Early Clinical Predictors of Autism Spectrum Disorder in Infants with Tuberous Sclerosis Complex: Results from the EPISTOP Study

Risk Factors for Psychiatric Disorders in Pediatric Patients with Tuberous Sclerosis Complex

To identify and evaluate risk factors for psychiatric disorders in pediatric patients with tuberous sclerosis complex (TSC).We recruited 121 children with TSC from the Hangzhou Children's Hospital between April 2021 and December 2023. Four clinical psychiatric scales were used to screen and diagnose the psychiatric comorbidities of TSC: the autism behavior checklist, the SNAP-IV scale, and the self-rating anxiety and depression scales. Risk factors related to each psychiatric disorder were analyzed using univariate and multivariate regression analyses.Comorbid psychiatric disorders were found in 70 (57.85%) children: 51 (42.15%) cases had autism spectrum disorder (ASD), 49 (40.50%) cases had attention-deficit hyperactivity disorder (ADHD), 17 (14.05%) cases had anxiety, and 14 (11.57%) cases had depression. Uni- and multivariate logistic regression analysis revealed that seizure frequency (>1/month; OR = 6.206, P = 0.021), use of anti-seizure medications (≥ 2 types; OR = 118.869, P = 0.003), infantile spasms (OR = 25.748, P = 0.000), ADHD (OR = 11.170, P = 0.001), and intellectual disability (OR = 32.131, P = 0.001) were risk factors for TSC children with ASD; ASD was the only risk factor for occurrence of ADHD (OR = 7.302, P = 0.022). Seizure duration (≥ 2 years; OR = 56.200, P = 0.036) and seizure frequency (>1/month; OR = 25.855, P = 0.027) were closely related to occurrence of anxiety and/or depression disorders in pediatric patients with TSC.The study results showed that psychiatric comorbidities of children with TSC had a high incidence and risk factors. The study provides new insights into the diagnosis and treatment of comorbid psychiatric disorders in pediatric patients with TSC.

Neuropsychiatric disorders in Chinese pediatric tuberous sclerosis complex patients associated with drug-resistant epilepsy: A TAND checklist-based survey

Tuberous sclerosis complex (TSC) is an autosomal-dominant genetic disorder frequently accompanied by neuropsychiatric disorders, especially in patients who have drug-resistant epilepsy (DRE). This study aimed to evaluate the distribution of neuropsychiatric disorders in Chinese children with TSC-related epilepsy using the TAND (Tuberous Sclerosis Complex Associated Neuropsychiatric Disorders) checklist, comparing those with DRE to those achieving seizure freedom. A total of 47 children, aged 6 to 18 years, diagnosed with TSC at Peking University People's Hospital, participated in this cross-sectional study. All participants met the latest diagnostic criteria for TSC. Based on the definition of drug-resistant epilepsy, participants were categorized into DRE group and seizure-free group. Neurodevelopmental disorders were evaluated using the TAND checklist. The study found that 66 % of participants exhibited varying degrees of intellectual disability, with the DRE group demonstrating significantly poorer performance in intelligence, behavior, neuropsychological, and learning skills compared to the seizure-free group. The DRE group also had higher rates of attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD), alongside greater impairments in psychosocial functioning. This study indicates that DRE is strongly associated with neuropsychiatric development in children with TSC, but also that all children with TSC are at increased risk of TAND. Our findings highlight the importance of regular assessment and intervention to support TAND and improve quality of life in this vulnerable group.

Mechanistic strategies for secondary prevention of developmental and epileptic encephalopathy in children with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder caused by pathogenic variants in TSC1 or TSC2, leading to mTOR pathway dysregulation and a spectrum of systemic and neurological manifestations. Tuberous Sclerosis Complex (TSC) is a multisystem genetic disorder frequently associated with early-onset, drug-resistant epilepsy, intellectual disability, and autism spectrum disorder-collectively known as TSC-associated developmental and epileptic encephalopathy (DEE). Advances in prenatal diagnostics and biomarker research now enable presymptomatic identification of high-risk infants. This review aims to synthesize current evidence on biomarker-informed, mechanism-based strategies for secondary prevention of DEE in TSC, offering a framework for personalized early interventions. Biomarkers, such as interictal epileptiform discharges, pathogenic TSC2 variants, and advanced neuroimaging metrics, predict epilepsy risk and neurodevelopmental trajectories. Preventive approaches include early initiation of vigabatrin and mTOR inhibitors, which show potential in reducing epilepsy severity and improving outcomes. Emerging strategies, including gene therapy, multi-omic profiling, and environmental enrichment, offer promise for disease modification. By linking predictive biomarkers to disease-modifying strategies, this review outlines a proactive and personalised approach to prevent or mitigate TSC-associated DEE. These insights help advance clinical decision-making and promote a shift toward precision prevention in paediatric epilepsy.

Intellectual disability and autistic behavior and their modifying factors in children with tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is classified among developmental epileptic encephalopathies, where epilepsy is often associated with comorbidities such as intellectual disability and autistic behavior. The recently introduced term TAND (TSC-associated neuropsychiatric disorders) encompasses the wide range of cognitive, behavioral, psychiatric, and psychosocial manifestations seen in TSC. The severity of these comorbidities is influenced by several factors, including the TSC1/TSC2 genotype, the age of epilepsy onset, the number, volume and type of cortical tubers, the interval between epilepsy onset and treatment initiation, and the presence of infantile spasms, hypsarrhythmia, or drug-resistant epilepsy. Clinical, genetic, EEG, and neuroimaging biomarkers enable the early identification of infants at high risk of developing intellectual disability or autism spectrum disorder. Early preventive intervention targeting seizures and tailored strategies during a sensitive developmental window may modify these contributing factors, leading to improved neurodevelopmental outcomes in infants with TSC.

Long-term neuropsychologic outcome of pre-emptive mTOR inhibitor treatment in children with tuberous sclerosis complex (TSC) under 4 months of age (PROTECT), a two-arm, randomized, observer-blind, controlled phase IIb national multicentre clinical trial: study protocol

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder affecting multiple organ systems, with a prevalence of 1:6,760-1:13,520 live births in Germany. On the molecular level, TSC is caused by heterozygous loss-of-function variants in either of the genes TSC1 or TSC2, encoding the Tuberin-Hamartin complex, which acts as a critical upstream suppressor of the mammalian target of rapamycin (mTOR), a key signaling pathway controlling cellular growth and metabolism. Despite the therapeutic success of mTOR inhibition in treating TSC-associated manifestations, studies with mTOR inhibitors in children with TSC above two years of age have failed to demonstrate beneficial effects on disease-related neuropsychological deficits. It has thus been hypothesized, that the critical time window for mTOR inhibitors may lie in early infancy, before TSC-related symptoms such as early-onset epilepsy and infantile spasms as sign of disruptive brain maturation occur. No controlled prospective clinical trials have evaluated the effect of pre-symptomatic mTOR inhibitor therapy on neuropsychological manifestations in TSC patients under two years of age.

METHODS

This two-arm, randomized, observer-blind, phase IIb national multicenter clinical trial aims at investigating the long-term neuropsychologic outcomes of pre-emptive mTOR inhibitor treatment in children diagnosed with TSC under four months of age. Sixty participants will be allocated to the trial with a 1:1 randomization ratio. The primary endpoint will be the neuropsychological outcome assessed by the cognitive scale of the Bayley Scales of Infant and Toddler Development III at 24 months of age compared to Standard of Care. Secondary endpoints include neuropsychologic outcomes at 12 months of age, seizure frequency, cardiac and cerebral tumor load, and safety assessments. Inclusion criteria are a definite TSC diagnosis and an age below four months at enrolment. The investigational medicinal product is sirolimus (Rapamune®), administered orally based on body surface area and surveilled by pharmacokinetic measurements, starting within the first four months of life and continuing until the second birthday.

