Types Of Malformations Of Cortical Development Research Articles

231 Postoperative Seizure Outcome of a Cohort of Patients With Drug Resistant Epilepsy and Malformations of Cortical Development Selected Predominantly by Non-invasive Evaluation

INTRODUCTION: Optimizing the surgical outcome of people with drug-resistant epilepsy (DRE) and malformations of cortical development (MCD) can be quite challenging. The studies are limited in this regard, especially from the low and middle income countries (LAMIC). METHODS: Between April, 2011 and March, 2023, 584 people with drug resistant epilepsy underwent surgery at NIMHANS, Bangalore, India. MCD as an underlying substrate have been identified among 170 patients. Different types of MCD, their pre-surgical evaluation, surgical strategy and outcome predictors have been studied. RESULTS: Cohort consists of 170 people with a mean age at surgery of 17.01 ± 10.94 (range 1.2 – 60) years. Mean age at seizure onset of 7.45 ± 7.39 (range 1 month to 40) years. The mean duration of epilepsy before surgery of 9.17 ± 7.58 (range 1-32) years. Males constituted 62.35% of patients (n= 106). Mean seizure score of the cohort was at 8.61 ± 1.34 (range 4-12 on a scale of 0 -12). Lifetime drugs tried by the cohort ranged from 1- 6 with mean of 2.85 ± 0.95. FCD was noted in 120 patients (70.587%). At a mean follow up of 4.66 ± 2.80 years, cohort had an Engel outcome class Ia, I, II, III and IV of 71.1%, 83.6%, 3.1%, 7.80% and 5.5 % respectively. Range of current AEDs used by the cohort is nil to 5, with mean of 2.28 ± 1.41. CONCLUSIONS: In this study, three variables were found to influence the outcome towards favourable arm of Engel class Ia. These factors are histopathology of FCD with balloon cells, glioneuronal aetiology and an age of less than 18 years at the time of surgery.

Malformations of cerebral development and clues from the peripheral nervous system: A systematic literature review.

Clinical manifestations of malformations of cortical development (MCD) are variable and can range from mild to severe intellectual disability, cerebral palsy and drug-resistant epilepsy. Besides common clinical features, non-specific or more subtle clinical symptoms may be present in association with different types of MCD. Especially in severely affected individuals, subtle but specific underlying clinical symptoms can be overlooked or overshadowed by the global clinical presentation. To facilitate the interpretation of genetic variants detailed clinical information is indispensable. Detailed (neurological) examination can be helpful in assisting with the diagnostic trajectory, both when referring for genetic work-up as well as when interpreting data from molecular genetic testing. This systematic literature review focusses on different clues derived from the neurological examination and potential further work-up triggered by these signs and symptoms in genetically defined MCDs. A concise overview of specific neurological findings and their associations with MCD subtype and genotype are presented, easily applicable in daily clinical practice. The following pathologies will be discussed: neuropathy, myopathy, muscular dystrophies and spastic paraplegia. In the discussion section, tips and pitfalls are illustrated to improve clinical outcome in the future.

Personalized microstructural evaluation using a Mahalanobis-distance based outlier detection strategy on epilepsy patients' DTI data - Theory, simulations and example cases.

Quantitative MRI methods have recently gained extensive interest and are seeing substantial developments; however, their application in single patient vs control group comparisons is often limited by inherent statistical difficulties. One such application is detecting malformations of cortical development (MCDs) behind drug resistant epilepsies, a task that, especially when based solely on conventional MR images, may represent a serious challenge. We aimed to develop a novel straightforward voxel-wise evaluation method based on the Mahalanobis-distance, combining quantitative MRI data into a multidimensional parameter space and detecting lesion voxels as outliers. Simulations with standard multivariate Gaussian distribution and resampled DTI-eigenvalue data of 45 healthy control subjects determined the optimal critical value, cluster size threshold, and the expectable lesion detection performance through ROC-analyses. To reduce the effect of false positives emanating from registration artefacts and gyrification differences, an automatic classification method was applied, fine-tuned using a leave-one-out strategy based on diffusion and T1-weighted data of the controls. DWI processing, including thorough corrections and robust tensor fitting was performed with ExploreDTI, spatial coregistration was achieved with the DARTEL tools of SPM12. Additional to simulations, clusters of outlying diffusion profile, concordant with neuroradiological evaluation and independent calculations with the MAP07 toolbox were identified in 12 cases of a 13 patient example population with various types of MCDs. The multidimensional approach proved sufficiently sensitive in pinpointing regions of abnormal tissue microstructure using DTI data both in simulations and in the heterogeneous example population. Inherent limitations posed by registration artefacts, age-related differences, and the different or mixed pathologies limit the generalization of specificity estimation. Nevertheless, the proposed statistical method may aid the everyday examination of individual subjects, ever so more upon extending the framework with quantitative information from other modalities, e.g. susceptibility mapping, relaxometry, or perfusion.

