terminal and rate-limiting complex in the mitochondrial electron transport chain, these authors conclude that 1) a deficit of CIV is associated with the SOZ of patients with FCDII; 2) CIV deficiency may contribute to the spectrum of FCD neuropathology; and 3) further investigation of CIV in FCD may lead to the discovery of new targets for neuroprotective therapies for patients with intractable epilepsy.

Outcome after epilepsy surgery for cortical dysplasia in children

BACKGROUND AND PURPOSE

Epilepsy surgery for medically refractory epilepsy secondary to cortical dysplasia in children poses special challenges. We aim to review the current available literature on the outcome after epilepsy surgery for cortical dysplasia in children and critically evaluate the prognostic predictors of outcome.

METHODS

A comprehensive review of the literature was performed focusing on the outcome after epilepsy surgery for cortical dysplasia in children. Two large recent meta-analyses that included children and adults and several pediatric series of cortical dysplasia in children were reviewed.

RESULTS AND CONCLUSIONS

The overall seizure freedom rates range from 40 to 73 %, at about 2 years after surgery; most studies report 50-55% success rate. Complete resection of the epileptogenic lesion/zone remains the most important variable predictive of postoperative seizure freedom. Features unique to cortical dysplasia that limits our ability to ensure complete resection of the epileptogenic zone are reviewed.

Clinical, EEG, MRI, MEG, and surgical outcomes of pediatric epilepsy with astrocytic inclusions versus focal cortical dysplasia

OBJECTIVE

Astrocytic inclusions (AIs) have been identified on histologic specimens of patients with early onset seizures, and the proteomic contents have been described. The aim of this study was to compare the clinical, electroencephalography (EEG), magnetoencephalography (MEG), magnetic resonance imaging (MRI), and surgical outcomes of AIs relative to focal cortical dysplasia (FCD).

METHODS

We assessed the clinical manifestations, semiology, ictal and interictal features on video-EEG, MEG, MRI features, and surgical outcomes of children with histologically proven AIs compared to FCD.

RESULTS

Six children had AIs and 27 had FCD. Children with AIs had an earlier age at seizure onset, periodic spasms (all children), and interictal epileptiform discharges consisting of a mixture of generalized or diffuse hemispheric slow waves, sharp waves, spikes and polyspikes. Children with FCD were less likely to have spasms (4/27 [15%]), and the morphology of the diffuse hemispheric or generalized discharges were different from those of AI, consisting of spike-and-waves, polyspike-and-waves, sharp-and-slow waves, and paroxysmal fast activity. Patients with AIs were less likely to have tightly clustered MEG spike sources (3/6 [50%] vs. 23/27 [85%]), and more likely to demonstrate abnormal sulcation and gyration pattern (4/6 [67%] vs. 2/27 [7%]) and gray matter heterotopia (2/6 [33%] vs. 0/27 [0%]) than patients with FCD. Four children with AIs had resection and two had biopsy but did not undergo resection. Children with AIs had lower rates of seizure freedom after surgery compared to FCD (1/4 [25%] vs. 15/27 [56%], respectively).

SIGNIFICANCE

Although there were some similarities between AIs and FCD, patients with AIs were more likely to present with early onset periodic spasms, have unusual interictal epileptiform discharges, abnormal sulcation, gyration pattern, and gray matter heterotopia, and were less likely to be seizure free following surgical resection relative to FCD. Further study with a larger sample size is needed to validate our findings.

Cerebral glucose hypometabolism is associated with mitochondrial dysfunction in patients with intractable epilepsy and cortical dysplasia

OBJECTIVES

Metabolic imaging studies, such as positron emission tomography (PET), allow for an assessment of physiologic functioning of the brain, and [(18)F]fluoro-2-deoxyglucose (FDG)-PET is now a commonly used technique in presurgical epilepsy evaluations. Focal interictal decreases in glucose consumption are often but inconsistently concordant with the ictal onset area, and the underlying mechanisms are poorly understood. The current study tests the hypothesis that areas of glucose hypometabolism, determined by FDG-PET, are associated with mitochondrial dysfunction in patients with medically intractable epilepsy associated with isolated focal cortical dysplasia (FCD).