CONCLUSION

This study addresses a critical gap in understanding the impact of pre-emptive mTOR inhibitor therapy on neuropsychologic outcomes in young TSC patients, aiming to improve overall patient outcomes and quality of life. EUCT number: 2022-502332-39-00, Registered 22/06/2023, https://euclinicaltrials.eu/search-for-clinical-trials/?lang=en&EUCT=2022-502332-39-00.

Prenatal mTOR Inhibitors in Tuberous Sclerosis Complex: Current Insights and Future Directions

Background: Tuberous sclerosis complex (TSC) can present prenatally, often with cardiac rhabdomyomas, which, if large, may cause complications such as hydrops fetalis and reduced cardiac output. Prenatal treatment of these lesions with mTOR inhibitors, approved for other TSC manifestations, is under investigation. We hypothesize that mTOR inhibitors could help manage or prevent other TSC-related conditions, particularly neurological issues like epilepsy and CNS lesions, potentially improving neurodevelopmental outcomes. However, the safety of prenatal mTOR treatment remains a concern, especially for foetal development, and limited data are available on neurological outcomes. Methods: We conducted a literature review using PubMed, EMBASE, and Cochrane CENTRAL, focusing on studies involving mTOR inhibitors for prenatal TSC management. The search included case reports and series involving pregnant women diagnosed with TSC or early manifestations like cardiac rhabdomyomas. Keywords included "mTOR Inhibitor", "Rapamycin", "tuberous sclerosis complex", "prenatal", and "rhabdomyoma". Results: Three prenatal mouse studies and eight papers reporting on ten pregnant women treated with mTOR inhibitors were identified. Conclusions: The literature confirms that prenatal mTOR inhibitors may reduce cardiac rhabdomyomas. However, further studies are needed to explore their broader potential, particularly in preventing neurological complications, while carefully considering their impact on intrauterine growth and neurodevelopment.

Is tuberous sclerosis complex-associated autism a preventable and treatable disorder?

BACKGROUND

Tuberous sclerosis complex (TSC) is a genetic disorder caused by inactivating mutations in the TSC1 and TSC2 genes, causing overactivation of the mechanistic (previously referred to as mammalian) target of rapamycin (mTOR) signaling pathway in fetal life. The mTOR pathway plays a crucial role in several brain processes leading to TSC-related epilepsy, intellectual disability, and autism spectrum disorder (ASD). Pre-natal or early post-natal diagnosis of TSC is now possible in a growing number of pre-symptomatic infants.

DATA SOURCES

We searched PubMed for peer-reviewed publications published between January 2010 and April 2023 with the terms "tuberous sclerosis", "autism", or "autism spectrum disorder"," animal models", "preclinical studies", "neurobiology", and "treatment".

RESULTS

Prospective studies have highlighted that developmental trajectories in TSC infants who were later diagnosed with ASD already show motor, visual and social communication skills in the first year of life delays. Reliable genetic, cellular, electroencephalography and magnetic resonance imaging biomarkers can identify pre-symptomatic TSC infants at high risk for having autism and epilepsy.

CONCLUSIONS

Preventing epilepsy or improving therapy for seizures associated with prompt and tailored treatment strategies for autism in a sensitive developmental time window could have the potential to mitigate autistic symptoms in infants with TSC.

A single-center observational study on long-term neurodevelopmental outcomes in children with tuberous sclerosis complex

BACKGROUND

Tuberous sclerosis complex (TSC) is a rare multisystem disorder caused by mutations in the TSC1 or TSC2 gene. More than 90% of patients with TSC develop neurological and/or neuropsychiatric manifestations. The aim of the present study was to determine the developmental and cognitive long-term outcomes of pediatric TSC patients.

METHODS

This cross-sectional, monocenter study included pediatric TSC patients who received multidisciplinary long-term care with a last visit between 2005 and 2019. Neurological manifestations and cognitive development (BSID, K-ABC) were analyzed in relation to age and type of mutation.

RESULTS

Thirty-five patients aged 13.5 ± 7.8 years were included in the study. Diagnosis was confirmed genetically in 65.7% of patients (TSC1, 26.1%; TSC2, 65.2%; NMI, 8.7%). Mean age at diagnosis was 1.3 ± 3.5 years; 74.3% of the patients had been diagnosed within the first year of life due to seizures (62.9%) or/and cardiac rhabdomyomas (28.6%). The most common TSC manifestations included structural brain lesions (cortical tubers, 91.4%; subependymal nodules, 82.9%), epilepsy (85.7%), and cardiac rhabdomyomas (62.9%). Mean age at seizure onset was 1.5 ± 2.3 years, with onset in 80.0% of patients within the first two years of life. Infantile spasms, which were the first seizure type in 23.3% of the patients, developed earlier (0.6 ± 0.4 years) than focal seizures (1.8 ± 2.5 years). Refractory epilepsy was present in 21 (70.0%) patients, mild or severe intellectual impairment in 66.6%, and autism spectrum disorders in 11.4%. Severe cognitive impairment (33.3%) was significantly associated with epilepsy type and age at seizure onset (p < 0.05).

CONCLUSIONS

The results emphasized the phenotypic variability of pediatric-onset TSC and the high rate of neurological and neuropsychiatric morbidity. Early-onset refractory epilepsy was associated with impaired cognitive development. Children of all ages with TSC require multidisciplinary long-term care and individual early-intervention programs.

Updated clinical recommendations for the management of tuberous sclerosis complex associated epilepsy

Children with tuberous sclerosis complex (TSC), may experience a variety of seizure types in the first year of life, most often focal seizure sand epileptic spasms. Drug resistance is seen early in many patients, and the management of TSC associated epilepsy remain a major challenge for clinicians. In 2018 clinical recommendations for the management of TSC associated epilepsy were published by a panel of European experts. In the last five years considerable progress has been made in understanding the neurobiology of epileptogenesis and three interventional randomized controlled trials have changed the therapeutic approach for the management of TSC associated epilepsy. Pre-symptomatic treatment with vigabatrin may delay seizure onset, may reduce seizure severity and reduce the risk of epileptic encephalopathy. The efficacy of mTOR inhibition with adjunctive everolimus was documented in patients with TSC associated refractory seizures and cannabidiol could be another therapeutic option. Epilepsy surgery has significantly improved seizure outcome in selected patients and should be considered early in all patients with drug resistant epilepsy. There is a need to identify patients who may have a higher risk of developing epilepsy and autism spectrum disorder (ASD). In the recent years significant progress has been made owing to the early identification of risk factors for the development of drug-resistant epilepsy. Better understanding of the mechanism underlying epileptogenesis may improve the management for TSC-related epilepsy. Developmental neurobiology and neuropathology give opportunities for the implementation of concepts related to clinical findings, and an early genetic diagnosis and use of EEG and MRI biomarkers may improve the development of pre-symptomatic and disease-modifying strategies.

