mTOR-therapy and targeted treatment opportunities in mTOR-related epilepsies associated with cortical malformations.

Dysregulation of the mTOR pathway is now well documented in several neurodevelopmental disorders associated with epilepsy. Mutations of mTOR pathway genes are involved in tuberous sclerosis complex (TSC) as well as in a range of cortical malformations from hemimegalencephaly (HME) to type II focal cortical dysplasia (FCD II), leading to the concept of "mTORopathies" (mTOR pathway-related malformations). This suggests that mTOR inhibitors (notably rapamycin (sirolimus), and everolimus) could be used as antiseizure medication. In this review, we provide an overview of pharmacological treatments targeting the mTOR pathway for epilepsy based on lectures from the ILAE French Chapter meeting in October 2022 in Grenoble. There is strong preclinical evidence for the antiseizure effects of mTOR inhibitors in TSC and cortical malformation mouse models. There are also open studies on the antiseizure effects of mTOR inhibitors, as well as one phase III study showing the antiseizure effect of everolimus in TSC patients. Finally, we discuss to which extent mTOR inhibitors might have properties beyond the antiseizure effect on associated neuropsychiatric comorbidities. We also discuss a new way of treatment on the mTOR pathways.

A Case of a Solitary Cortical Tuber with No Other Manifestations of Tuberous Sclerosis Complex Mimicking Focal Cortical Dysplasia Type II with Calcification.

Cortical tubers are one of the typical intracranial manifestations of tuberous sclerosis complex (TSC). Multiple cortical tubers are easy to diagnose as TSC; however, a solitary cortical tuber without any other cutaneous or visceral organ manifestations can be confused with other conditions, particularly focal cortical dysplasia. We report a surgical case of refractory epilepsy caused by a solitary cortical tuber mimicking focal cortical dysplasia type II, and describe the radiological, electrophysiological, and histopathological findings of our case.

Isolated cortical tuber in an infant with genetically confirmed tuberous sclerosis complex 1 presenting with symptomatic West syndrome.

Tuberous sclerosis complex (TSC) is an autosomal dominant hereditary disorder caused by mutations in either TSC1 on chromosome 16 or TSC2 on chromosome 9, clinically characterized mainly by facial angiofibroma, epilepsy, and intellectual disability. Cortical dysplasias, subependymal nodules, and subependymal giant cell astrocytoma are characteristic central nervous system lesions among 11 major features in the current clinical diagnostic criteria for TSC. We encountered an unusual case of genetically confirmed TSC1 presenting with symptomatic West syndrome due to an isolated cortical dysplasia in the left occipital lobe of a six-month-old male infant who did not meet the clinical diagnostic criteria for TSC. The patient underwent left occipital lesionectomy at age 11 months and has been seizure-free for nearly six years since then. Histological examination of the resection specimen revealed cortical neuronal dyslamination with abundant dysmorphic neurons and ballooned cells, consistent with focal cortical dysplasia (FCD) type IIb. However, the lesion was also accompanied by unusual features, including marked calcifications, dense fibrillary gliosis containing abundant Rosenthal fibers, CD34-positive glial cells with abundant long processes confined to the dysplastic cortex, and multiple nodular lesions occupying the underlying white matter, consisting exclusively of ballooned cell and/or balloon-like astrocytes with focal calcifications. Genetic testing for TSC1 and TSC2 using the patient's peripheral blood revealed a germline heterozygous mutation in exon 7 (NM_000368.5: c.526dupT, p.Tyr176fs) in TSC1. Isolated FCD with unusual features such as calcification, dense fibrillary gliosis, Rosenthal fibers and/or subependymal nodule-like lesions in the white matter may indicate the possibility of a cortical tuber even without a clinical diagnosis of TSC. Identification of such histopathological findings has significant implications for early and accurate diagnosis and treatment of TSC, and is likely to serve as an important supplementary feature for the current clinical diagnostic criteria for TSC.

Phosphorylation of S6 Protein as a Potential Biomarker in Surgically Treated Refractory Epilepsy.