Beyond the Exome: The Non-coding Genome and Enhancers in Neurodevelopmental Disorders and Malformations of Cortical Development.

The development of the human cerebral cortex is a complex and dynamic process, in which neural stem cell proliferation, neuronal migration, and post-migratory neuronal organization need to occur in a well-organized fashion. Alterations at any of these crucial stages can result in malformations of cortical development (MCDs), a group of genetically heterogeneous neurodevelopmental disorders that present with developmental delay, intellectual disability and epilepsy. Recent progress in genetic technologies, such as next generation sequencing, most often focusing on all protein-coding exons (e.g., whole exome sequencing), allowed the discovery of more than a 100 genes associated with various types of MCDs. Although this has considerably increased the diagnostic yield, most MCD cases remain unexplained. As Whole Exome Sequencing investigates only a minor part of the human genome (1–2%), it is likely that patients, in which no disease-causing mutation has been identified, could harbor mutations in genomic regions beyond the exome. Even though functional annotation of non-coding regions is still lagging behind that of protein-coding genes, tremendous progress has been made in the field of gene regulation. One group of non-coding regulatory regions are enhancers, which can be distantly located upstream or downstream of genes and which can mediate temporal and tissue-specific transcriptional control via long-distance interactions with promoter regions. Although some examples exist in literature that link alterations of enhancers to genetic disorders, a widespread appreciation of the putative roles of these sequences in MCDs is still lacking. Here, we summarize the current state of knowledge on cis-regulatory regions and discuss novel technologies such as massively-parallel reporter assay systems, CRISPR-Cas9-based screens and computational approaches that help to further elucidate the emerging role of the non-coding genome in disease. Moreover, we discuss existing literature on mutations or copy number alterations of regulatory regions involved in brain development. We foresee that the future implementation of the knowledge obtained through ongoing gene regulation studies will benefit patients and will provide an explanation to part of the missing heritability of MCDs and other genetic disorders.

Hypervascularization in mTOR-dependent focal and global cortical malformations displays differential rapamycin sensitivity.

Patients with mammalian target of rapamycin (mTOR)-dependent malformations of cortical development (MCDs) associated with seizures display hyperperfusion and increased vessel density of the dysmorphic cortical tissue. Some studies have suggested that the vascular defect occurred independently of seizures. Here, we further examined whether hypervascularization occurs in animal models of global and focal MCD with and without seizures, and whether it is sensitive to the mTOR blocker, rapamycin, that is approved for epilepsy treatment in tuberous sclerosis complex. We used two experimental models of mTOR-dependent MCD consisting of conditional transgenic mice containing Tsc1null cells in the forebrain generating a global malformation associated with seizures and of wild-type mice containing a focal malformation in the somatosensory cortex generated by in utero electroporation (IUE) that does not lead to seizures. Alterations in blood vessels and the effects of a 2-week-long rapamycin treatment on these phenotypes were assessed in juvenile mice. Blood vessels in both the focal and global MCDs of postnatal day 14 mice displayed significant increase in vessel density, branching index, total vessel length, and decreased tissue lacunarity. In addition, rapamycin treatment (0.5mg/kg, every 2days) partially rescued vessel abnormalities in the focal MCD model, but it did not ameliorate the vessel abnormalities in the global MCD model that required higher rapamycin dosage for a partial rescue. Here, we identified hypervascularization in mTOR-dependent MCD in the absence of seizures in young mice, suggesting that increased angiogenesis occurs during development in parallel to alterations in corticogenesis. In addition, a predictive functional outcome is that dysplastic neurons forming MCD will have better access to oxygen and metabolic supplies via their closer proximity to blood vessels. Finally, the difference in rapamycin sensitivity between a focal and global MCD suggest that rapamycin treatment will need to be titrated to match the type of MCD.