Understanding speech and language in tuberous sclerosis complex

Tuberous Sclerosis Complex (TSC), is a neurocutaneous disorder, associated with a high prevalence of autism spectrum disorder (ASD; ∼50% of individuals). As TSC is a leading cause of syndromic ASD, understanding language development in this population would not only be important for individuals with TSC but may also have implications for those with other causes of syndromic and idiopathic ASD. In this mini review, we consider what is known about language development in this population and how speech and language in TSC are related to ASD. Although up to 70% of individuals with TSC report language difficulties, much of the limited research to date on language in TSC has been based on summary scores from standardized assessments. Missing is a detailed understanding of the mechanisms driving speech and language in TSC and how they relate to ASD. Here, we review recent work suggesting that canonical babbling and volubility-two precursors of language development that predict the emergence of speech and are delayed in infants with idiopathic ASD-are also delayed in infants with TSC. We then look to the broader literature on language development to identify other early precursors of language development that tend to be delayed in children with autism as a guide for future research on speech and language in TSC. We argue that vocal turn-taking, shared attention, and fast mapping are three such skills that can provide important information about how speech and language develop in TSC and where potential delays come from. The overall goal of this line of research is to not only illuminate the trajectory of language in TSC with and without ASD, but to ultimately find strategies for earlier recognition and treatment of the pervasive language difficulties in this population.

Heterogeneity of Autism Characteristics in Genetic Syndromes: Key Considerations for Assessment and Support

Purpose of Review

Elevated prevalence of autism characteristics is reported in genetic syndromes associated with intellectual disability. This review summarises recent evidence on the behavioural heterogeneity of autism in the following syndromes: Fragile X, Cornelia de Lange, Williams, Prader-Willi, Angelman, Down, Smith-Magenis, and tuberous sclerosis complex. Key considerations for assessment and support are discussed.

Recent Findings

The profile and developmental trajectory of autism-related behaviour in these syndromes indicate some degree of syndrome specificity which may interact with broader behavioural phenotypes (e.g. hypersociability), intellectual disability, and mental health (e.g. anxiety). Genetic subtype and co-occurring epilepsy within syndromes contribute to increased significance of autism characteristics. Autism-related strengths and challenges are likely to be overlooked or misunderstood using existing screening/diagnostic tools and criteria, which lack sensitivity and specificity within these populations.

Summary

Autism characteristics are highly heterogeneous across genetic syndromes and often distinguishable from non-syndromic autism. Autism diagnostic assessment practices in this population should be tailored to specific syndromes. Service provisions must begin to prioritise needs-led support.

Identification of a Novel TSC2 c.170G>A Missense Variant: A Case Report and Elaboration on the Yield of Targeted Options against Tuberous Sclerosis Complex Manifestations

BACKGROUND

Tuberous sclerosis complex (TSC) is a rare genetic disease that affects multiple organs and affects the quality of life. Mutations in TSC1 and TSC2 genes are causing dysregulations in the mammalian target of the rapamycin (mTOR) pathway, inducing mostly benign but also malignant tumors, including renal cell carcinoma (RCC). The diagnosis of TSC, based on established clinical and genetic criteria, is essential for the optimal surveillance and management of patients.

CASE PRESENTATION

With the current report, we present the case of two sisters who were consequently diagnosed with early-stage chromophobe-like RCC, possibly familial given their young age. The younger sister also had a previous diagnosis of differentiated thyroid carcinoma, for which she had been treated properly. Genetic testing of both revealed the same heterozygous TSC2 variant that is currently regarded as a variant of unknown significance, while both patients did not fulfill the clinical criteria for the diagnosis of TSC. Owing to these data, we opted to manage and surveil both sisters as TSC patients, while we also considered the specific TSC2 variant to be pathogenic - but of low penetrance - based on clinical judgment and functional analyses. Furthermore, we discussed the implementation of mTOR inhibitors for the treatment of TSC complications.

CONCLUSION

As novel pathogenic variants of TSC genes are constantly being explored, the identification of TSC variants of unknown significance in combination with absent clinical diagnostic criteria cannot exclude a TSC diagnosis. We support the implementation of clinical judgment in assisting the diagnosis of TSC, as well as the enrollment of patients in clinical trials due to the rarity of the disease.

Epilepsy and Language Development in 8–36-Month-Old Toddlers with Tuberous Sclerosis Complex

This paper aimed to assess language development in infants and toddlers with tuberous sclerosis complex (TSC) and epilepsy, which increase the risk of autism spectrum disorder. We assessed language development in 61 patients with TSC at 8–36 months using a standardized Speech Development and Communication Inventory tool. The results showed differences in outcomes due to the duration of the seizures and the number of drugs (pFDR = 0.007 **—pFDR = 0.037 *). Children with TSC with longer epilepsy duration and receiving more antiepileptic drugs have a greater risk of language development delay.

miRNAs and isomiRs: Serum-Based Biomarkers for the Development of Intellectual Disability and Autism Spectrum Disorder in Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is a rare multi-system genetic disorder characterized by a high incidence of epilepsy and neuropsychiatric manifestations known as tuberous-sclerosis-associated neuropsychiatric disorders (TANDs), including autism spectrum disorder (ASD) and intellectual disability (ID). MicroRNAs (miRNAs) are small regulatory non-coding RNAs that regulate the expression of more than 60% of all protein-coding genes in humans and have been reported to be dysregulated in several diseases, including TSC. In the current study, RNA sequencing analysis was performed to define the miRNA and isoform (isomiR) expression patterns in serum. A Receiver Operating Characteristic (ROC) curve analysis was used to identify circulating molecular biomarkers, miRNAs, and isomiRs, able to discriminate the development of neuropsychiatric comorbidity, either ASD, ID, or ASD + ID, in patients with TSC. Part of our bioinformatics predictions was verified with RT-qPCR performed on RNA isolated from patients’ serum. Our results support the notion that circulating miRNAs and isomiRs have the potential to aid standard clinical testing in the early risk assessment of ASD and ID development in TSC patients.

Identifying biomarkers for epilepsy after cerebral malaria in Zambian children: rationale and design of a prospective observational study

INTRODUCTION

Malaria affecting the central nervous system (CM) is a major contributor to paediatric epilepsy in resource-poor settings, with 10%-16% of survivors developing epilepsy within 2 years of infection. Despite high risk for post-malaria epilepsy (PME), biomarkers indicating which CM survivors will develop epilepsy are absent. Such biomarkers are essential to identify those at highest risk who might benefit most from close surveillance and/or preventive treatments. Electroencephalography (EEG) contains signals (specifically gamma frequency activity), which are correlated with higher risk of PME and provide a biomarker for the development of epilepsy. We propose to study the sensitivity of quantitative and qualitative EEG metrics in predicting PME, and the potential increased sensitivity of this measure with additional clinical metrics. Our goal is to develop a predictive PME index composed of EEG and clinical history metrics that are highly feasible to obtain in low-resourced regions.

METHODS AND ANALYSES

This prospective observational study being conducted in Eastern Zambia will recruit 250 children aged 6 months to 11 years presenting with acute CM and follow them for two years. Children with pre-existing epilepsy diagnoses will be excluded. Outcome measures will include qualitative and quantitative analysis of routine EEG recordings, as well as clinical metrics in the acute and subacute period, including histidine-rich protein 2 levels of parasite burden, depth and length of coma, presence and severity of acute seizures, presence of hypoglycaemia, maximum temperature and 1-month post-CM neurodevelopmental assessment scores. We will test the performance of these EEG and clinical metrics in predicting development of epilepsy through multivariate logistic regression analyses.

ETHICS AND DISSEMINATION

This study has been approved by the Boston Children's Hospital Institutional Review Board, University of Zambia Biomedical Research Ethics Committee, and National Health Research Authority of Zambia. Results will be disseminated locally in Zambia followed by publication in international, open access, peer-reviewed journals when feasible.