The tuberous sclerosis complex (TSC), focal cortical dysplasia IIB (FCD IIB), and hemimegalencephaly (HME) exhibit similar molecular features that are dependent on the hyperactivation of the mTOR pathway. They are all associated with refractory epilepsy and the need for surgical resection with varying outcomes. The phosphorylated protein S6 (pS6) is a downstream target of mTOR, whose increased expression might indicate mTOR hyperactivation, but which is also present when there is no alteration in the pathway (such as in FCD type I). We have performed immunohistochemical marking and quantification of pS6 in resected brain specimens of 26 patients clinically and histologically diagnosed with TSC, FCD IIB, or HME and compared this data to a control group of 25 patients, to measure the extent of pS6 positivity and its correlation with clinical aspects. Our results suggest that pS6 may serve as a reliable biomarker in epilepsy and that a greater percentage of pS6 marking can relate to more severe forms of mTOR-dependent brain anomalies.

Interpreting the Tests of Focal Cortical Dysplasia for Epilepsy Surgery Referral.

OBJECTIVE: Focal cortical dysplasia (FCD) is a common cause of refractory, focal onset epilepsy in children. Interictal, scalp electroencephalograph (EEG) markers have been associated with these pathologies and epilepsy surgery may be an option for some patients. We aim to study how scalp EEG and magnetic resonance imaging (MRI) markers of FCD affect referral of these patients for surgical evaluation. METHODS: A single-center, retrospective review of children with focal onset epilepsy. Patients were included if they were between 1 month and 18 years of age, had focal onset seizures, prolonged scalp EEG monitoring, and an MRI conducted after 2 years of age. Statistics were carried out using the chi-squared and student's t-test, as well as a logistic regression model. RESULTS: Sixty-eight patients were included in the study. Thirty-seven of these patients were referred to a comprehensive pediatric epilepsy program (CPEP) for surgical evaluation, and of these 22% showed FCD EEG markers, 32% FCD MRI markers, and 10% had both. These markers were also present in patients not referred to a CPEP. The MRI markers were significantly associated with CPEP referral, whereas EEG markers were not. Neither marker type was associated with epilepsy surgery. CONCLUSION: This study found that children with focal onset epilepsy were more likely to be referred for surgical evaluation if they were medically refractory, or were diagnosed with FCD or tumor on MRI. Scalp EEG markers of FCD were not associated with CPEP referral. The online tool CASES may be a useful physician guide for identifying appropriate children for epilepsy surgery referral.

Interpréter les tests de détection de la dysplasie corticale focale en vue d'une évaluation préopératoire du traitement de l'épilepsie.Objectif: La dysplasie corticale focale (DCF) constitue une des causes communes des crises convulsives partielles réfractaires chez l'enfant. À la suite d'EEG effectués au niveau du cuir chevelu, des marqueurs de l'activité épileptique interictale ont été associés avec ce trouble pour lequel une intervention chirurgicale peut constituer, dans le cas de certains patients, une option. Nous voulons nous pencher sur la façon dont ces marqueurs et les marqueurs utilisés lors d'examens d'IRM pour la DCF peuvent affecter l'aiguillage de ces patients en vue d'une évaluation préopératoire. Méthodes: Dans un seul établissement hospitalier, nous avons effectué une analyse rétrospective de cas d'enfants chez qui sont apparues des crises convulsives partielles. Pour être inclus, les patients devaient être âgés de 1 mois à 18 ans, avoir été victimes de telles crises convulsives, avoir bénéficié de surveillance prolongée par EEG et avoir subi un examen d'IRM après l'âge de deux ans. Nous avons enfin effectué une analyse statistique à l'aide d'un modèle de régression logistique et des tests du X2 et de Student. Résultats: Au total, nous avons inclus soixante-huit patients dans cette étude. Trente-sept d'entre eux ont été redirigés vers un programme pédiatrique complet de traitement de l'épilepsie (comprehensive pediatric epilepsy program) en vue d'une évaluation préopératoire. Sur ces trente-sept patients, on a observé chez 22 % d'entre eux les marqueurs électroencéphalographiques associés à la DCF ; ce pourcentage atteignait 32 % dans le cas des marqueurs de la DCF utilisés en imagerie ; enfin, on a pu détecter ces deux types de marqueurs chez 10 % de ces trente-sept patients. Fait à souligner, ces marqueurs étaient aussi présents chez des patients n'ayant pas été orientés vers le type de programme cité ci-dessus. En outre, les marqueurs utilisés en imagerie se sont avérés étroitement associés au fait d'orienter des patients vers ce programme tandis que les marqueurs électroencéphalographiques ne l'étaient pas. Finalement, aucun de ces types de marqueurs n'a pu être associé à une intervention chirurgicale visant à traiter l'épilepsie. Conclusion: Cette étude a donc permis de constater que les enfants atteints de crises convulsives partielles étaient plus susceptibles d'être orientés en vue d'une évaluation préopératoire si leur trouble était de nature réfractaire ou s'ils avaient reçu un diagnostic de DCF ou de tumeur cancéreuse à la suite d'un examend'IRM. Les marqueurs électroencéphalographiques de la DCF n'ont pas été associés à un aiguillage vers un programme pédiatrique complet de traitement de l'épilepsie. Il se pourrait à cet égard que l'outil en ligne CASES soit un guide utile pour les médecins souhaitant identifier les enfants convenant à un aiguillage en vue d'un traitement chirurgical de l'épilepsie.

