EEG features and epilepsy in patients with autism

Entropy, complexity, and spectral features of EEG signals in autism and typical development: a quantitative approach

Autism spectrum disorder (ASD) is a neurodevelopmental condition that affects the brain's function. Electroencephalography (EEG) is a non-invasive technique that measures the electrical activity of the brain and can reveal its dynamics and information processing. This study explores an eyes-opened resting state quantitative EEG analysis of 49 children with ASD and 39 typically developing (TD or Control) children, using various features of entropy and complexity. Time and frequency domain features were applied for all EEG channels, such as the power spectra, brain rate, sample entropy, permutation entropy, spectral entropy, Tsallis entropy, Rényi entropy, Lempel-Ziv complexity, and Higuchi fractal dimension. The features were compared between the ASD and TD groups and tested for statistical significance. The results showed that the ASD group had a lower brain rate, higher Tsallis entropy and Rényi entropy, and lower Lempel-Ziv complexity than the TD group. The entropy results show impaired neural synchronization, increased randomness, and noise in ASD. The Lempel-Ziv complexity results showed that it is a potential indicator of the existence of focal spikes in the EEG signals of ASD. The brain-rate results show a low level of arousal in ASD. The findings suggest that entropy and complexity measures can be useful tools for characterizing the EEG features of ASD and provide insights into the neurophysiological mechanisms of the disorder.

EEG findings and clinical severity and quality of life in non-epileptic patients with autism spectrum disorders

Electroencephalogram (EEG) abnormalities could be seen in up to 60% of non-epileptic children with autism spectrum disorder (ASD). They have been used as biomarkers of ASD severity. The objective of our study is to identify EEG abnormalities in children with different degrees of ASD severity based on the Autism Treatment Evaluation Checklist (ATEC). We also want to assess the quality of life for children with ASD. All of the children underwent at least one hour of sleep-deprived EEG. Forty-five children were enrolled, of whom 42 were male. EEG abnormalities were found in 10 (22.2%) children, predominantly in the bilateral frontal areas. There were no differences in EEG findings among the mild, moderate, and severe ASD groups. The severity of ASD was associated with female sex (p-value = 0.013), ASD with attention deficit hyperactivity disorder (ADHD) (p-value = 0.032), ASD children taking medications (p-value = 0.048), and a lower Pediatric Quality of Life Inventory (PedsQL) (p-value <0.001). Social and emotional domains were the most problematic for health-related quality of life in ASD children, according to parent reports of PedsQL. Further studies with a larger sample size will help to clarify the potential associations between EEG abnormalities and the severity of ASD, as well as the impact on quality of life.

A machine learning model based on CHAT-23 for early screening of autism in Chinese children

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental condition that significantly impacts the mental, emotional, and social development of children. Early screening for ASD typically involves the use of a series of questionnaires. With answers to these questionnaires, healthcare professionals can identify whether a child is at risk for developing ASD and refer them for further evaluation and diagnosis. CHAT-23 is an effective and widely used screening test in China for the early screening of ASD, which contains 23 different kinds of questions.

Methods

We have collected clinical data from Wuxi, China. All the questions of CHAT-23 are regarded as different kinds of features for building machine learning models. We introduce machine learning methods into ASD screening, using the Max-Relevance and Min-Redundancy (mRMR) feature selection method to analyze the most important questions among all 23 from the collected CHAT-23 questionnaires. Seven mainstream supervised machine learning models were built and experiments were conducted.

Results

Among the seven supervised machine learning models evaluated, the best-performing model achieved a sensitivity of 0.909 and a specificity of 0.922 when the number of features was reduced to 9. This demonstrates the model's ability to accurately identify children for ASD with high precision, even with a more concise set of features.

Discussion

Our study focuses on the health of Chinese children, introducing machine learning methods to provide more accurate and effective early screening tests for autism. This approach not only enhances the early detection of ASD but also helps in refining the CHAT-23 questionnaire by identifying the most relevant questions for the diagnosis process.

Autism and Epilepsy

Epilepsy is one of the most common comorbidities in individuals with autism spectrum disorders (ASDs). Risk factors include the presence of developmental delay/intellectual disability, female sex, age, and an underlying genetic condition. Due to higher prevalence of epilepsy in ASD, it is important to have a high index of suspicion for seizures and refer to a neurologist if there are concerns. Genetic testing is recommended for all children with ASD but it becomes more high yield in children with epilepsy and ASD.

Children with Autism Spectrum Disorder and Abnormalities of Clinical EEG: A Qualitative Review

Over the last decade, the comorbidity between Autism Spectrum Disorder (ASD) and epilepsy has been widely demonstrated, and many hypotheses regarding the common neurobiological bases of these disorders have been put forward. A variable, but significant, prevalence of abnormalities on electroencephalogram (EEG) has been documented in non-epileptic children with ASD; therefore, several scientific studies have recently tried to demonstrate the role of these abnormalities as a possible biomarker of altered neural connectivity in ASD individuals. This narrative review intends to summarize the main findings of the recent scientific literature regarding abnormalities detected with standard EEG in children/adolescents with idiopathic ASD. Research using three different databases (PubMed, Scopus and Google Scholar) was conducted, resulting in the selection of 10 original articles. Despite an important lack of studies on preschoolers and a deep heterogeneity in results, some authors speculated on a possible association between EEG abnormalities and ASD characteristics, in particular, the severity of symptoms. Although this correlation needs to be more strongly elucidated, these findings may encourage future studies aimed at demonstrating the role of electrical brain abnormalities as an early biomarker of neural circuit alterations in ASD, highlighting the potential diagnostic, prognostic and therapeutic value of EEG in this field.

Self-limited childhood epilepsies are disorders of the perisylvian communication system, carrying the risk of progress to epileptic encephalopathies-Critical review

"Sleep plasticity is a double-edged sword: a powerful machinery of neural build-up, with a risk to epileptic derailment." We aimed to review the types of self-limited focal epilepsies..."i.e. keep as two separate paragraphs" We aimed to review the types of self-limited focal epilepsies: (1) self-limited focal childhood epilepsy with centrotemporal spikes, (2) atypical Rolandic epilepsy, and (3) electrical status epilepticus in sleep with mental consequences, including Landau-Kleffner-type acquired aphasia, showing their spectral relationship and discussing the debated topics. Our endeavor is to support the system epilepsy concept in this group of epilepsies, using them as models for epileptogenesis in general. The spectral continuity of the involved conditions is evidenced by several features: language impairment, the overarching presence of centrotemporal spikes and ripples (with changing electromorphology across the spectrum), the essential timely and spatial independence of interictal epileptic discharges from seizures, NREM sleep relatedness, and the existence of the intermediate-severity "atypical" forms. These epilepsies might be the consequences of a genetically determined transitory developmental failure, reflected by widespread neuropsychological symptoms originating from the perisylvian network that have distinct time and space relations from secondary epilepsy itself. The involved epilepsies carry the risk of progression to severe, potentially irreversible encephalopathic forms.