Epilepsy patients with malformations of cortical development: Experience from a tertiary care centre in Eastern India

Malformations of cortical development (MCD) are lesions produced by insult to the developing neocortex. MCD are frequently associated with refractory epilepsy. Clinical and electrophysiologic findings of MCD are variable. Our aims in this study are to identify cases of MCD in patients having epilepsy, to study the semiology of seizure, to look for associated risk factors and to correlate the semiology of seizure with the electroencephalographic (EEG) and magnetic resonance imaging (MRI) findings. We studied 54 patients with MCD (from January 2011 till October 2012). Detailed medical and family histories were obtained in addition to neurological examinations and routine EEG evaluations. There were 29 (53.7%) males and 25 (46.3%) females, with ages ranging from 5 mo to 43 yr. The focal cortical dysplasias cases were sixteen (29.6%), schizencephaly eight (14.8%), polymicrogyria eight (14.8%), dysembryoblastic neuroepithelial tumor six (11.1%), lissencephaly five (9.3%), ganglioglioma three (5.6%), heterotopias three (5.6%), hemimegalencephaly two (3.7%), cortical hamartomas of tuberous sclerosis two (3.7%) and mixed lesion in one (1.8%). Overall, 40 (74.1%) cases had partial seizures. The EEG revealed interictal epileptiform discharges in 27 (50.0%) with the rest being normal. The commonest type of MCD was the focal cortical dysplasia. Most (74.1%) cases had focal seizures. There was poor correlation between semiology of seizure with the EEG and MRI findings. There was no history of any antenatal maternal infection or drug exposure. No risk factor except for positive family history was identified.

Epileptogenic malformations of cortical development: when evolution goes awry

Background. Since the time of its origin in a mammalian ancestor, perhaps 250 million years ago, the neocortex has undergone expansion in both relative and absolute size. The complexity of the brain in vertebrates is proportional to the elaboration of the mechanisms controlling cortical development. Malformations of cortical development (MCD) are classified into three major groups that recapitulate the main developmental steps: cell proliferation, neuronal migration, or postmigrational cortical organization and connectivity. The main clinical manifestations of MCDs are epilepsy and / or intellectual disability. Seizures are the most common clinical feature, at least 75% of patients with MCDs will have epilepsy. Recent advances in neuroimaging techniques and revolutionary achievements in molecular biology led to an explosive increase in our knowledge of cerebral cortex development and malformations of cortical development (MCD). So far, more than 100 genes were associated with one or more types of MCD. However, the genetic cause still remains unidentified in the majority of cases. Conclusions. Investigations of human malformations of cortical development as of a model of impaired neurodevelopment gave a lot of important insights into normal and abnormal brain development processes and practical benefits to MCD patients and their families. Recent achievements in genetic technologies led to a real explosion in such knowledge and are expected to yield even more additional information in the near future.

Epilepsy surgery in children and adolescents with malformations of cortical development—Outcome and impact of the new ILAE classification on focal cortical dysplasia