Dynamics of seizure-induced behavioral and autonomic arousal.

PURPOSE: Arousal is the most primitive, powerful instinct with survival benefit present in all vertebrates. Even though the arousal systems are classically viewed as "ascending" brainstem phenomena, there is a "descending" cortical feedback system that maintains consciousness. In this study, we provide electrophysiological confirmation that seizures localized to the anterior cingulum can behaviorally manifest as paroxysms of arousal from sleep. METHODS: Temporal dynamics of arousal induced by anterior cingulate seizures were analyzed by using multiple modalities including stereoelectroencephalography (phase lag index and phase amplitude coupling), lead-1 ECG (point-process heart rate variability analysis) and diffusion tractography (DTI). RESULTS: The ictal arousal was associated with an increase in synchronization in the alpha band and an increase in local theta or alpha-gamma phase-amplitude coupling. In comparison to seizures that lacked clinical manifestations, ictal arousal was associated with an increase in heart rate but not heart rate variability. Finally, DTI demonstrated degeneration in white fiber tracts passing between the anterior cingulum and anterior thalamus ipsilateral to the epileptogenic cortex. The patient underwent resection of the anterior cingulum, and histopathology confirmed focal cortical dysplasia type II. CONCLUSION: Anterior cingulate seizures inducing behavioral arousal have identifiable autonomic and EEG signatures.

A case of focal cortical dysplasia type Ib atypically showing reversible intensity changes on magnetic resonance imaging which could be affected by epileptic discharge activity.

Focal cortical dysplasia (FCD) was first described as a distinct neuropathological entity in 1971 by Taylor and colleagues. FCD is thought to be an embryological migration disorder and is thus considered a non-progressive, unchangeable disease throughout life. A 9-year-old right-handed boy was referred from a local hospital for medically intractable epileptic seizures. Serial magnetic resonance images (MRI) showed intensity changes that indicated exacerbation and remission. After presurgical evaluations including intracranial video-electroencephalogram monitoring, we performed a lesionectomy aided by MRI and epileptic focus resection. He has been free from seizures for more than 3 years. Neuropathological findings showed FCD type Ib. We surgically treated a patient with FCD, which showed MRI intensity changes indicating exacerbation and remission. Although FCD type Ib is generally invisible on MRI, in this patient, changes in intensity on MRI made FCD type Ib visible.

New developments in understanding focal cortical malformations.

PURPOSE OF REVIEW: Focal cortical dysplasias (FCDs) represent common cortical malformations that are frequently associated with epilepsy. They have so far not been well understood in terms of their molecular pathogenesis, and with respect to mechanisms of seizure emergence. RECENT FINDINGS: Several recent studies have succeeded in making significant advances in understanding the molecular genetics, in particular FCD type II. A second major advance has been the development of novel rodent models of FCDs that replicate a somatic mutation seen in humans, lead to a focal lesion, and recapitulate many phenotypic features of human FCDs. We will discuss these recent advances. SUMMARY: These advances promise significant advances in understanding the heterogeneity of FCDs at the molecular genetic level. They also promise a much better understanding of cell-intrinsic and network mechanisms underlying increased seizure susceptibility and altered cognition. Systematic studies utilizing the approaches summarized here promise to lead to specific strategies regarding when and how to treat specific subgroups of FCDs.