Clinical features and drug-resistance in pediatric epilepsy with co-occurring autism: A retrospective comparative cohort study

OBJECTIVE

We conducted a retrospective comparative cohort study to determine the phenotypic and real-world management differences in children with epilepsy and co-occurring autism as compared to those without autism.

METHODS

Clinical variables, EEG, brain MRI, genetic results, medical and non-medical treatment were compared between 156 children with both epilepsy and autism, 156 randomly selected and 156 demographically matched children with epilepsy only. Logistic regression analyses were conducted to determine predictors of drug-resistant epilepsy (DRE).

RESULTS

As compared to the'matched' cohort, more patients with autism had generalized motor seizures although not statistically significant after Benjamini-Hochberg correction (54.5%, vs 42.3%, p = .0314); they had a lower rate of electroclinical syndromes (12.8%, vs 30.1%, p = .0002). There were more incidental MRI findings but less positive MRI findings to explain their epilepsy in children with autism (26.3%, vs 13.8% and 14.3%, vs 34.2%, respectively; p = .0003). In addition, LEV, LTG, and VPA were the most common ASMs prescribed to children with autism, as opposed to LEV, OXC, and LTG in children without autism. No difference in the major EEG abnormalities was observed. Although the rates of DRE were similar (24.8%, vs 26.6%, p = .7203), we identified two clinical and five electrographic correlates with DRE in children with both epilepsy and autism and a final prediction modeling of DRE that included EEG ictal findings, focal onset seizures, generalized motor seizures, abnormal EEG background, age of epilepsy onset, and history of SE, which were distinct from those in children without autism.

SIGNIFICANCE

Our study indicates that detailed seizure history and EEG findings are the most important evaluation and prediction tools for the development of DRE in children with epilepsy and co-occurring autism. Further studies of epilepsy in specific autism subgroups based on their etiology and clinical severity are warranted.

Staring spells in children with autism spectrum disorder: A clinical dilemma

To assess the role of clinical features in diagnosing seizures in children with autism spectrum disorder who present with staring spells. A 10-year retrospective chart analysis of autism spectrum disorder patients aged 3–14 years was performed at a tertiary care children’s hospital. Patient demographics, clinical presentation, and epileptic seizure versus non-epileptic spell diagnosis were assessed. Target episodes of staring spells were captured during a long-term electroencephalogram monitoring record. Multilevel likelihood ratios and a receiver operating characteristic curve were determined using 8 of the 11 clinical variables. Among the cohort of 140 patients with autism spectrum disorder, 16% were diagnosed with epileptic seizures with the most common seizure being atypical absence seizures (64%). Clinical semiology differed between those diagnosed with epileptic seizures versus those diagnosed with non-epileptic spells in the average duration of episodes (42 s vs 87 s), frequency of spells per week (6 vs 11.5 spells), increase in frequency of staring spells over time (100% vs 40%), and response to verbal stimulation (0% vs 100%), respectively. Multilevel likelihood ratios based on the receiver operating characteristic curves and clinical semiology features may be helpful in differentiating epileptic seizures from non-epileptic spells in children with autism spectrum disorder.

Lay Abstract

It is a common occurrence for children with autism spectrum disorder to be diagnosed with staring spells. Staring spells are defined as periods of time when children “space out” and are subcategorized as either “absence seizures” (brain activity resembling a seizure but with no physical seizure symptoms) or “non-epileptic spells” (inattentiveness or daydreaming). Due to the subtle characteristics of staring spells, they are usually diagnosed via long-term video electroencephalogram. The child is monitored for 3–5 days with an electroencephalogram which records brain waves. An electroencephalogram may be difficult to perform in children with autism spectrum disorder due to behavior, cognitive, or sensory concerns. Therefore, we wanted to investigate other clinical characteristics that may help us differentiate between epileptic seizures versus non-epileptic spells in children with autism spectrum disorder presenting with staring spells. We reviewed 140 charts retrospectively from the years of 2010–2021. We abstracted demographic and clinical information from the electronic medical record system and reviewed electroencephalogram videos to group the 140 children into epileptic seizure diagnosis group versus non-epileptic spell group. Of the 140 children in this study, 22 were diagnosed with epileptic seizures and the remaining were diagnosed with non-epileptic spells. We found that the two groups differed in certain clinical characteristics such as how long the staring spells lasted, how many staring spells the child had in 1 week, and whether they responded to verbal commands. We believe that clinical features may be helpful in differentiating epileptic seizures from non-epileptic spells in children with autism spectrum disorder.

Detection of Electroencephalographic Abnormalities and Its Associated Factors among Children with Autism Spectrum Disorder in Thailand

Epilepsy often causes more severe behavioral problems in children with autism spectrum disorder (ASD) and is strongly associated with poor cognitive functioning. Interestingly, individuals with ASD without a history of epilepsy can have abnormal electroencephalographic (EEG) activity. The aim of this study was to examine associations between EEG abnormalities and the ASD severity in children. The children with ASD who enrolled at the Rajanagarindra Institute of Child Development, Thailand were included in this study. The severity of ASD was measured by interviewing their parents with the Thai autism treatment evaluation checklist. The short sensory profile checklist was used for screening the abnormality of children in each domain. Ordinal logistic regression analysis was used to examine associations between factors potentially linked to EEG abnormalities. Most of the study participants were boys (87.5%) and the median age was 5 years. Among the 128 children, 69.5% showed EEG abnormalities (41.4% slow-wave and 28.1% epileptiform-discharge). The results show that a larger number of symptoms and increased severity of ASD were independently associated with a higher risk of EEG abnormalities. Our results emphasize the need for guidelines on the presence of EEG abnormalities in children with ASD for the early detection of epilepsy and improving treatment outcomes.

Epilepsy and EEG Abnormalities in Children with Autism Spectrum Disorders

OBJECTIVE

To evaluate the prevalence of epilepsy and  electroencephalographic abnormalities in children with autism spectrum disorders (ASD) and determine their risk factors.

METHODS

This cross-sectional study was conducted over one year in children with ASD aged between 3 and 14 y. Classification of epilepsy and routine electroencephalography (EEG) recordings were done for all the patients. Developmental and cognitive assessments were done using Developmental Profile 3. Children were divided into three groups: ASD with epilepsy, ASD with isolated electroencephalographic abnormalities, and ASD with neither epilepsy nor electroencephalographic abnormalities.