To determine long-term efficacy and safety of epilepsy surgery in children and adolescents with malformations of cortical development (MCD) and to identify differences in seizure outcome of the various MCD subgroups. Special focus was set on the newly introduced International League Against Epilepsy (ILAE) classification of focal cortical dysplasia (FCD). This is a single center retrospective cross-sectional analysis of prospectively collected data. age at surgery <18 years, pre-surgical evaluation and epilepsy surgery performed at the Vienna pediatric epilepsy center, histologically proven MCD, complete follow-up data for at least 12 months. Clinical variables evaluated: type and localization of MCD, type of surgery and a variety of clinical characteristics reported to be associated with (un-)favorable outcomes. MCD were classified following the existing classification schemes (Barkovich et al., 2012. Brain. 135, 1348-1369; Palmini et al., 2004. Neurology. 62, S2-S8) and the ILAE classification for FCD recently proposed by Blümcke in 2011. Seizure outcome was classified using the ILAE classification proposed by Wieser in 2001. 60 Patients (51.7% male) were included. Follow up was up to 14 (mean 4.4 ± 3.2) years. Mean age at surgery was 8.0 ± 6.0 (median 6.0) years; mean age at epilepsy onset was 2.9 ± 3.2 (median 2.0) years; duration of epilepsy before surgery was 4.8 ± 4.4 (median 3.0) years. 80% of the patients were seizure free at last follow-up. AEDs were successfully withdrawn in 56.7% of all patients. Extended surgery, lesion localization in the temporal lobes and absence of inter-ictal spikes in postsurgical EEG recordings were predictive of favorable seizure outcomes after surgery. However, no association was found between outcome and MCD sub-types. Epilepsy surgery is highly effective in carefully selected drug-resistant children with MCD. Surrogate markers for complete resection of the epileptogenic zone remain the only significant predictors for seizure freedom after surgery.

Different structures involved during ictal and interictal epileptic activity in malformations of cortical development: an EEG-fMRI study

Malformations of cortical development (MCDs) are commonly complicated by intractable focal epilepsy. Epileptogenesis in these disorders is not well understood and may depend on the type of MCD. The cellular mechanisms involved in interictal and ictal events are notably different, and could be influenced independently by the type of pathology. We evaluated the relationship between interictal and ictal zones in eight patients with different types of MCD in order to better understand the generation of these activities: four had nodular heterotopia, two focal cortical dysplasia and two subcortical band heterotopia (double-cortex). We used the non-invasive EEG-fMRI technique to record simultaneously all cerebral structures with a high spatio-temporal resolution. We recorded interictal and ictal events during the same session. Ictal events were either electrical only or clinical with minimal motion. BOLD changes were found in the focal cortical dysplasia during interictal and ictal epileptiform events in the two patients with this disorder. Heterotopic and normal cortices were involved in BOLD changes during interictal and ictal events in the two patients with double cortex, but the maximum BOLD response was in the heterotopic band in both patients. Only two of the four patients with nodular heterotopia showed involvement of a nodule during interictal activity. During seizures, although BOLD changes affected the lesion in two patients, the maximum was always in the overlying cortex and never in the heterotopia. For two patients intracranial recordings were available and confirm our findings. The dysplastic cortex and the heterotopic cortex of band heterotopia were involved in interictal and seizure processes. Even if the nodular gray matter heterotopia may have the cellular substrate to produce interictal events, the often abnormal overlying cortex is more likely to be involved during the seizures. The non-invasive BOLD study of interictal and ictal events in MCD patients may help to understand the role of the lesion in epileptogenesis and also determine the potential surgical target.

The clinical spectrum of malformations of cortical development

Malformations of cortical development (MCD) usually manifest in childhood with epilepsy, developmental delay and focal neurological abnormalities. To evaluate the presentation and severity of epilepsy in the different types of MCD. We evaluated the first 100 consecutive patients with a neuroimaging diagnosis of MCD. They were identified among all the high resolution magnetic resonance imaging exams performed at our service between 1997 and 2001. The causes of referral were diverse, according to the routine of the neurology outpatient clinic. After magnetic resonance imaging diagnosis of the subtype of MCD a detailed clinical assessment was performed. There were 55 females and 45 males, with ages ranging from five months to 71 years old (mean=15.2 years). Seventy-seven patients presented with epilepsy. Sixty-one had partial epileptic syndromes, 13 secondary generalized syndromes, and in three, the type of epileptic syndrome could not be established. Epilepsy was less frequent in patients with the MCD subtypes of polymicrogyria and schizencephaly (p<0.001). Patients with schizencephaly and polymicrogyria had their seizures more easily controlled by antiepileptic drugs (p<0.001). That the frequency of epilepsy is lower and seizures are more easily controlled in the setting of polymicrogyria and schizencephaly. Patients with MCD frequently present with secondary generalized epilepsy early in childhood.