METHODS

Measures of electron transport chain (ETC) functioning and mitochondrial abnormalities (ETC complex biochemistry, protein kinase B subtype 1 (Akt1), glial fibrillary acidic protein (GFAP)) were assessed in surgical resection specimens that had hypometabolic abnormalities and those that were normal on FDG-PET. Determination of FDG-PET abnormalities was based on coregistration of statistical parametric mapping (SPM) results with postsurgical images.

RESULTS

Twenty-two patients (11 male, 11 female; mean age at the time of surgery 10.5 ± 4.4 years), with pathologically confirmed FCD, were included in this retrospective review. Complex IV function was found to be significantly reduced in areas of hypometabolism (p = 0.014), whereas there was a trend toward a significant reduction in complex II and III function in areas of hypometabolism (p = 0.08, p = 0.059, respectively). These decreases were independent of cortical dysplasia severity (p = 0.321) and other clinical epilepsy measures.

SIGNIFICANCE

This study suggests an association between glucose hypometabolism and reduced mitochondrial complex IV functioning, which is independent of the degree of cortical dysplasia. This supports the role of cellular energy failure as a potential mechanism for intractable epilepsy.

Magnetic resonance imaging abnormalities in the resection region correlate with histopathological type, gliosis extent, and postoperative outcome in pediatric cortical dysplasia

OBJECT.: The authors conducted a study to correlate histopathological features, MRI findings, and postsurgical outcomes in children with cortical dysplasia (CD) by performing a novel resection site-specific evaluation.

METHODS

The study cohort comprised 43 children with intractable epilepsy and CD. The MR image review was blinded to pathology but with knowledge of the resection location. An MRI score (range 0-7) was calculated for each resection region based on the number of imaging features of CD and was classified as "lesional" or "nonlesional" according to all imaging features. Outcome was determined using the International League Against Epilepsy (ILAE) scale. The determination of pathological CD type was based on the ILAE 2011 consensus classification system, and the cortical gliosis pattern was assessed on GFAP staining.

RESULTS

There were 89 resection regions (50 ILAE Type I, 29 Type IIa, and 10 Type IIb). Eleven (25.6%) of 43 children had more than one type of CD. The authors observed MRI abnormalities in 63% of patients, characteristic enough to direct resection (lesional) in 42%. Most MRI features, MRI score ≥ 3, and lesional abnormalities were more common in patients with Type II CD. Increased cortical signal was more common in those with Type IIb (70%) rather than Type IIa (17.2%) CD (p = 0.004). A good outcome was demonstrated in 39% of children with Type I CD and 72% of those with Type II CD (61% in Type IIa and 100% in Type IIb) (p = 0.03). A lesional MRI abnormality and an MRI score greater than 3 correlated with good outcome in 78% and 90% of patients, respectively (p < 0.03). Diffuse cortical gliosis was more prevalent in Type II CD and in resection regions exhibiting MRI abnormalities. Complete surgical exclusion of the MRI abnormality was associated with a better postoperative outcome.

CONCLUSIONS

This study provides a detailed correlation of MRI findings, neuropathological features, and outcomes in children with intractable epilepsy by using a novel resection site-specific evaluation. Because 25% of the patients had multiple CD subtypes, a regional analysis approach was mandated. Those children with lesional MRI abnormalities, Type II CD, and surgical exclusion of the MRI abnormality had better outcomes. Type II CD is more detectable by MRI than other types, partly because of the greater extent of associated gliosis in Type II. Although MRI findings were correlated with the pathological CD type and outcome in this study, the majority of patients (58%) did not have MRI findings that could direct surgical therapy, underscoring the need for improved MRI techniques for detection and for the continued use of multimodal evaluation methods in patient selection.