RESULTS

One hundred children with ASD were enrolled. Epilepsy was reported in 23% and subclinical electroencephalographic abnormalities were documented in 8%. The most common seizure types were generalized-onset tonic-clonic (48%), focal-onset with impaired awareness (17%), and focal to bilateral tonic-clonic seizures (17%). In children with subclinical epileptiform discharges, focal abnormalities were most common (75%) and were maximally seen over the temporal region (50%). Subnormal intellect (88.6%) and abnormal global developmental score (82%) were noted in the majority of children. Female gender, abnormal neurological examination, and adverse perinatal events were significantly associated with epilepsy. Of these, female gender and adverse perinatal events were independent predictors of epilepsy. Isolated EEG abnormalities were significantly associated with abnormal neurological examination in comparison with autistic children without epilepsy/EEG abnormalities.

CONCLUSION

Epilepsy is seen in up to one-fourth children with ASD. Female gender and adverse perinatal events are independent risk factors for epilepsy. Subclinical or isolated EEG abnormalities are associated with abnormal neurological examination.

Knowledge Atlas of the Co-Occurrence of Epilepsy and Autism: A Bibliometric Analysis and Visualization Using VOSviewer and CiteSpace

OBJECTIVE

This study aimed to analyze research on epilepsy in autism and autism in epilepsy using VOSviewer and CiteSpace to identify research hotspots and future directions.

METHODS

We searched the Web of Science Core Collection (WoSCC) for relevant studies about epilepsy in autism and autism in epilepsy published from inception to 31 May 2022. VOSviewer and CiteSpace were used to analyze the authors, institutions, countries, publishing journals, reference co-citation patterns, keyword co-occurrence, keyword clustering, keywords with citation bursts, and other aspects to construct a knowledge atlas.

RESULTS

A total of 473 publications related to epilepsy/autism were retrieved. The number of publications about epilepsy/ASD has generally increased over time, with some fluctuations. The USA (202 papers) and University of California-Los Angeles (15 papers) were the leading country and institution, respectively, in this field. Frye, Richard E. was the most published author (9 papers). Notably, collaboration between institutions, countries, and authors does not appear to be active. Hot topics and research frontiers include intellectual disability and exploring the mechanism of epilepsy/ASD from a genetics perspective.

CONCLUSION

This analysis identified the most influential publications, authors, journals, institutions, and countries in the field of epilepsy/ASD research. Using co-occurrence and evolution analyses, the status of the field was identified and future trends were predicted.

Electroencephalogram Abnormalities and Epilepsy in Autism Spectrum Disorders: Clinical and Electroencephalogram Findings

It has been known for several decades that epilepsy and autism spectrum disorders (ASD) are related to each other. Epilepsy frequently accompanies ASD. The purpose of this study was to investigate relationship between clinical and electroencephalogram (EEG) findings in ASD patients and to identify EEG characteristics that may create a disposition to epilepsy in ASD by examining differences in clinical and EEG findings between patients diagnosed with ASD without epilepsy and ASD with epilepsy. A total of 102 patients aged 2 to 18 years and diagnosed with ASD based on Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) diagnostic criteria between January 2017 and June 2019 were included in the study. Patients were assigned into two groups: (1) ASD with epilepsy and (2) ASD without epilepsy. Clinical findings were retrieved from patients' files, and EEG findings from first EEG records in the EEG laboratory at the time of diagnosis. EEG findings were defined as central, parietal, frontal, temporal, or generalized, depending on the location of rhythmic discharges. The incidence of epilepsy in our ASD patients was 33.7% and that of febrile convulsion was 4%. Generalized motor seizures were the most common seizure type. Epileptic discharges most commonly derived from the central and frontal regions. These abnormalities, especially frontal and central rhythmic discharges, may represent a precursor for the development of epilepsy in ASD patients.

Epileptiform discharges relate to altered functional brain networks in autism spectrum disorders

Many individuals with autism spectrum disorders have comorbid epilepsy. Even in the absence of observable seizures, interictal epileptiform discharges are common in individuals with autism spectrum disorders. However, how these interictal epileptiform discharges are related to autistic symptomatology remains unclear. This study used magnetoencephalography to investigate the relation between interictal epileptiform discharges and altered functional brain networks in children with autism spectrum disorders. Instead of particularly addressing individual brain regions, we specifically examine network properties. For this case-control study, we analysed 70 children with autism spectrum disorders (52 boys, 18 girls, 38-92 months old) and 19 typically developing children (16 boys, 3 girls, 48-88 months old). After assessing the participants' social reciprocity using the Social Responsiveness Scale, we constructed graphs of functional brain networks from frequency band separated task-free magnetoencephalography recordings. Nodes corresponded to Desikan-Killiany atlas-based 68 brain regions. Edges corresponded to phase lag index values between pairs of brain regions. To elucidate the effects of the existence of interictal epileptiform discharges on graph metrics, we matched each of three pairs from three groups (typically developing children, children with autism spectrum disorders who had interictal epileptiform discharges and those who did not) in terms of age and sex. We used a coarsened exact matching algorithm and applied adjusted regression analysis. We also investigated the relation between social reciprocity and the graph metric. Results show that, in children with autism spectrum disorders, the average clustering coefficient in the theta band was significantly higher in children who had interictal epileptiform discharges. Moreover, children with autism spectrum disorders who had no interictal epileptiform discharges had a significantly lower average clustering coefficient in the theta band than typically developing children had. However, the difference between typically developing children and children with autism spectrum disorder who had interictal epileptiform discharges was not significant. Furthermore, the higher average clustering coefficient in the theta band corresponded to severe autistic symptoms in children with autism spectrum disorder who had interictal epileptiform discharges. However, the association was not significant in children with autism spectrum disorders who had no interictal epileptiform discharge. In conclusion, results demonstrate that alteration of functional brain networks in children with autism spectrum disorders depends on the existence of interictal epileptiform discharges. Interictal epileptiform discharges might 'normalize' the deviation of altered brain networks in autism spectrum disorders, increasing the clustering coefficient. However, when the effect exceeds tolerance, it actually exacerbates autistic symptoms.

Epilepsy and electroencephalographic abnormalities in patients with diagnosis of idiopathic autism spectrum disorder in Medellín

The objective of the present study was to make a clinical and electroencephalographic characterization of the electrical findings and types of seizures in patients with idiopathic autism. Pediatric patients of any age, with the diagnosis of idiopathic ASD, contained within the database of the research “Genetic in autism” were included. An electroencephalographic recording with epilepsy protocol was performed in all the patients. 20 pediatric patients were included with an age media of 10.5 years, SD 5.48 years. The median age for the diagnosis of ASD was 53 months, and epileptic seizures were documented in 45%. 66.6% of patients with epileptic events had anti-epileptic treatment, and only 33.3% had achieved seizure control with medication. Interictal abnormal EEG records were found in 8 patients (40%), with 6 of them having epileptic seizures. The abnormal EEG activity was multifocal in 62.5%, focal in 25% and generalized in 12.5% of the cases. The most frequently compromised location was the temporal lobe.