Epilepsy surgery for focal cortical dysplasia: Seizure and quality of life (QOLIE-89) outcomes.

AIM: Surgery for drug resistant epilepsy (DRE) with focal cortical dysplasia (FCD) often requires multiple non-invasive as well as invasive pre-surgical evaluations and innovative surgical strategies. There is limited data regarding surgical management of people with FCD as the underlying substrate for DRE among the low and middle-income countries (LAMIC) including India. METHODOLOGY: The presurgical evaluation, surgical strategy and outcome of 52 people who underwent resective surgery for DRE with FCD between January 2008 and December 2016 were analyzed. The 2011 classification proposed by Blumcke et al., was used for histo-pathological categorization. The Engel classification was used for defining the seizure outcome. The surgical outcome was correlated with the preoperative clinical presentation, video encephalogram (VEEG) recording, magnetic resonance imaging (MRI), invasive monitoring, surgical findings as well as histopathology and the quality of life in epilepsy (QOLIE)- 89 scores. RESULTS: Fifty-two patients underwent resective surgery for FCD (mean age at onset of seizure: 7.94 ± 6.23 years; duration of seizures prior to surgery: 12.95 ± 9.56 years; and, age at surgery: 20.88 ± 12.51 years). The following regional distribution was found; temporal-24 (language-13), frontal-15 (motor cortex- 5), parietal-5 (sensory cortex-4), occipital-1 and multilobar-7. Forty-seven percent of the cases had FCD in the right hemisphere and 53% had FCD in the left hemisphere. Invasive monitoring was performed for identification of the epileptogenic zone (EZ) as well as eloquent cortex in 7 cases and an intra-operative electro-corticography (ECoG) was used in 32 cases. Histopathology revealed the following distribution; FCD IA-4, IB- 1, IC-5, IIA-8, IIB-18, IIIA-13, IIIB -1, IIIC-1 and IIID-1. After a median follow up of 3.7 years after surgery, 84% of patients had Engel's Ia outcome. QOLIE-89 scores improved from 38.33 ± 4.7 (31.14-49.03) before surgery to 75.21 ± 8.44 (56.49-90.49) after surgery (P < 0.001). The younger age of the patient (<20 years) at surgery (P = 0.013), a lower pre-operative score (<9) on seizure severity scale (P = 0.012), focal discharges without propagation on ictal VEEG (P < 0.001), absence of acute post-operative seizures (P < 0.001) and Type II FCD (P = 0.045) were the significant predictors for a favorable seizure outcome. CONCLUSION: Surgical management of people with DRE and FCD is possible in countries with limited resources. Meticulous pre-surgical evaluation to localize the epileptogenic zone and complete resection of the focus and lesion can lead to the cure or control of epilepsy; and, improvement in the quality of life was observed along with seizure-free outcome.

Temporal lobe epilepsy and focal cortical dysplasia in children: A tip to find the abnormality.