Postnatal Cytomegalovirus Infection May Increase the Susceptibility of Tuberous Sclerosis Complex to Autism Spectrum Disorders

Autism spectrum disorder (ASD), a highly hereditary and heterogeneous neurodevelopmental disorder, is influenced by genetic and environmental factors. Tuberous sclerosis complex (TSC) is a common syndrome associated with ASD. Cytomegalovirus (CMV) infection is an environmental risk factor for ASD. The similarities in pathological and mechanistic pathways of TSC and CMV intrigued us to investigate whether CMV and TSC interacted in ASD's occurrence. We detected CMV IgG seroprevalence of 308 TSC patients from our prospective cohort (September 2011 to March 2021) and 93 healthy children by magnetic particle indirect chemiluminescence immunoassay. A total of 206 TSC patients enrolled were divided into ASD and non-ASD groups, and the relationship between ASD and CMV seroprevalence was analyzed. Nested PCR and Western blot were used to detect CMV DNAs and proteins in cortical malformations of seven TSC patients with and without ASD. No difference was found in CMV seroprevalence between TSC patients and healthy children (74.0% versus 72.0%, P = 0.704). Univariate analysis showed the seroprevalence in TSC patients with ASD was higher than that in TSC patients without ASD (89.2% versus 75.1%, P = 0.063), and multifactorial analysis showed that CMV seroprevalence was a risk factor for ASD in TSC patients (OR = 3.976, 95% CI = 1.093 to 14.454). Moreover, CMV was more likely to be detected in the cortical malformations in TSC patients with ASD but not in those without ASD. The findings demonstrated that CMV may increase the susceptibility of TSC to ASD. IMPORTANCE CMV is an environmental risk factor for ASD, but its role in syndromic autism with known genetic etiology has been rarely studied. The pathogenesis of ASD is related to the interaction between environmental and genetic factors. This study demonstrated that CMV can contribute to the occurrence of ASD related to TSC, a common genetic syndrome associated with ASD. Our findings provided support for the theory of gene-environment interaction (G × E) in pathogenesis of ASD and a new perspective for the prevention and therapy for TSC related ASD.

Shared Etiology in Autism Spectrum Disorder and Epilepsy with Functional Disability

Autism spectrum disorders and epilepsies are heterogeneous human disorders that have miscellaneous etiologies and pathophysiology. There is considerable risk of frequent epilepsy in autism that facilitates amplified morbidity and mortality. Several biological pathways appear to be involved in disease progression, including gene transcription regulation, cellular growth, synaptic channel function, and maintenance of synaptic structure. Here, abnormalities in excitatory/inhibitory (E/I) balance ratio are reviewed along with part of an epileptiform activity that may drive both overconnectivity and genetic disorders where autism spectrum disorders and epilepsy frequently co-occur. The most current ideas concerning common etiological and molecular mechanisms for co-occurrence of both autism spectrum disorders and epilepsy are discussed along with the powerful pharmacological therapies that protect the cognition and behavior of patients. Better understanding is necessary to identify a biological mechanism that might lead to possible treatments for these neurological disorders.

Electrophysiological and Behavioral Evidence for Hyper- and Hyposensitivity in Rare Genetic Syndromes Associated with Autism

Our study reviewed abnormalities in spontaneous, as well as event-related, brain activity in syndromes with a known genetic underpinning that are associated with autistic symptomatology. Based on behavioral and neurophysiological evidence, we tentatively subdivided the syndromes on primarily hyper-sensitive (Fragile X, Angelman) and hypo-sensitive (Phelan-McDermid, Rett, Tuberous Sclerosis, Neurofibromatosis 1), pointing to the way of segregation of heterogeneous idiopathic ASD, that includes both hyper-sensitive and hypo-sensitive individuals. This segmentation links abnormalities in different genes, such as FMR1, UBE3A, GABRB3, GABRA5, GABRG3, SHANK3, MECP2, TSC1, TSC2, and NF1, that are causative to the above-mentioned syndromes and associated with synaptic transmission and cell growth, as well as with translational and transcriptional regulation and with sensory sensitivity. Excitation/inhibition imbalance related to GABAergic signaling, and the interplay of tonic and phasic inhibition in different brain regions might underlie this relationship. However, more research is needed. As most genetic syndromes are very rare, future investigations in this field will benefit from multi-site collaboration with a common protocol for electrophysiological and event-related potential (EEG/ERP) research that should include an investigation into all modalities and stages of sensory processing, as well as potential biomarkers of GABAergic signaling (such as 40-Hz ASSR).

Evolution of electroencephalogram in infants with tuberous sclerosis complex and neurodevelopmental outcome: a prospective cohort study

AIM

To describe the evolution of electroencephalogram (EEG) characteristics in infants with tuberous sclerosis complex (TSC) and the relationship with neurodevelopmental outcome at 24 months.

METHOD

Eighty-three infants were enrolled in the EPISTOP trial and underwent serial EEG follow-up until the age of 24 months (males n=45, females n=37, median age at enrolment 28d, interquartile range 14-54d). Maturation of the EEG background and epileptiform discharges were compared between the TSC1 and TSC2 variants and between preventive and conventional groups respectively.

RESULTS

Children with TSC2 more frequently had a slower posterior dominant rhythm (PDR) at 24 months (51% vs 11%, p=0.002), a higher number of epileptiform foci (median=8 vs 4, p=0.003), and a lower fraction of EEGs without epileptiform discharges (18% vs 61%, p=0.001) at follow-up. A slower PDR at 24 months was significantly associated with lower cognitive (median=70 vs 80, p=0.028) and motor developmental quotients (median=70 vs 79, p=0.008). A higher fraction of EEGs without epileptiform discharges was associated with a lower probability of autism spectrum disorder symptoms (odds ratio=0.092, 95% confidence interval=0.009-0.912, p=0.042) and higher cognitive (p=0.004), language (p=0.002), and motor (p=0.001) developmental quotients at 24 months.

INTERPRETATION

TSC2 is associated with more abnormal EEG characteristics compared to TSC1, which are predictive for neurodevelopmental outcome.

Association of Early MRI Characteristics With Subsequent Epilepsy and Neurodevelopmental Outcomes in Children With Tuberous Sclerosis Complex

BACKGROUND AND OBJECTIVE

Multiple factors have been found to contribute to the high risk of epilepsy in infants with Tuberous Sclerosis Complex (TSC), including evolution of EEG abnormalities, TSC gene mutation and MRI characteristics. The aim of the present prospective multi-center study was to: 1) identify early MRI biomarkers of epilepsy in infants with TSC aged < 6 months and before seizure onset, and 2) associate these MRI biomarkers with neurodevelopmental outcomes at 2 years of age. The study was part of the EPISTOP project.

METHODS

We evaluated brain MRIs performed in infants with TSC younger than 6 months of age. We used harmonized MRI-protocols across centers and children were monitored closely with neuropsychological evaluation, and serial video EEG. MRI characteristics defined as tubers, radial migration lines, white matter abnormalities, cysts, calcifications, subependymal nodules (SEN) and subependymal giant cell astrocytoma (SEGA) were visually evaluated and lesions were detected semi-automatically. Lesion to brain volume ratios were calculated and associated with epilepsy and neurodevelopmental outcomes at two years.

RESULTS

Lesions were assessed on MRIs from 77 TSC infants, 62 MRIs were sufficient for volume analysis. The presence of tubers and higher tuber-brain ratios were associated with the development of clinical seizures, independently of TSC gene mutation and preventive treatment. Furthermore, higher tuber-brain ratios were associated with lower cognitive and motor development quotients at two years, independently of TSC gene mutation and presence of epilepsy.

DISCUSSION

In infants with TSC, there is a significant association between characteristic TSC lesions detected on early brain MRI and development of clinical seizures, as well as neurodevelopmental outcomes in the first two years of life. According to our results, early brain MRI findings may guide clinical care for young children with TSC.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that in infants with TSC, there is a significant association between characteristic TSC lesions on early brain MRI and the development of clinical seizures and neurodevelopmental outcomes in the first two years of life.