Seizures and Epilepsy in Autism Spectrum Disorder

Epilepsy and autism frequently co-occur. Epilepsy confers an increased risk of autism and autism confers an increased risk of epilepsy. Specific epilepsy syndromes, intellectual disability, and female gender present a particular risk of autism in individuals with epilepsy. Epilepsy and autism are likely to share common etiologies, which predispose individuals to either or both conditions. Genetic factors, metabolic disorders, mitochondrial disorders, and immune dysfunction all can be implicated.

EEG Correlates of Cognitive Functions and Neuropsychiatric Disorders: A Review of Oscillatory Activity and Neural Synchrony Abnormalities

Background:

A large body of evidence suggested that disruption of neural rhythms and synchronization of brain oscillations are correlated with a variety of cognitive and perceptual processes. Cognitive deficits are common features of psychiatric disorders that complicate treatment of the motivational, affective and emotional symptoms.

Objective:

Electrophysiological correlates of cognitive functions will contribute to understanding of neural circuits controlling cognition, the causes of their perturbation in psychiatric disorders and developing novel targets for the treatment of cognitive impairments.

Methods:

This review includes a description of brain oscillations in Alzheimer’s disease, bipolar disorder, attention-deficit/hyperactivity disorder, major depression, obsessive compulsive disorders, anxiety disorders, schizophrenia and autism.

Results:

The review clearly shows that the reviewed neuropsychiatric diseases are associated with fundamental changes in both spectral power and coherence of EEG oscillations.

Conclusion:

In this article, we examined the nature of brain oscillations, the association of brain rhythms with cognitive functions and the relationship between EEG oscillations and neuropsychiatric diseases. Accordingly, EEG oscillations can most likely be used as biomarkers in psychiatric disorders.

Electroencephalography in Assessment of Autism Spectrum Disorders: A Review

Electroencephalography (EEG) can further out our understanding of autistic spectrum disorders (ASD) neurophysiology. Epilepsy and ASD comorbidity range between 5 and 46%, but its temporal relationship, causal mechanisms and interplay with intellectual disability are still unknown. Epileptiform discharges with or without seizures go as high as 60%, and associate with epileptic encephalopathies, conceptual term suggesting that epileptic activity can lead to cognitive and behavioral impairment beyond the underlying pathology. Seizures and ASD may be the result of similar mechanisms, such as abnormalities in GABAergic fibers or GABA receptor function. Epilepsy and ASD are caused by a number of genetic disorders and variations that induce such dysregulation. Similarly, initial epilepsy may influence synaptic plasticity and cortical connection, predisposing a growing brain to cognitive delays and behavioral abnormalities. The quantitative EEG techniques could be a useful tool in detecting and possibly measuring dysfunctions in specific brain regions and neuronal regulation in ASD. Power spectra analysis reveals a U-shaped pattern of power abnormalities, with excess power in the low and high frequency bands. These might be the consequence of a complicated network of neurochemical changes affecting the inhibitory GABAergic interneurons and their regulation of excitatory activity in pyramidal cells. EEG coherence studies of functional connectivity found general local over-connectivity and long-range under-connectivity between different brain areas. GABAergic interneuron growth and connections are presumably impaired in the prefrontal and temporal cortices in ASD, which is important for excitatory/inhibitory balance. Recent advances in quantitative EEG data analysis and well-known epilepsy ASD co-morbidity consistently indicate a role of aberrant GABAergic transmission that has consequences on neuronal organization and connectivity especially in the frontal cortex.

Seizures in Fragile X Syndrome: Associations and Longitudinal Analysis of a Large Clinic-Based Cohort

Fragile X syndrome (FXS), the most common inherited cause of intellectual disability, learning disability, and autism spectrum disorder, is associated with an increased prevalence of certain medical conditions including seizures. The goal of this study was to better understand seizures in individuals with FXS using the Fragile X Online Registry with Accessible Research Database, a multisite observational study initiated in 2012 involving FXS clinics in the Fragile X Clinic and Research Consortium. Seizure data were available for 1,607 participants, mostly male (77%) and white (74.5%). The overall prevalence of at least one seizure was 12%, with this rate being significantly higher in males than females (13.7 vs. 6.2%, p < 0.001). As compared to individuals with FXS without seizures, those with seizures were more likely to have autism spectrum disorder, current sleep apnea, later acquisition of expressive language, more severe intellectual disability, hyperactivity, irritability, and stereotyped movements. The mean age of seizure onset was 6.4 (SD 6.1) years of age with the great majority (>80%) having onset of seizures which was before 10. For those with epilepsy, about half (52%) had seizures for more than 3 years. This group was found to have greater cognitive and language impairment, but not behavioral disruptions, compared with those with seizures for <3 years. Antiepileptic drugs were more often used in males (60.6%) than females (34.8%), and females more often required more than one medication. The most commonly used anticonvulsants were oxcarbazepine, valproic acid, lamotrigine, and levetiracetam. The current study is the largest and first longitudinal study ever conducted to describe seizures in FXS. Overall, this study confirms previous reports of seizures in FXS and extends previous findings by further defining the cognitive and behavioral phenotype of those with epilepsy in FXS. Future studies should further investigate the natural history of seizures in FXS and the characteristics of seizures in FXS in adulthood.