OBJECTIVE: To demonstrate an association between magnetic resonance imaging (MRI) findings and pathologic characteristics in children who had surgery for medically refractory epilepsy due to focal cortical dysplasia (FCD). METHODS: We retrospectively studied 110 children who had epilepsy surgery. Twenty-seven patients with FCD were included. Thirteen had temporal lobe epilepsy (TLE) and 14 had extra-temporal lobe epilepsy (ETLE). Three patients had associated mesial temporal sclerosis. Preoperative 3T MRIs interleaved with nine controls were blindly re-reviewed and categorized according to signal alteration. Pathologic specimens were classified according to the 2011 International League Against Epilepsy (ILAE) classification and compared to MRI studies. RESULTS: Rates of pathology subtypes differed between TLE and ETLE (χ2 (3) = 8.57, p = 0.04). FCD type I was more frequent in TLE, whereas FCD type II was more frequent in ETLE. In the TLE group, nine patients had temporal tip abnormalities. They all exhibited gray-white matter blurring with decreased myelination and white matter hyperintense signal. Blurring involved the whole temporal tip, not just the area of dysplasia. These patients were less likely to demonstrate cortical thickening compared to those without temporal tip findings (χ2 (1) = 9.55, p = 0.002). Three of them had FCD Ib, three had FCD IIa, two had FCD IIIa, and one had FCD IIb; MRI features could not entirely distinguish between FCD subtypes. TLE patients showed more pronounced findings than ETLE on MRI (χ2 (1) = 11.95, p = 0.003, odds ratio [OR] 18.00). In all cases of FCD, isolated blurring was more likely to be associated with FCD II, whereas blurring with decreased myelination was seen with FCD I (χ2 (6) = 13.07, p = 0.042). SIGNIFICANCE: Our study described associations between MRI characteristics and pathology in children with FCD and offered a detailed analysis of temporal lobe tip abnormalities and FCD subtypes in children with TLE. These findings may contribute to the presurgical evaluation of patients with refractory epilepsy.

The diagnostic utility of 3D-ESI rotating and moving dipole methodology in the pre-surgical evaluation of MRI-negative childhood epilepsy due to focal cortical dysplasia.

OBJECTIVE: This study investigates whether a combined rotating dipole (RD) and moving dipole (MD) solution enhances three-dimensional electroencephalography (EEG) source imaging (3D-ESI) localization in magnetic resonance imaging (MRI)-negative pediatric patients with focal cortical dysplasia (FCD). METHODS: We retrospectively selected 14 MRI-negative patients with FCD from a cohort of 60 pediatric patients previously used to evaluate the diagnostic utility of 3D-ESI in epilepsy surgery. Patients were younger than 18 years at time of surgery and had at least 1 year of outcome data. RD and MD models were constructed for each interictal spike or sharp wave, and it was determined whether each inverse algorithm localized within the surgical resection cavity (SRC). We also compared the 3D-ESI findings and surgical outcome with positron emission tomography (PET) and ictal single photon emission computed tomography (iSPECT). RESULTS: RD analyses revealed a high concordance with the SRC (78.6%), particularly for temporal lobe resection (100.0%), and showed superior localization compared to PET and iSPECT, with the highest correlation in FCD type I and temporal lobe resection. Furthermore, the RD method was superior to iSPECT in FCD type II cases and to PET in extratemporal resections. RD and MD results were comparable, but in 18.2% of patients with FCD type I with localizing RDs, the MD solution was only partially within the SRC; in all of these patients 3D-ESI also correlated with superior surgical outcome compared to PET and iSPECT, especially when RD and MD solutions were analyzed together. SIGNIFICANCE: 3D-ESI in MRI-negative cases showed superior localization compared to iSPECT or PET, especially in FCD type I and temporal lobe epilepsy, and correlated with superior surgical outcome compared to iSPECT and PET at 1 year and 2 years postoperatively, especially when RD and MD solutions were analyzed together. These findings suggest that 3D-ESI based on a combined RD-MD solution improves surgical accuracy in MRI-negative patients with FCD.

Desmoplastic infantile ganglioglioma with focal cortical dysplasia: A rare double pathology in an infant with history of seizures.

We describe an extremely rare case of double pathology arising in an infant girl presenting with a history of intractable seizures, delayed milestones and enlarging head. The pathology included desmoplastic infantile ganglioglioma (DIG) and extensive focal cortical dysplasia in the overlying cortex. While tumors such as ganglioglioma have been commonly described to occur as concomitant pathology with cortical dysplasia, DIG in such an association has not been described in the literature. As DIG are voluminous supratentorial tumors, awareness about such an association is pertinent for correct diagnosis.

Long-term seizure outcome in 211 patients with focal cortical dysplasia.