Malformations of Cerebral Cortical Development

Malformations of cortical development (MCDs) comprise a variable spectrum of clinical, neuroradiologic, and histopathologic findings. MCDs are increasingly recognized as significant causes of epilepsy, developmental delays, and congenital neurologic deficits. The aim of this study was to determine the types, relative frequencies, and clinical and imaging features of MCDs. Data were collected in 2 hospitals and a medical imaging center during a 9-year period. Twenty-six patients (17 men and 9 women; age range, 5 mo to 29 y; mean age, 10.8 y) with an MCD were evaluated. The results of magnetic resonance imaging studies were retrospectively reviewed for type, extension, and classification of the malformations and for associated findings. Clinical findings were obtained by a review of the patients' medical records. Of the patients studied, epilepsy was present in 65%, mental and/or motor retardation was identified in 34.6%, and skin lesions were noted in 15%. The following types of MCD were identified: malformations of the heterotopic gray matter in 35% of the subjects, focal cortical dysplasia (23%), subependymal and cortical tubers (19%), pachygyria (15%), polymicrogyria (15%), schizencephaly (15%), and type 1 lissencephaly (8%). Approximately, 27% of the subjects had the following other types of cerebral malformation: callosal agenesis (8%), ventriculomegaly (8%), or agenesis of the septum pellucidum (4%). Our study indicated that the most common forms of MCD are heterotopia and focal cortical dysplasia. Patients with an MCD tended to have a higher prevalence of epilepsy, developmental delays, and neurologic deficits. Most patients with heterotopia had other malformations of cortical dysplasia. Some patients with an MCD also exhibited other malformations of the brain.

Electroclinical and magnetoencephalographic studies in epilepsy patients with polymicrogyria

Rationale: Malformations of cortical development (MCDs) are increasingly recognized as important causes of developmental delay, epilepsy, and other neurological disorders. Polymicrogyria, a type of MCD, is characterized by many small microgyria separated by shallow sulci, a slightly thick cortex, neuronal heterotopia and often enlarged ventricles. The present descriptive study analysis the electroclinical and magnetoencephalographic findings of patients with epilepsy and polymicrogyria without schizencephaly. Methods: We studied six patients; mean age was 27 years, who had evidence of polymicrogyria in neuroimaging studies. A single equivalent-current dipole (ECD) model was used to estimate the location of epileptiform spike dipole sources. Analysis was performed on selected data segments containing MEG spikes. MEG results were combined with MRI to create magnetic source images (MSI). Results: In all cases we present results of MRI, MEG, Video-EEG monitoring, and other functional neuroimaging studies if performed. Conclusions: MSI can be used to accurately localize sources of epileptiform discharges. As such MSI can play a role of directly determining the functional epileptogenic significance of abnormalities depicted in imaging.

Interrelationship of genetics and prenatal injury in the genesis of malformations of cortical development.

Although the causes of some malformations of cortical development (MCD) have been established, others remain unclear. There are several lines of evidence supporting the theory of a complex mechanism that involves genetic and environmental factors. To investigate the interrelationship of genetics and prenatal injury in the genesis of MCD. A series of 76 consecutive patients with MCD and their families were systematically questioned about their family histories of epilepsy or other neurological impairment and the occurrence of prenatal events. Whenever possible, magnetic resonance imaging was performed in other family members if MCD was suspected or in the presence of any neurological impairment. Patients were divided into 3 groups according to the type of MCD. Patients in group 1 had focal cortical dysplasia, group 2 had heterotopias (periventricular or subcortical) or agyria-pachygyria, and group 3 had polymicrogyria or schizencephaly. These findings were also compared with a disease-control group of 40 consecutive patients with epilepsy but without MCD. Neurology clinic of a university hospital. Of the 76 patients with MCD, 21 (28%) had focal cortical dysplasia, 19 (25%) had heterotopias or agyria-pachygyria, and 36 (47%) had polymicrogyria or schizencephaly. There were 39 men and 37 women, aged 2 to 52 years (mean age, 13 years). In group 2, 6 patients (32%) had a family history of MCD, mental retardation, or miscarriages, suggesting a genetic predisposition. In group 3, family history of MCD was present in 5 patients (14%). Prenatal events occurred in 28 patients with MCD (37%) and 2 controls (5%) and were more frequent in patients with heterotopia or agyria-pachygyria and polymicrogyria (P<.001). Conversely, epilepsy occurred in all patients in group 1, in 17 patients (89%) in group 2, and in 17 patients (47%) in group 3. In group 3, epilepsy was less frequent (P<.001) and also more easily controlled (P =.005) than in other forms of MCD. Our findings support the idea of a spectrum among the different types of MCD. Focal cortical dysplasia (group 1) is associated with more frequent and severe epilepsy and less important genetic and prenatal events, heterotopias and agyria-pachygyria (group 2) are frequently associated with genetic predisposition, and polymicrogyria and schizencephaly (group 3) are less frequently associated with epilepsy but have a stronger association with genetic and detectable prenatal events.