Sleep and Epilepsy Link by Plasticity

We aimed to explore the link between NREM sleep and epilepsy. Based on human and experimental data we propose that a sleep-related epileptic transformation of normal neurological networks underlies epileptogenesis. Major childhood epilepsies as medial temporal lobe epilepsy (MTLE), absence epilepsy (AE) and human perisylvian network (PN) epilepsies - made us good models to study. These conditions come from an epileptic transformation of the affected functional systems. This approach allows a system-based taxonomy instead of the outworn generalized-focal classification. MTLE links to the memory-system, where epileptic transformation results in a switch of normal sharp wave-ripples to epileptic spikes and pathological high frequency oscillations, compromising sleep-related memory consolidation. Absence epilepsy (AE) and juvenile myoclonic epilepsy (JME) belong to the corticothalamic system. The burst-firing mode of NREM sleep normally producing sleep-spindles turns to an epileptic working mode ejecting bilateral synchronous spike-waves. There seems to be a progressive transition from AE to JME. Shared absences and similar bilateral synchronous discharges show the belonging of the two conditions, while the continuous age windows - AE affecting schoolchildren, JME the adolescents - and the increased excitability in JME compared to AE supports the notion of progression. In perisylvian network epilepsies - idiopathic focal childhood epilepsies and electrical status epilepticus in sleep including Landau-Kleffner syndrome - centrotemporal spikes turn epileptic, with the potential to cause cognitive impairment. Postinjury epilepsies modeled by the isolated cortex model highlight the shared way of epileptogenesis suggesting the derailment of NREM sleep-related homeostatic plasticity as a common step. NREM sleep provides templates for plasticity derailing to epileptic variants under proper conditions. This sleep-origin explains epileptiform discharges' link and similarity with NREM sleep slow oscillations, spindles and ripples. Normal synaptic plasticity erroneously overgrowing homeostatic processes may derail toward an epileptic working-mode manifesting the involved system's features. The impact of NREM sleep is unclear in epileptogenesis occurring in adolescence and adulthood, when plasticity is lower. The epileptic process interferes with homeostatic synaptic plasticity and may cause cognitive impairment. Its type and degree depends on the affected network's function. We hypothesize a vicious circle between sleep end epilepsy. The epileptic derailment of normal plasticity interferes with sleep cognitive functions. Sleep and epilepsy interconnect by the pathology of plasticity.

Electroencephalographic Abnormalities in Autism Spectrum Disorder: Characteristics and Therapeutic Implications

A large body of literature reports the higher prevalence of epilepsy in subjects with Autism Spectrum Disorder (ASD) compared to the general population. Similarly, several studies report an increased rate of Subclinical Electroencephalographic Abnormalities (SEAs) in seizure-free patients with ASD rather than healthy controls, although with varying percentages. SEAs include both several epileptiform discharges and different non-epileptiform electroencephalographic abnormalities. They are more frequently associated with lower intellectual functioning, more serious dysfunctional behaviors, and they are often sign of severer forms of autism. However, SEAs clinical implications remain controversial, and they could represent an epiphenomenon of the neurochemical alterations of autism etiology. This paper provides an overview of the major research findings with two main purposes: to better delineate the state-of-the-art about EEG abnormalities in ASD and to find evidence for or against appropriateness of SEAs pharmacological treatment in ASD.

Seizures and Epilepsy in Autism Spectrum Disorder

Epilepsy and autism frequently co-occur. Epilepsy confers an increased risk of autism and autism confers an increased risk of epilepsy. Specific epilepsy syndromes, intellectual disability, and female gender present a particular risk of autism in individuals with epilepsy. Epilepsy and autism are likely to share common etiologies, which predispose individuals to either or both conditions. Genetic factors, metabolic disorders, mitochondrial disorders, and immune dysfunction all can be implicated.

Genetic backgrounds have unique seizure response profiles and behavioral outcomes following convulsant administration

Three highly utilized strains of mice, common for preclinical genetic studies, were evaluated for seizure susceptibility and behavioral outcomes common to the clinical phenotypes of numerous psychiatric disorders following repeated low-dose treatment with either a gamma-aminobutyric acid (GABA) receptor antagonist (pentylenetetrazole (PTZ)) or a glutamate agonist (kainic acid (KA)). Effects of strain and treatment were evaluated with classic seizure scoring and a tailored behavior battery focused on behavioral domains common in neuropsychiatric research: learning and memory, social behavior, and motor abilities, as well as seizure susceptibility and/or resistance. Seizure response was induced by a single daily treatment of either PTZ (30 mg/kg, intraperitoneally (i.p.)) or KA (5 mg/kg, i.p.) for 10 days. Pentylenetetrazole-treated FVB/NJ and C57BL/6NJ strains of mice showed strong, clear seizure responses. This also resulted in cognitive and social deficits, and increased susceptibility to a high dose of PTZ. Kainic acid-treated FVB/NJ and C57BL/6NJ strains of mice had a robust seizure response, which resulted in hyperactivity. Pentylenetetrazole-treated C57BL/6J mice demonstrated mild hyperactivity, while KA-treated C57BL/6J displayed cognitive deficits and resistance to a high dose of KA but no social deficits. Overall, a uniquely different seizure response profile was detected in the C57BL/6J strain with few observable instances of seizure response despite repeated convulsant administration by two mechanisms. This work illustrated that differing background genetic strains have unique seizure susceptibility profiles and distinct social and cognitive behavior following PTZ and/or KA treatment and that it is, therefore, necessary to consider strain differences before attributing behavioral phenotypes to gene(s) of interest during preclinical evaluations of genetic mouse models, especially when outcome measures are focused on cognitive and/or social behaviors common to the clinical features of numerous neurological disorders.

EEG Abnormalities as a Neurophysiological Biomarker of Severity in Autism Spectrum Disorder: A Pilot Cohort Study

To date, the phenotypic significance of EEG abnormalities in patients with ASD is unclear. In a population affected by ASD we aimed to evaluate: the phenotypic characteristics; the prevalence of EEG abnormalities; the potential correlations between EEG abnormalities and behavioral and cognitive variables. Sixty-nine patients with ASD underwent cognitive or developmental testing, language assessment, and adaptive behavior skills evaluation as well as sleep/wake EEG recording. EEG abnormalities were found in 39.13% of patients. EEG abnormalities correlated with autism severity, hyperactivity, anger outbursts, aggression, negative or destructive behavior, motor stereotypies, intellectual disability, language impairment and self-harm. Our findings confirmed that EEG abnormalities are present in the ASD population and correlate with several associated phenotypic features.

Association between Interictal Epileptiform Discharges and Autistic Spectrum Disorder

It has been reported that bioelectric alterations in an electroencephalogram (EEG) may play an etiological role in neurodevelopmental disorders. The clinical impact of interictal epileptiform discharges (IEDs) in association with autistic spectrum disorder (ASD) is unknown. The Autism Diagnostic Interview-Revised (ADI-R) is one of the gold standards for the diagnosis of autistic spectrum disorder. Some studies have indicated high comorbidity of IED and ASD, while other studies have not supported an association between the central symptoms of autism and IED. This review examines the high comorbidity and clinical impact of IED; patients with epilepsy are excluded from the scope of this review. ASD can be disabling and is diagnosed at an average age of 5 years old, at which point the greatest neurological development has occurred. If an association between IED and ASD is identified, a clinical tool that entails an innocuous procedure could enable diagnosis in the first years of life. However, in the absence of reports that prove an association between IED and ASD, patients should not be subjected to expensive treatments, such as the administration of anticonvulsant therapies.