Racial differences in the dermatological manifestations of tuberous sclerosis complex and the potential effects on diagnosis and care

Background

Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous disorder of non-malignant tumor growths throughout major organ systems and neurological, neuropsychiatric, renal, and pulmonary co-morbidities. Skin manifestations are readily visible, often develop early in life, and are major features that contribute to TSC diagnosis. Medical photographs of such manifestations are commonly shown as examples from White individuals creating a potential barrier to accurately identifying these features in darker skinned individuals.

Objectives

The aim of this report is to raise awareness of dermatological manifestations associated with TSC, compare their appearance by race, and consider how recognition of these features could impact diagnosis and treatment of TSC.

Design and Methods

We conducted a retrospective chart review at the TSC Center of Excellence (TSCOE) at the Kennedy Krieger Institute, which included all patients in the center from 2009 (inception) through the end of the calendar year 2015 and analyzed data from the TSC Alliance Natural History Database (NHD).

Results

Among TSCOE patients, 50% of Black patients were diagnosed before the age of 1 year, compared with 70% of White patients. NHD data corroborated this trend showing a significant difference with only 38% of Blacks as compared with 50% of Whites were diagnosed at age ⩽1 year. A significant difference was observed where White participants had higher odds of having received genetic testing in both data sets. While no differences in the total number of TSC features was observed in either data set, shagreen patches and cephalic fibrous plaques were more frequently recorded in the NHD for Black individuals.

Conclusion

We highlight a disparity in the representation of Black participants within the NHD, TSCOE, and TSC trials, in addition to differences in utilization of molecular testing and topical mechanistic target of rapamycin (mTOR) inhibitor therapy between Black and White individuals. We show a trend toward later diagnosis age in Black individuals. These differences between races warrant further study across additional clinical sites and other minority groups.

Profile of Autism Spectrum Disorder in Tuberous Sclerosis Complex: Results from a Longitudinal, Prospective, Multisite Study

OBJECTIVE

Tuberous sclerosis complex (TSC) is highly associated with autism spectrum disorder (ASD). Objectives of the study were to characterize autistic features in young children with TSC.

METHODS

Participants included 138 children followed from ages 3 to 36 months with TSC from the Tuberous Sclerosis Complex Autism Center of Excellence Research Network (TACERN), a multicenter, prospective observational study aimed at understanding the underlying mechanisms of ASD in TSC. Developmental and autism-specific assessments were administered, and a clinical diagnosis of ASD was determined for all participants at 36 months. Further analyses were performed on 117 participants with valid autism assessments based on nonverbal mental age greater than 15 months.

RESULTS

Prevalence of clinical diagnosis of ASD at 36 months was 25%. Nearly all autistic behaviors on the Autism Diagnostic Observation Schedule-2 (ADOS-2) and Autism Diagnostic Interview-Revised (ADI-R) were more prevalent in children diagnosed with ASD; however, autism-specific behaviors were also observed in children without ASD. Overall quality of social overtures, facial expressions, and abnormal repetitive interests and behaviors were characteristics most likely to distinguish children with ASD from those without an ASD diagnosis. Participants meeting ADOS-2 criteria but not a clinical ASD diagnosis exhibited intermediate developmental and ADOS-2 scores compared to individuals with and without ASD.

INTERPRETATION

ASD is highly prevalent in TSC, and many additional individuals with TSC exhibit a broad range of subthreshold autistic behaviors. Our findings reveal a broader autism phenotype that can be identified in young children with TSC, which provides opportunity for early targeted treatments. ANN NEUROL 2021.

Impaired myelin production due to an intrinsic failure of oligodendrocytes in mTORpathies

AIMS

We aim to evaluate if the myelin pathology observed in epilepsy-associated focal cortical dysplasia type 2B (FCD2B) and-histologically indistinguishable-cortical tubers of tuberous sclerosis complex (TSC) is primarily related to the underlying malformation or constitutes a secondary phenomenon due to the toxic microenvironment created by epileptic seizures. We also aim to investigate the possible beneficial effect of the mTOR pathway regulator everolimus on white matter pathology.

METHODS

Primary mixed glial cell cultures derived from epilepsy surgery specimens of one TSC and seven FCD2B patients were grown on polycaprolactone fibre matrices and analysed using immunofluorescence and electron microscopy. Unaffected white matter from three age-matched epilepsy patients with mild malformations of cortical development (mMCD) and one with FCD3D served as controls. Additionally, TSC2 knock-out was performed using an oligodendroglial cell line. Myelination capacities of nanofibre grown cells in an inflammatory environment after mTOR-inhibitor treatment with everolimus were further investigated.

RESULTS

Reduced oligodendroglial turnover, directly related to a lower myelin content was found in the patients' primary cells. In our culture model of myelination dynamics, primary cells grown under 'inflammatory condition' showed decreased myelination, that was repaired by treatment with everolimus.

CONCLUSIONS

Results obtained in patient-derived primary oligodendroglial and TSC2 knock-out cells suggest that maturation of oligodendroglia and production of a proper myelin sheath seem to be impaired as a result of mTOR pathway disturbance. Hence, oligodendroglial pathology may reflect a more direct effect of the abnormal genetic programme rather than to be an inactive bystander of chronic epilepsy.

Historical Patterns of Diagnosis, Treatments, and Outcome of Epilepsy Associated With Tuberous Sclerosis Complex: Results From TOSCA Registry

Background: Epilepsy is the most common neurological manifestation in individuals with tuberous sclerosis complex (TSC). However, real-world evidence on diagnosis and treatment patterns is limited. Here, we present data from TuberOus Sclerosis registry to increase disease Awareness (TOSCA) on changes in patterns of epilepsy diagnosis, treatments, and outcomes over time, and detailed epilepsy characteristics from the epilepsy substudy.

Methods: TuberOus Sclerosis registry to increase disease Awareness (TOSCA) was a multicentre, international disease registry, consisting of a main study that collected data on overall diagnostic characteristics and associated clinical features, and six substudies focusing on specific TSC manifestations. The epilepsy substudy investigated detailed epilepsy characteristics and their correlation to genotype and intelligence quotient (IQ).

Results: Epilepsy was reported in 85% of participants, more commonly in younger individuals (67.8% in 1970s to 91.8% in last decade), while rate of treatments was similar across ages (>93% for both infantile spasms and focal seizures, except prior to 1960). Vigabatrin (VGB) was the most commonly used antiepileptic drugs (AEDs). Individuals with infantile spasms showed a higher treatment response over time with lower usage of steroids. Individuals with focal seizures reported similar rates of drug resistance (32.5–43.3%). Use of vagus nerve stimulation (VNS), ketogenic diet, and surgery remained low.

Discussion: The epilepsy substudy included 162 individuals from nine countries. At epilepsy onset, most individuals with infantile spasms (73.2%) and focal seizures (74.5%) received monotherapies. Vigabatrin was first-line treatment in 45% of individuals with infantile spasms. Changes in initial AEDs were commonly reported due to inadequate efficacy. TSC1 mutations were associated with less severe epilepsy phenotypes and more individuals with normal IQ. In individuals with TSC diagnosis before seizure onset, electroencephalogram (EEG) was performed prior to seizures in only 12.5 and 25% of subsequent infantile spasms and focal seizures, respectively.

Conclusions: Our study confirms the high prevalence of epilepsy in TSC individuals and less severe phenotypes with TSC1 mutations. Vigabatrin improved the outcome of infantile spasms and should be used as first-line treatment. There is, however, still a need for improving therapies in focal seizures. Electroencephalogram follow-up prior to seizure-onset should be promoted for all infants with TSC in order to facilitate preventive or early treatment.