Seizure outcome after functional hemispherectomy for malformations of cortical development.

MRI features were correlated with postsurgical seizure outcome in patients with hemispheric malformations of cortical development (MCD). After functional hemispherectomy, 5 of 6 patients (83%) with hemimegalencephaly had persistent, although markedly improved, seizures; 5 of 6 patients (83%) with relative preservation of part of one lobe or atrophy were seizure free. Hemimegalencephaly and other types of hemispheric MCD appear to differ in prognosis for freedom from seizures after functional hemispherectomy.

Surgery for malformations of cortical development causing epilepsy.

Malformations of cortical development (MCD) are responsible for many cases of refractory epilepsy in adults and children. The results of surgical treatment are difficult to assess from the published literature. Judging from the limited number of adequately reported cases, approximately 40% of all cases of MCD treated surgically may be rendered seizure-free over a minimum 2-year follow-up period. This figure is the same for focal cortical dysplasia (FCD), the most common variety of MCD in surgical reports. In comparison with outcome for epilepsy associated with hippocampal sclerosis, this figure is low. Part of the difference may be artificial and related to limited reporting. Much of the difference is likely to relate to the complex underlying biology of MCD. Analysis of epileptogenesis in MCD has been undertaken. Different types of MCD have different sequelae. Some varieties are intrinsically epileptogenic; these include FCD and heterotopia. Although in most cases, the visualized MCD lies within the region of brain responsible for generating seizures (the epileptogenic zone), it may not constitute the entire epileptogenic zone in all cases. For polymicrogyria and schizencephaly in particular, the visualized abnormalities are probably not the most important component of the epileptogenic zone. There is evidence that the epileptogenic zone is spatially distributed and also, in some cases, temporally distributed. These findings may explain poor surgical outcome and the inadequacy of current presurgical evaluative methods. New preoperative techniques offer the opportunity of improved presurgical planning and selection of cases more likely to be rendered seizure-free by current surgical techniques. Of paramount importance is improved reporting. The establishment of a central registry may facilitate this aim. Specific recommendations are made for surgical strategies based on current experience and understanding.

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Malformations of cortical development (MCD) represent a major cause of developmental disabilities and severe epilepsy. Advances in imaging and genetics have improved the diagnosis and classification of these conditions. Up to now, eight genes have been involved in different types of MCD. Lissencephaly-pachygyria and subcortical band heterotopia (SBH) represent a malformative spectrum resulting from mutations of either LIS1 or DCX genes. LIS1 mutations cause a more severe malformation in the posterior brain regions. DCX mutations usually cause anteriorly predominant lissencephaly in males and SBH in female patients. Additional forms are X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia associated with mutations of the ARX gene. Lissencephaly with cerebellar hypoplasia (LCH) encompass heterogeneous disorders named LCH types a to d. LCHa is related to mutation in LIS1 or DCX, LCHb with mutation of the RELN gene, and LCHd could be related to the TUBA1A gene.Polymicrogyria encompasses a wide range of clinical, etiological, and histological findings. Among several syndromes, recessive bilateral fronto-parietal polymicrogyria has been associated with mutations of the GPR56 gene. Bilateral perisylvian polymicrogyria has been associated with mutations in the SRPX2 gene in a few individuals and with linkage to chromosome Xq28 in a some other families.X-linked bilateral periventricular nodular heterotopia (PNH) consists of PNH with focal epilepsy in females and prenatal lethality in males. Filamin A (FLNA) mutations have been reported in some families and in sporadic patients. It is possible to infer the most likely causative gene by brain imaging studies and other clinical findings.