Autistic spectrum disorder and epilepsy: diagnostic challenges

Introduction: Epilepsy is more frequent in individuals with Autism Spectrum Disorder (ASD) than in the general population; however, its diagnosis is frequently challenging. Areas Covered: We report the current diagnostic criteria for both ASD and epilepsy. We describe the incidence, prevalence, and risk factors for epilepsy in patients with ASD. We then focus on the electro-clinical approach, including the clinical evaluation of cognitive regression. Expert Opinion: A diagnosis of epilepsy should be made based on the International League Against Epilepsy (ILAE) definition. A diagnosis of epilepsy should be established based on a single seizure with electroencephalography (EEG) abnormalities. Considering the high prevalence of EEG abnormalities in children with ASD without epilepsy, EEG should only be performed at epilepsy onset, and more precisely when a clinical interview has confirmed that repetitive paroxysmal events could be seizures. There are still many gaps in our understanding of epilepsy in patients with ASD. It would be of interest to further understand the links, if any, between EEG abnormalities and ASD phenotype. The identification of epilepsy syndromes in ASD would help analyze the possible underlying etiologies, for the administration of more appropriate antiepileptic drugs (AED), and to explain the prognosis to caregivers.

Electroencephalogram (EEG) for children with autism spectrum disorder: evidential considerations for routine screening

Routine electroencephalograms (EEG) are not recommended as a screen for epileptic discharges (EDs) in current practice guidelines for children with autism spectrum disorder (ASD). However, a review of the research from the last three decades suggests that this practice should be reevaluated. The significant comorbidity between epilepsy and ASD, its shared biological pathways, risk for developmental regression, and cognitive challenges demand increased clinical investigation requiring a proactive approach. This review highlights and explains the need for screening EEGs for children with ASD. EEG would assist in differentiating EDs from core features of ASD and could be included in a comprehensive assessment. EEG also meets the demand for evidence-based precision medicine and focused care for the individual, especially when overlapping processes of development are present.

Epilepsy and interictal epileptiform activity in patients with autism spectrum disorders

PURPOSE

The purpose of this study was to determine the prevalence of epilepsy and subclinical epileptiform abnormalities in children with autism spectrum disorder (ASD), and to investigate its effects on core autistic symptoms and adaptive behavior skills.

METHODS

Patients with diagnosis of ASD who met full criteria on Autism Diagnostic Interview-Revised (ADI-R) were included in the study. Adaptive behavior skills were assessed by Vineland Adaptive Behavior Scale-II (VABS-II). Clinical assessment for epilepsy and video electroencephalography (EEG) (v-EEG) examinations during wakefulness and/or sleep were prospectively performed in all patients.

RESULTS

A total of 112 patients with diagnosis of ASD of mean age 6.58 ± 3.72 were included in the study. Based on clinical and v-EEG assessments, three groups of patients were defined: 1) patients with epilepsy (n = 17; 15.2%); 2) patients with epileptiform discharges in absence of clinical seizures (n = 14; 12.5%); 3) patients without epilepsy and without epileptiform discharges (n = 81; 72.3%). There were no significant differences between three groups of patients on ADI-R subscores. Speech development was also not significantly related to epilepsy. There was a slight tendency of the VABS-II motor skills score to be higher in the group of patients with autism without clinical diagnosis of epilepsy and without subclinical epileptiform discharges (p < 0.05) in comparison with the two other groups. According to this tendency, we might claim that patients with higher scores on motor skills could have 0.88 times lower odds for having epileptiform EEG activity.

CONCLUSIONS

According to our results, we were not able to detect differences in the ADI-R between the three populations with ASD, all with unknown etiology. Epilepsy, as well as subclinical epileptic discharges, showed small effects on Motor Skills in patients with autism, and had no effect on adaptive behavior Communication/Socialization/Daily Living Skills.

Epilepsy as a derailment of sleep plastic functions may cause chronic cognitive impairment - A theoretical review

We report on a peculiar way of chronic cognitive impairment associated with interictal epileptic activity during NREM sleep. We review three major groups of epilepsy: mesiotemporal epilepsy (MTLE) involving the epileptic derailment of the hippocampal declarative memory system; childhood developmental epileptic encephalopathies; and the spectrum disorders of the perisylvian communication network with the centrotemporal spike phenomenon, overarching child- and adulthood epilepsies, totaling up the majority of epilepsies in childhood. We outline high impact research-lines on the cognitive harm of epilepsy; causing specific or global cognitive decline through its interference with sleep plastic functions. We highlight the key role of interictal activity in the development of cognitive impairment and the fact that we are unarmed against this harm, antiepileptic pharmaco-therapy being ineffective against the interictal process marked by spikes and high frequency oscillations.

Strong relationship between NREM sleep, epilepsy and plastic functions - A conceptual review on the neurophysiology background

The aim of this review is to summarize and discuss the strong bond between NREM sleep and epilepsy underlain by the shared link and effect on brain plasticity. Beyond the seizure occurrence rate, sleep relatedness may manifest in the enhancement of interictal epileptic discharges (spikes and pathological ripples). The number of the discharges as well as their propagation increase during NREM sleep, unmasking the epileptic network that is hidden during wakefulness. The interictal epileptic discharges associate with different sleep constituents (sleep slow waves, spindling and high frequency oscillations); known to play essential role in memory and learning. We highlight three major groups of epilepsies, in which sleep-related plastic functions suffer an epileptic derailment. In absence epilepsy mainly involving the thalamo-cortical system, sleep spindles transform to generalized spike-wave activity. In mesio-temporal epilepsy affecting the hippocampal declarative memory system, the sharp wave ripples derail to dysfunctional epileptic oscillations (spikes and pathological ripples). Idiopathic childhood epilepsies affecting the perisylvian network may progress to catastrophic status electricus during NREM sleep. In these major epilepsies, NREM sleep has a pivotal role in the development and course of the disorder. Epilepsy is born in-, and exhibits its pathological properties during NREM sleep. Interictal discharges are important causative agents in this process.

EEG endophenotypes in autism spectrum disorder

OBJECTIVES

The association between autism spectrum disorder (ASD) and epilepsy is well-known. Abnormalities on electroencephalography (EEG) results have been reported in patients with ASD without a history of seizures. However, little is known about the relationship between abnormalities on EEG results and the core features of ASD. The purpose of the study was to determine the relationship between the presence of epilepsy and/or abnormalities on EEG results and disease-associated impairments in young children with ASD.

METHODS

Data were collected from medical records at Cincinnati Children's Hospital Medical Center (CCHMC) of patients with well-characterized ASD. Patients were subdivided into three groups: ASD without epilepsy but with abnormal EEG results, ASD without epilepsy and normal EEG results, and ASD with epilepsy. Developmental (Mullen Scales of Early Learning (MSEL)), adaptive (Vineland Adaptive Behavior Scales (VABS)), behavioral (Child Behavior Checklist), and language (Preschool Language Scales (PLS)) assessments, along with birth and developmental histories, medications, and medical comorbidities were collected. Electroencephalography data were abstracted from reports and included presence, characterization, and location of abnormalities.