Effects of Mutations in TSC Genes on Neurodevelopment and Synaptic Transmission

Mutations in TSC1 or TSC2 genes are linked to alterations in neuronal function which ultimately lead to the development of a complex neurological phenotype. Here we review current research on the effects that reduction in TSC1 or TSC2 can produce on the developing neural network. A crucial feature of the disease pathophysiology appears to be an early deviation from typical neurodevelopment, in the form of structural abnormalities. Epileptic seizures are one of the primary early manifestation of the disease in the CNS, followed by intellectual deficits and autism spectrum disorders (ASD). Research using mouse models suggests that morphological brain alterations might arise from the interaction of different cellular types, and hyperexcitability in the early postnatal period might be transient. Moreover, the increased excitation-to-inhibition ratio might represent a transient compensatory adjustment to stabilize the developing network rather than a primary factor for the development of ASD symptoms. The inhomogeneous results suggest region-specificity as well as an evolving picture of functional alterations along development. Furthermore, ASD symptoms and epilepsy might originate from different but potentially overlapping mechanisms, which can explain recent observations obtained in patients. Potential treatment is determined not only by the type of medicament, but also by the time point of treatment.

Natural History Studies and Clinical Trial Readiness for Genetic Developmental and Epileptic Encephalopathies

The developmental and epileptic encephalopathies (DEEs) are the most severe group of epilepsies. They usually begin in infancy or childhood with drug-resistant seizures, epileptiform EEG patterns, developmental slowing or regression, and cognitive impairment. DEEs have a high mortality and profound morbidity; comorbidities are common including autism spectrum disorders. With advances in genetic sequencing, over 400 genes have been implicated in DEEs, with a genetic cause now identified in over 50% patients. Each genetic DEE typically has a broad genotypic-phenotypic spectrum, based on the underlying pathophysiology. There is a pressing need to improve health outcomes by developing novel targeted therapies for specific genetic DEE phenotypes that not only improve seizure control, but also developmental outcomes and comorbidities. Clinical trial readiness relies firstly on a deep understanding of phenotype-genotype correlation and evolution of a condition over time, in order to select appropriate patients for clinical trials. Understanding the natural history of the disorder informs assessment of treatment efficacy in terms of both clinical outcome and biomarker utility. Natural history studies (NHS) provide a high quality, integrated, comprehensive approach to understanding a complex disease and underpin clinical trial design for novel therapies. NHS are pre-planned observational studies designed to track the course of a disease and identify demographic, genetic, environmental, and other variables, including biomarkers, that correlate with the disease's evolution and outcomes. Due to the rarity of individual genetic DEEs, appropriately funded high-quality DEE NHS will be required, with sustainable frameworks and equitable access to affected individuals globally.

Factors associated with autism spectrum disorder in children with tuberous sclerosis complex: a systematic review and meta-analysis

AIM

To investigate associations between clinical factors and the development of autism spectrum disorder (ASD) in children with tuberous sclerosis complex (TSC), specifically seizures, electroencephalogram abnormalities, tubers and other neurostructural abnormalities, and genetic factors.

METHOD

MEDLINE, Embase, PubMed, the Cochrane Library, and Web of Science were searched until January 2019. Studies that considered the predefined factors for development of ASD in children with TSC were included, following PRISMA-P guidelines. Two authors independently reviewed titles, abstracts, and full texts, extracted data, and assessed risk of bias.

RESULTS

Forty-two studies with 3542 children with TSC were included. ASD was associated with a history of seizures (odds ratio [OR] 3.79, 95% confidence interval [CI] 1.77-8.14), infantile spasms compared with other seizure types (OR 3.04, 95% CI 2.17-4.27), onset of any seizure type during infancy (OR 2.65, 95% CI 1.08-6.54), and male sex (OR 1.62, 95% CI 1.23-2.14). There was no association with tuber number, tuber location, or genotype.

INTERPRETATION

While a causal link between seizures and ASD in children with TSC cannot be inferred, a strong association between seizures and ASD in children with TSC, particularly with seizure onset during infancy and specifically infantile spasms, is present. Children with TSC and infant-onset seizures should be monitored for emerging features of ASD. What this paper adds Seizures and autism spectrum disorder (ASD) strongly associate in children with tuberous sclerosis complex (TSC). Infant-onset seizures and infantile spasms are particularly strongly associated with ASD in TSC.

Developmental and epileptic encephalopathies: what we do and do not know

Developmental encephalopathies, including intellectual disability and autistic spectrum disorder, are frequently associated with infant epilepsy. Epileptic encephalopathy is used to describe an assumed causal relationship between epilepsy and developmental delay. Developmental encephalopathies pathogenesis more independent from epilepsy is supported by the identification of several gene variants associated with both developmental encephalopathies and epilepsy, the possibility for gene-associated developmental encephalopathies without epilepsy, and the continued development of developmental encephalopathies even when seizures are controlled. Hence, 'developmental and epileptic encephalopathy' may be a more appropriate term than epileptic encephalopathy. This update considers the best studied 'developmental and epileptic encephalopathy' gene variants for illustrative support for 'developmental and epileptic encephalopathy' over epileptic encephalopathy. Moreover, the interaction between epilepsy and developmental encephalopathies is considered with respect to influence on treatment decisions. Continued research in genetic testing will increase access to clinical tests, earlier diagnosis, better application of current treatments, and potentially provide new molecular-investigated treatments.

mTOR inhibitor improves autistic-like behaviors related to Tsc2 haploinsufficiency but not following developmental status epilepticus

Background

Tuberous sclerosis complex (TSC), a multi-system genetic disorder often associated with autism spectrum disorder (ASD), is caused by mutations of TSC1 or TSC2, which lead to constitutive overactivation of mammalian target of rapamycin (mTOR). In several Tsc1+/- and Tsc2+/- animal models, cognitive and social behavior deficits were reversed by mTOR inhibitors. However, phase II studies have not shown amelioration of ASD and cognitive deficits in individuals with TSC during mTOR inhibitor therapy. We asked here if developmental epilepsy, common in the majority of individuals with TSC but absent in most animal models, could explain the discrepancy.

Methods

At postnatal day P12, developmental status epilepticus (DSE) was induced in male Tsc2+/- (Eker) and wild-type rats, establishing four experimental groups including controls. In adult animals (n = 36), the behavior was assessed in the paradigms of social interaction test, elevated plus-maze, light-dark test, Y-maze, and novel object recognition. The testing was carried out before medication (T1), during a 2-week treatment with the mTOR inhibitor everolimus (T2) and after an 8-week washing-out (T3). Electroencephalographic (EEG) activity was recorded in a separate set of animals (n = 18).

Results

Both Tsc2+/- mutation and DSE caused social behavior deficits and epileptiform EEG abnormalities (T1). Everolimus led to a persistent improvement of the social deficit induced by Tsc2+/-, while deficits related to DSE did not respond to everolimus (T2, T3).

Conclusions

These findings may contribute to an explanation why ASD symptoms in individuals with TSC, where comorbid early-onset epilepsy is common, were not reliably ameliorated by mTOR inhibitors in clinical studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-021-09357-2.

Early epileptiform EEG activity in infants with tuberous sclerosis complex predicts epilepsy and neurodevelopmental outcomes

OBJECTIVE

To study the association between timing and characteristics of the first electroencephalography (EEG) with epileptiform discharges (ED-EEG) and epilepsy and neurodevelopment at 24 months in infants with tuberous sclerosis complex (TSC).