OBJECTIVE: Focal cortical dysplasia (FCD) is currently recognized as the most common cause of neocortical pharmacoresistant epilepsy. Epilepsy surgery has become an increasingly successful treatment option. Herein, the largest patient cohort reported to date is analyzed regarding long-term outcome and factors relevant for long-term seizure control. METHODS: Two hundred eleven children and adults undergoing epilepsy surgery for histologically proven FCD and a follow-up period of 2-12 years were analyzed regarding the longitudinal course of seizure control, effects of FCD type, localization, magnetic resonance imaging (MRI), timing of surgery, and postoperative antiepileptic treatment. RESULTS: After 1 year, Engel class I outcome was achieved in 65% of patients and the percentage of seizure-free patients remained stable over the following (up to 12) years. Complete resection of the assumed epileptogenic area, lower age at surgery, and unilobar localization were positive prognostic indicators of long-term seizure freedom. Seizure recurrence was 12% after the first year, whereas 8% achieved late seizure freedom either following additional introduction of antiepileptic drugs (AEDs) (4%), a reoperation (2%), or a running down phenomenon (2%). Thirty-nine percent of patients had a reduction of AED from polytherapy to monotherapy or a complete cessation of AED treatment. Late seizure relapse was seen in nine patients during reduction of AEDs (i.e., in 12% of all patients with AED tapering); in four of them seizures persisted after reestablishment of antiepileptic medication. SIGNIFICANCE: Postoperative long-term seizure outcome was favorable in patients with FCD and remained stable in 80% of patients after the first postoperative year. Several preoperative factors revealed to be predictive for the postoperative outcome and may help in the preoperative counseling of patients with FCD and in the selection of ideal candidates for epilepsy surgery.

Expression of glutamine synthetase in balloon cells: a basis of their antiepileptic role?

Glutamine synthetase is an enzyme involved in the clearance of glutamate, the most potent excitatory neurotransmitter. We studied the immunohistochemical expression of glutamine synthetase in neocortical samples from 5 children who underwent surgery for pharmacoresistant epilepsy and a histological diagnosis of focal cortical dysplasia IIb. In all cases, balloon cells, but not dysmorphic neurons, were immunopositive for glutamine synthetase. This finding suggests that balloon cells can be involved in the neutralization of glutamate and play a protective anti-seizure role.

Post-surgical outcome for epilepsy associated with type I focal cortical dysplasia subtypes.

Focal cortical dysplasias are a well-recognized cause of medically intractable seizures. The clinical relevance of certain subgroups of the International League Against Epilepsy (ILAE) classification scheme remains to be determined. The aim of the present work is to assess the effect of the focal cortical dysplasia type Ib and Ic histologic subtypes on surgical outcome with respect to seizure frequency. This study also provides an opportunity to compare the predictive value of the ILAE and Palmini et al classification schemes with regard to the type I focal cortical dysplasias. We retrospectively reviewed 91 focal cortical dysplasia patients (55% female; median age: 19 years (interquartile range 8-34); median seizure duration: 108 months (interquartile range 36-204)) with chronic epilepsy who underwent surgery. We compared the pathological subtypes, evaluating the patients' post-surgical outcome with respect to seizure frequency according to the Engel's classification and the ILAE outcome classification. Both the ILAE classification scheme and Palmini et al classification scheme were utilized to classify the histologic subtype. Using χ(2) and Fisher's exact tests, we compared the post-surgical outcomes among these groups. Of the 91 patients, there were 50 patients with ILAE focal cortical dysplasia type Ib, 41 with ILAE focal cortical dysplasia type Ic, 63 with Palmini et al focal cortical dysplasia type IA, and 28 with Palmini et al focal cortical dysplasia type IB. After surgery, 44 patients (48%) were seizure-free. Crude analysis revealed no significant difference between patients with subtypes of ILAE focal cortical dysplasia type I or Palmini et al focal cortical dysplasia type I concerning postoperative outcome according to the Engel and ILAE scoring systems on seizure frequency. Our findings revealed no significant difference concerning surgical outcome with respect to seizure frequency for the histologic subtypes of ILAE focal cortical dysplasia type I (Ib vs Ic) or Palmini et al focal cortical dysplasia type I (IA vs IB). In isolation, the histologic subtype of focal cortical dysplasia type I does not appear predictive of postoperative outcome.