RESULTS

Analysis was performed on 443 patients with ASD. Seventy patients (15.8%) had epilepsy at the time of ASD diagnosis. Out of 372 patients with ASD and no epilepsy, 95 (25.5%) had an abnormal EEG result (67.4% epileptiform, 36.8% other abnormalities). Majority of epileptiform discharges were focal (83%) and most commonly seen in the left temporal region. The group with abnormal EEG results exhibited more impaired adaptive functioning when compared with the group with normal EEG results (p < 0.05). The group with abnormal EEG results was more similar to the group with epilepsy, differing only in expressive language (p < 0.01) and fine motor (p < 0.05) skills on the Mullen Scales. The group with epilepsy exhibited lower scores in all areas of developmental and adaptive functioning compared with the group with normal EEG results (p < 0.05). At the time of analysis, 13 patients (8 in the group with abnormal EEG results, 5 in the group with normal EEG results) developed epilepsy at a mean age of 10.5 years ± 3.3 years.

CONCLUSIONS

The presence of an abnormal EEG result or epilepsy in the setting of ASD suggests worse developmental and adaptive functioning. Further analysis will help to clarify associations and offer insight into treatment for this subpopulation without epilepsy but with abnormal EEG results.

Association Between Magnetoencephalographic Interictal Epileptiform Discharge and Cognitive Function in Young Children With Typical Development and With Autism Spectrum Disorders

Electroencephalograms of individuals with autism spectrum disorders (ASD) show higher rates of interictal epileptiform discharges (IEDs), which are known to have an inverse association with cognitive function in typically developed (TD) children. Nevertheless, that phenomenon has not been investigated adequately in children with ASD. From university and affiliated hospitals, 163 TD children (84 male, 79 female, aged 32-89 months) and 107 children (85 male, 22 female, aged 36-98 months) with ASD without clinical seizure were recruited. We assessed their cognitive function using the Kaufman Assessment Battery for Children (K-ABC) and recorded 10 min of MEG. Original waveforms were visually inspected. Then a linear regression model was applied to evaluate the association between the IED frequency and level of their cognitive function. Significantly higher rates of IEDs were found in the ASD group than in the TD group. In the TD group, we found significant negative correlation between mental processing scale scores (MPS) and the IED frequency. However, for the ASD group, we found significant positive correlation between MPS scores and the IED frequency. In terms of the achievement scale, correlation was not significant in either group. Although we found a correlative rather than a causal effect, typically developed children with higher IED frequency might better be followed up carefully. Furthermore, for children with ASD without clinical seizure, clinicians might consider IEDs as less harmful than those observed in TD children.

Risk of Second Seizure in Pediatric Patients With Idiopathic Autism

PURPOSE

Epilepsy is a comorbidity of idiopathic autism spectrum disorder. The aim was to characterize the risk and time of second seizure in children with idiopathic autism spectrum disorder.

METHODS

A retrospective review was performed at the University of Chicago and NorthShore University HealthSystem. Patients with idiopathic autism spectrum disorder, ≥1 seizure, and age 2 to 23 years were included.

RESULTS

153 patients were included; 141 (92%) had a second seizure. The average age at first seizure was 7.14 years (median: 5.08 years) and 8.12 years (median: 7.3 years) at second seizure. Average time between first and second seizure was 7.68 months.

DISCUSSION

A high risk of seizure recurrence was found in this population. There was a short time to second seizure, with most having a recurrence within 1 year. These findings may be used to guide therapy in children with autism spectrum disorder and epilepsy.

Neuromagnetic responses to tactile stimulation of the fingers: Evidence for reduced cortical inhibition for children with Autism Spectrum Disorder and children with epilepsy

The purpose of this study was to compare somatosensory responses from a group of children with epilepsy and a group of children with autism spectrum disorder (ASD), with age matched TD controls. We hypothesized that the magnitude of the tactile "P50m" somatosensory response would be reduced in both patient groups, possibly due to reduced GABAergic signaling as has been implicated in a variety of previous animal models and in vivo human MRS studies. We observed significant (~ 25%) decreases in tactile P50m dipole moment values from the source localized tactile P50m response, both for children with epilepsy and for children with ASD. In addition, the latency of the tactile P50m peak was observed to be equivalent between TD and ASD groups but was significantly delayed in children with epilepsy by ~ 6 ms. Our data support the hypothesis of impaired GABAergic signaling in both children with ASD and children with epilepsy. Further work is needed to replicate these findings and directly relate them to both in vivo measures of GABA via e.g. magnetic resonance spectroscopy and psychophysical assessments of somatosensory function, and behavioral indices.

Annual Research Review: Understudied populations within the autism spectrum - current trends and future directions in neuroimaging research

BACKGROUND

Autism spectrum disorders (ASDs) are a heterogeneous group of neurodevelopmental conditions that vary in both etiology and phenotypic expression. Expressions of ASD characterized by a more severe phenotype, including autism with intellectual disability (ASD + ID), autism with a history of developmental regression (ASD + R), and minimally verbal autism (ASD + MV) are understudied generally, and especially in the domain of neuroimaging. However, neuroimaging methods are a potentially powerful tool for understanding the etiology of these ASD subtypes.

SCOPE AND METHODOLOGY

This review evaluates existing neuroimaging research on ASD + MV, ASD + ID, and ASD + R, identified by a search of the literature using the PubMed database, and discusses methodological, theoretical, and practical considerations for future research involving neuroimaging assessment of these populations.

FINDINGS

There is a paucity of neuroimaging research on ASD + ID, ASD + MV, and ASD + R, and what findings do exist are often contradictory, or so sparse as to be ungeneralizable. We suggest that while greater sample sizes and more studies are necessary, more important would be a paradigm shift toward multimodal (e.g. imaging genetics) approaches that allow for the characterization of heterogeneity within etiologically diverse samples.

Altered Intermittent Rhythmic Delta and Theta Activity in the Electroencephalographies of High Functioning Adult Patients with Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is often associated with epilepsy. Previous studies have also shown increased rates of electroencephalographic (EEG) alteration in ASD patients without epilepsy. The aim of this study was to compare the rate of intermittent rhythmic delta and theta activity (IRDA/IRTA) events between high-functioning adult patients with ASD and matched healthy controls. Materials and Methods: Routine EEG records of 19 ASD patients and 19 matched controls were screened for IRDA/IRTA using a fully data driven analysis with fixed thresholds. IRDA/IRTA rates before and after hyperventilation (HV) as well as the HV-induced difference in IRDA/IRTA rates (HV difference) were analyzed. For inter-group measures, we used the Wilcoxon rank sum test. Results: Significantly increased HV difference was detected in the ASD group (p = 0.0497). However, the groups showed no difference in IRDA/IRTA rates before HV (p = 0.564) and after HV (p = 0.163). Conclusions: The lack of any group differences regarding IRDA/IRTA before HV might be related to the fact that we only studied non-secondary high-functioning autism in a small sample of epilepsy-free adult patients. A significantly increased HV difference might be regarded as a marker of subtle neuronal network instability possibly causing short-term disturbances via local area network inhibition and long-term effects via epileptic encephalopathy.