METHODS

Patients enrolled in the prospective Epileptogenesis in a genetic model of epilepsy - Tuberous sclerosis complex (EPISTOP) trial, had serial EEG monitoring until the age of 24 months. The timing and characteristics of the first ED-EEG were studied in relation to clinical outcome. Epilepsy-related outcomes were analyzed separately in a conventionally followed group (initiation of vigabatrin after seizure onset) and a preventive group (initiation of vigabatrin before seizures, but after appearance of interictal epileptiform discharges [IEDs]).

RESULTS

Eighty-three infants with TSC were enrolled at a median age of 28 days (interquartile range [IQR] 14-54). Seventy-nine of 83 patients (95%) developed epileptiform discharges at a median age of 77 days (IQR 23-111). Patients with a pathogenic TSC2 variant were significantly younger (P-value .009) at first ED-EEG and more frequently had multifocal IED (P-value .042) than patients with a pathogenic TSC1 variant. A younger age at first ED-EEG was significantly associated with lower cognitive (P-value .010), language (P-value .001), and motor (P-value .013) developmental quotients at 24 months. In the conventional group, 48 of 60 developed seizures. In this group, the presence of focal slowing on the first ED-EEG was predictive of earlier seizure onset (P-value .030). Earlier recording of epileptiform discharges (P-value .019), especially when multifocal (P-value .026) was associated with higher risk of drug-resistant epilepsy. In the preventive group, timing, distribution of IED, or focal slowing, was not associated with the epilepsy outcomes. However, when multifocal IEDs were present on the first ED-EEG, preventive treatment delayed the onset of seizures significantly (P-value <.001).

SIGNIFICANCE

Early EEG findings help to identify TSC infants at risk of severe epilepsy and neurodevelopmental delay and those who may benefit from preventive treatment with vigabatrin.

Myelin Pathology Beyond White Matter in Tuberous Sclerosis Complex (TSC) Cortical Tubers

Tuberous sclerosis complex (TSC) is a monogenetic disease that arises due to mutations in either the TSC1 or TSC2 gene and affects multiple organ systems. One of the hallmark manifestations of TSC are cortical malformations referred to as cortical tubers. These tubers are frequently associated with treatment-resistant epilepsy. Some of these patients are candidates for epilepsy surgery. White matter abnormalities, such as loss of myelin and oligodendroglia, have been described in a small subset of resected tubers but mechanisms underlying this phenomenon are unclear. Herein, we analyzed a variety of neuropathologic and immunohistochemical features in gray and white matter areas of resected cortical tubers from 46 TSC patients using semi-automated quantitative image analysis. We observed divergent amounts of myelin basic protein as well as numbers of oligodendroglia in both gray and white matter when compared with matched controls. Analyses of clinical data indicated that reduced numbers of oligodendroglia were associated with lower numbers on the intelligence quotient scale and that lower amounts of myelin-associated oligodendrocyte basic protein were associated with the presence of autism-spectrum disorder. In conclusion, myelin pathology in cortical tubers extends beyond the white matter and may be linked to cognitive dysfunction in TSC patients.

Prevention of Epilepsy in Infants with Tuberous Sclerosis Complex in the EPISTOP Trial

OBJECTIVE

Epilepsy develops in 70 to 90% of children with tuberous sclerosis complex (TSC) and is often resistant to medication. Recently, the concept of preventive antiepileptic treatment to modify the natural history of epilepsy has been proposed. EPISTOP was a clinical trial designed to compare preventive versus conventional antiepileptic treatment in TSC infants.

METHODS

In this multicenter study, 94 infants with TSC without seizure history were followed with monthly video electroencephalography (EEG), and received vigabatrin either as conventional antiepileptic treatment, started after the first electrographic or clinical seizure, or preventively when epileptiform EEG activity before seizures was detected. At 6 sites, subjects were randomly allocated to treatment in a 1:1 ratio in a randomized controlled trial (RCT). At 4 sites, treatment allocation was fixed; this was denoted an open-label trial (OLT). Subjects were followed until 2 years of age. The primary endpoint was the time to first clinical seizure.

RESULTS

In 54 subjects, epileptiform EEG abnormalities were identified before seizures. Twenty-seven were included in the RCT and 27 in the OLT. The time to the first clinical seizure was significantly longer with preventive than conventional treatment [RCT: 364 days (95% confidence interval [CI] = 223-535) vs 124 days (95% CI = 33-149); OLT: 426 days (95% CI = 258-628) vs 106 days (95% CI = 11-149)]. At 24 months, our pooled analysis showed preventive treatment reduced the risk of clinical seizures (odds ratio [OR] = 0.21, p = 0.032), drug-resistant epilepsy (OR = 0.23, p = 0.022), and infantile spasms (OR = 0, p < 0.001). No adverse events related to preventive treatment were noted.

INTERPRETATION

Preventive treatment with vigabatrin was safe and modified the natural history of seizures in TSC, reducing the risk and severity of epilepsy. ANN NEUROL 2021;89:304-314.

HFO to Measure Seizure Propensity and Improve Prognostication in Patients With Epilepsy

The study of high frequency oscillations (HFO) in the electroencephalogram (EEG) as biomarkers of epileptic activity has merely focused on their spatial location and relationship to the epileptogenic zone. It has been suggested in several ways that the amount of HFO at a certain point in time may reflect the disease activity or severity. This could be clinically useful in several ways, especially as noninvasive recording of HFO appears feasible. We grouped the potential hypotheses into 4 categories: (1) HFO as biomarkers to predict the development of epilepsy; (2) HFO as biomarkers to predict the occurrence of seizures; (3) HFO as biomarkers linked to the severity of epilepsy, and (4) HFO as biomarkers to evaluate outcome of treatment. We will review the literature that addresses these 4 hypotheses and see to what extent HFO can be used to measure seizure propensity and help determine prognosis of this unpredictable disease.

Prediction of Neurodevelopment in Infants With Tuberous Sclerosis Complex Using Early EEG Characteristics

Tuberous Sclerosis Complex (TSC) is a multisystem genetic disorder with a high risk of early-onset epilepsy and a high prevalence of neurodevelopmental comorbidities, including intellectual disability and autism spectrum disorder (ASD). Therefore, TSC is an interesting disease model to investigate early biomarkers of neurodevelopmental comorbidities when interventions are favourable. We investigated whether early EEG characteristics can be used to predict neurodevelopment in infants with TSC. The first recorded EEG of 64 infants with TSC, enrolled in the international prospective EPISTOP trial (recorded at a median gestational age 42 4/7 weeks) was first visually assessed. EEG characteristics were correlated with ASD risk based on the ADOS-2 score, and cognitive, language, and motor developmental quotients (Bayley Scales of Infant and Toddler Development III) at the age of 24 months. Quantitative EEG analysis was used to validate the relationship between EEG background abnormalities and ASD risk. An abnormal first EEG (OR = 4.1, p-value = 0.027) and more specifically a dysmature EEG background (OR = 4.6, p-value = 0.017) was associated with a higher probability of ASD traits at the age of 24 months. This association between an early abnormal EEG and ASD risk remained significant in a multivariable model, adjusting for mutation and treatment (adjusted OR = 4.2, p-value = 0.029). A dysmature EEG background was also associated with lower cognitive (p-value = 0.029), language (p-value = 0.001), and motor (p-value = 0.017) developmental quotients at the age of 24 months. Our findings suggest that early EEG characteristics in newborns and infants with TSC can be used to predict neurodevelopmental comorbidities.

Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis

Tuberous sclerosis complex (TSC) represents the prototypic monogenic disorder of the mammalian target of rapamycin (mTOR) pathway dysregulation. It provides the rational mechanistic basis of a direct link between gene mutation and brain pathology (structural and functional abnormalities) associated with a complex clinical phenotype including epilepsy, autism, and intellectual disability. So far, research conducted in TSC has been largely neuron-oriented. However, the neuropathological hallmarks of TSC and other malformations of cortical development also include major morphological and functional changes in glial cells involving astrocytes, oligodendrocytes, NG2 glia, and microglia. These cells and their interglial crosstalk may offer new insights into the common neurobiological mechanisms underlying epilepsy and the complex cognitive and behavioral comorbidities that are characteristic of the spectrum of mTOR-associated neurodevelopmental disorders. This review will focus on the role of glial dysfunction, the interaction between glia related to mTOR hyperactivity, and its contribution to epileptogenesis in TSC. Moreover, we will discuss how understanding glial abnormalities in TSC might give valuable insight into the pathophysiological mechanisms that could help to develop novel therapeutic approaches for TSC or other pathologies characterized by glial dysfunction and acquired mTOR hyperactivation.

Autism and Epilepsy in Patients With Tuberous Sclerosis Complex

Introduction: Individuals with Tuberous Sclerosis Complex (TSC) are at increased risk of developing both epilepsy and autism spectrum disorder (ASD), but the relationship between these conditions is little understood. We reviewed published reports to elucidate the relationship between ASD, epilepsy, and TSC, and to define the genetic and neurological risk factors. Methods: Articles (January 2004-May 2019) were identified via PubMed, EMBASE, and CENTRAL databases. Article inclusion required report on individuals with TSC-associated ASD and epilepsy with prevalence, odds ratio, or rate report on the comorbidity of ASD in epileptic patients due to TSC. Results: A total of 841 abstracts were identified in the original search. Thirty-six articles were included, which identified study populations, ASD measures used, and study confounders as bias factors. This review included 2,666 TSC patients, with a mean age of 15.9 years (range 1.94-30.3 years). The percentage of TSC patients with epilepsy and autism was 33.7%. Patients with TSC and autism showed more frequent seizures and earlier epilepsy onset than TSC patients without autism. ASD and intractable epilepsy were both predicted by a higher number of areas with dysplastic features revealed in brain MR scans. ASD, the onset of seizures in children <2 years of age, and >3 tubers have all been associated with an increased risk of refractory epilepsy in TSC patients. However, the direction of the relationship is not clear because a history of epilepsy, or infantile spasms in patients with TSC is also associated with an increased likelihood of ASD. Overall, 73.2% of patients carried TSC2 genetic variant and, among patients with TSC and autism, the percentage of TSC2 individuals was 85.6%. Conclusions: The complex interrelationship between TSC, autism, and epilepsy, coupled with limited knowledge on the neurobiological basis for the interrelationship, limits overall understanding and opportunities for management. The results of this review highlight the need for early identification and management to optimize favorable outcomes in the most vulnerable individuals with TSC. Regardless of whether studies are considered individually or collectively, interpretation is made difficult due to the differences between the studies, most notably between methods and diagnostic criteria used to assess intellectual ability.

Is autism driven by epilepsy in infants with Tuberous Sclerosis Complex?

Objective

To evaluate the relationship between age at seizure onset and neurodevelopmental outcome at age 24 months in infants with TSC, as well as the effect on neurodevelopmental outcome of early versus conventional treatment of epileptic seizures with vigabatrin (80–150 mg/kg/day).

Methods

Infants with TSC, aged ≤4 months and without previous seizures were enrolled in a prospective study and closely followed with monthly video EEG and serial standardized neurodevelopmental testing (Bayley Scales of Infant Development and Autism Diagnostic Observation Schedule).

Results

Eighty infants were enrolled. At the age of 24 months testing identified risk of Autism Spectrum Disorder (ASD) in 24/80 children (30.0%), and developmental delay (DD) in 26/80 (32.5%). Children with epilepsy (51/80; 63.8%) had a higher risk of ASD (P = 0.02) and DD (P = 0.001). Overall, no child presented with moderate or severe DD at 24 months (developmental quotient < 55). In 20% of children abnormal developmental trajectories were detected before the onset of seizures. Furthermore, 21% of all children with risk of ASD at 24 months had not developed seizures at that timepoint. There was no significant difference between early and conventional treatment with respect to rate of risk of ASD (P = 0.8) or DD (P = 0.9) at 24 months.

Interpretation

This study confirms a relationship between epilepsy and risk of ASD/DD. However, in this combined randomized/open label study, early treatment with vigabatrin did not alter the risk of ASD or DD at age 2 years.

Why we urgently need improved seizure and epilepsy therapies for children and neonates

In contrast to epilepsy in adolescents and adults, neonatal seizures and early onset epilepsy poses unique challenges with significant repercussion for treatment choices. Most importantly, high seizure burden and epileptic encephalopathy are associated with developmental, behavioural and cognitive problems. The causes are multifactorial and include etiology, seizure burden, epileptic encephalopathy, but also antiseizure medication. In contrast to adults and older children only very few drugs have been licenced for infants and neonates, and after a long delay. Very recently, extrapolation of adult data has become possible as a path to speed up drug development for younger children but this is not necessarily possible for infants and neonates. With the advances in understanding the molecular basis of many epilepsies, targeted therapies become available, for example for KCNQ2 mutation related epilepsies, Dravet syndrome or tuberous sclerosis complex. Drug trials in neonates are particularly challenging because of their inconspicuous clinical presentation, the need for continuous EEG monitoring, high co-morbidity, and poor response to antiepileptic drugs. There is an urgent need for development of new drugs, evaluation of safety and efficacy of current antiseizure drugs, as well as for national policies and guidelines for the management of seizures and epilepsy in neonates and infants. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

Scalp EEG spikes predict impending epilepsy in TSC infants: A longitudinal observational study

Objective

To determine if routine electroencephalography (EEG) in seizure‐naive infants with tuberous sclerosis complex (TSC) can predict epilepsy and subsequent neurocognitive outcomes.

Methods

Forty infants 7 months of age or younger and meeting the genetic or clinical diagnostic criteria for tuberous sclerosis were enrolled. Exclusion criteria included prior history of seizures or treatment with antiseizure medications. At each visit, seizure history and 1‐hour awake and asleep video‐EEG, standardized across all sites, were obtained until 2 years of age. Developmental assessments (Mullen and Vineland‐II) were completed at 6, 12, and 24 months of age.

Results

Of 40 infants enrolled (mean age of 82.4 days), 32 completed the study. Two were lost to follow‐up and six were treated with antiepileptic drugs (AEDs) due to electrographic seizures and/or interictal epileptiform discharges (IEDs) on their EEG studies prior to the onset of clinical seizures. Seventeen of the 32 remaining children developed epilepsy at a mean age of 7.5 months (standard deviation [SD] = 4.4). Generalized/focal slowing, hypsarrhythmia, and generalized/focal attenuation were not predictive for the development of clinical seizures. Presence of IEDs had a 77.3% positive predictive value and absence a 70% negative predictive value for developing seizures by 2 years of age. IEDs preceded clinical seizure onset by 3.6 months (mean). Developmental testing showed significant decline, only in infants with ongoing seizures, but not infants who never developed seizures or whose seizures came under control.

Significance

IEDs identify impending epilepsy in the majority (77%) of seizure‐naive infants with TSC. The use of a 1‐hour awake and asleep EEG can be used as a biomarker for ongoing epileptogenesis in most, but not all, infants with TSC. Persistent seizures, but not history of interictal epileptiform activity or history of well‐controlled seizures, correlated with low scores on the Vineland and Mullen tests at 2 years of age.