Clinical characteristics, pathological features and surgical outcomes of focal cortical dysplasia (FCD) type II: correlation with pathological subtypes.

Focal cortical dysplasia (FCD) type II is a major cause of drug-resistant epilepsy. In order to gain insight into the possible correlations between FCD II pathological pattern and different clinical characteristics (including clinical information, imaging characteristics and surgical outcomes), different clinicopathological characteristics in two types of FCD II were analyzed (especially in FCD IIb). The mean age of seizure onset and disease duration of 78 patients was 11.0 and 11.2 years, respectively. Patients with FCD type IIb had earlier seizure onset compared with those with FCD type IIa. Pathological subtype IIb was predominantly in frontal lobe and subtype IIa was predominantly seen in temporal. Type IIb demonstrated significantly more signal abnormalities in fluid attenuated inversion recovery (FLAIR) images and T2 images than Type IIa. The rate of satisfactory seizure outcome was 67.64 % in the FCD IIa group, while relative higher, 88.63 %, in the FCD IIb group. All these characteristics may assist in their earlier diagnosis and improve the predictability of surgical management.

Somatic mutations involving TSC 1 and TSC2 genes in two children with focal cortical dysplasia.

BACKGROUND: The role of PI3K/AKT/mTOR pathway hyperactivation in localized brain overgrowth is evolving. We describe two patients with focal cortical dysplasia (FCD) who demonstrated somatic mutations in TSC1 and TSC2 genes in the dysplastic brain tissue but not peripheral blood. METHODS: Paired whole-exome sequencing was performed on genomic DNA extracted from blood and excised brain tissue in two children with FCD who underwent excision of dysplastic tissue. RESULTS: Patient 1, a 14-year boy, had drug-resistant focal epilepsy with onset at 20 months. His brain MRI showed abnormalities suggestive of FCD in the left superior and middle frontal lobes. Patient 2 presented at the age of 10 years with pharmaco-resistant focal epilepsy (onset at six years). His MRI suggested FCD in the left insular lobe. Both patients underwent surgical excision of FCD, and excised tissues were pathologically confirmed to have type IIb FCD. For patient 1, a missense mutation (c.64C > T; p.Arg22Trp) was detected in the TSC1 gene in DNA of dysplastic brain tissue but not peripheral blood lymphocytes. Similarly, for patient 2, a frameshift mutation (c.4258_4261delCAGT; p.Ser1420GlyfsTer55) in the TSC2 gene was identified in the brain tissue but not blood. Both gene variants are likely pathogenic and cause mTOR pathway activation. CONCLUSION: Our report of TSC1/TSC2 somatic mutations in patients with non-syndromic FCD suggests that localized hyperactivation of the mTOR pathway can cause focal malformations during cortical development and presents pharmacological targets for precision therapy in FCD management.

Focal thalamocortical circuit abnormalities in sleep related epilepsy caused by focal cortical dysplasia type II.

Purpose To investigate the variations of the thalamocortical circuit between the focal cortical dysplasia (FCD) type II patients with sleep-related epilepsy (SRE) and those without SRE (non-SRE). Methods Patients with epilepsy who had histologically proven FCD type II were enrolled. Those without diffusion tensor image and 3-dimensional (3D) T1 MRI sequences were excluded. Thalamocortical structural connectivity to lesion and non-lesion regions was quantified using probabilistic tractography. Fractional anisotropy (FA) and mean diffusivity (MD) were computed. Results A total of 30 consecutive patients were included. Among them, 18 patients (60%) had SRE. Analysis of covariance showed that smaller lesion size was significantly associated with SRE (p=0.048). Compared to patients with non-SRE, patients with SRE showed a significant decrease in FA of thalamocortical projections to the lesion region (p=0.007). No difference was observed in the thalamocortical connectivity to the non-lesion region between patients with SRE and non-SRE. Among the patients with SRE, a significant decrease in FA of thalamocortical projections to the lesion region was noted compared with the contralateral homotopic non-lesion region (p=0.026). Conclusion The data provide evidence of disparity in thalamocortical projections to the lesion regions between SRE and non-SRE. This might indicate the underlying pathophysiology or neuroanatomical substrates of SRE related to the FCD type II.