Bidirectional association between autism spectrum disorder and epilepsy in child and adolescent patients: a population-based cohort study

This study aimed to assess whether there is a bidirectional association between autism spectrum disorder (ASD) and epilepsy in child and adolescent patients. The National Health Insurance Research Database of Taiwan was used to conduct two cohort studies of patients who were under 18 years of age during the period 1997-2008. Cohort 1 comprised patients with newly diagnosed ASD but excluded those diagnosed with epilepsy prior to ASD. A non-ASD comparison group was matched to each case in terms of age and sex. Cohort 2 comprised patients with newly diagnosed epilepsy but excluded those diagnosed with ASD prior to epilepsy. A non-epilepsy comparison group was matched to each case in terms of age and sex. We calculated the incidence of epilepsy in patients with ASD and hazard ratio (HR) to estimate the risk of epilepsy in association with ASD in cohort 1, and the reverse in cohort 2. In cohort 1, the incidence of epilepsy was 13.7 in the ASD group and 1.3 in the non-ASD group (per 1000 person-years). The adjusted HR for epilepsy was 8.4 (95 % CI 5.5-12.7) in the ASD group when compared with the non-ASD group. In cohort 2, the incidence of ASD was 3.4 in the epilepsy group and 0.3 in the non-epilepsy group (per 1000 person-years). The adjusted HR for ASD was 8.4 (95 % CI 6.2-11.4) in the epilepsy group when compared with the non-epilepsy group. A bidirectional association was, therefore, found to exist between ASD and epilepsy. These findings implicate that ASD and epilepsy probably share common risk factors. However, further studies are required to reveal more detail on the mechanism of this bidirectional association.

Measuring neural excitation and inhibition in autism: Different approaches, different findings and different interpretations

The balance of neural excitation and inhibition (E/I balance) is often hypothesised to be altered in autism spectrum disorder (ASD). One widely held view is that excitation levels are elevated relative to inhibition in ASD. Understanding whether, and how, E/I balance may be altered in ASD is important given the recent interest in trialling pharmacological interventions for ASD which target inhibitory neurotransmitter function. Here we provide a critical review of evidence for E/I balance in ASD. We conclude that data from a number of domains provides support for alteration in excitation and inhibitory neurotransmission in ASD, but when considered collectively, the available literature provide little evidence to support claims for either a net increase in excitation or a net increase in inhibition. Strengths and limitations of available techniques are considered, and directions for future research discussed.

Neural Rhythmicity, Feature Binding, and Serotonin: A Hypothesis

Natural selection favors animals that make successful predictive theories about the world. The first step in the formation of these theories is the construction of complex, multifea ture percepts. This process requires resolution of the binding problem, possibly via rhyth mic cortical oscillations, as suggested by von der Malsburg, Singer, Koch & Crick, and others. If the binding process were made rewarding, animals might enjoy theory-making and spontaneously become "smarter." I argue that the serotonergic raphe may have been used by evolution to link cortical binding with limbic reward centers and so serve as a neural substrate for the enjoyment of successful theory-making. I present evidence, from the study of such disorders as obsessive-compulsive disorder and autism and such drugs as d-lysergic acid diethylamide (LSD) and 3,4-methylenedioxymethamphetamine (MDMA), suggesting that rhythmicity, reward, and pattern recognition are causally linked. I also propose that the genus Homo has tied powerful symbol manipulation hardware ("language") to the binding/theory-making circuits, allowing the construction, rehearsal, and communication of sophisticated models of the world. I suggest that many interesting phenomena, such as music-induced euphoria, déjà vu, and the so-called "temporal lobe personality" can be explained by the interactions between these systems. NEURO SCIENTIST 5:79-85, 1999

Maternal Stress Combined with Terbutaline Leads to Comorbid Autistic-Like Behavior and Epilepsy in a Rat Model

Human autism is comorbid with epilepsy, yet, little is known about the causes or risk factors leading to this combined neurological syndrome. Although genetic predisposition can play a substantial role, our objective was to investigate whether maternal environmental factors alone could be sufficient. We examined the independent and combined effects of maternal stress and terbutaline (used to arrest preterm labor), autism risk factors in humans, on measures of both autistic-like behavior and epilepsy in Sprague-Dawley rats. Pregnant dams were exposed to mild stress (foot shocks at 1 week intervals) throughout pregnancy. Pups were injected with terbutaline on postnatal days 2-5. Either maternal stress or terbutaline resulted in autistic-like behaviors in offspring (stereotyped/repetitive behaviors and deficits in social interaction or communication), but neither resulted in epilepsy. However, their combination resulted in severe behavioral symptoms, as well as spontaneous recurrent convulsive seizures in 45% and epileptiform spikes in 100%, of the rats. Hippocampal gliosis (GFAP reactivity) was correlated with both abnormal behavior and spontaneous seizures. We conclude that prenatal insults alone can cause comorbid autism and epilepsy but it requires a combination of teratogens to achieve this; testing single teratogens independently and not examining combinatorial effects may fail to reveal key risk factors in humans. Moreover, astrogliosis may be common to both teratogens. This new animal model of combined autism and epilepsy permits the experimental investigation of both the cellular mechanisms and potential intervention strategies for this debilitating comorbid syndrome.

Cortical variability in the sensory-evoked response in autism

Previous findings have shown that individuals with autism spectrum disorder (ASD) evince greater intra-individual variability (IIV) in their sensory-evoked fMRI responses compared to typical control participants. We explore the robustness of this finding with a new sample of high-functioning adults with autism. Participants were presented with visual, somatosensory and auditory stimuli in the scanner whilst they completed a one-back task. While ASD and control participants were statistically indistinguishable with respect to behavioral responses, the new ASD group exhibited greater IIV relative to controls. We also show that the IIV was equivalent across hemispheres and remained stable over the duration of the experiment. This suggests that greater cortical IIV may be a replicable characteristic of sensory systems in autism.

Autism and Epilepsy: Exploring the Relationship Using Experimental Models

The common co-occurrence of autism and epilepsy suggests that certain neurobiological mechanisms are shared between these disorders. In particular, the profusion of novel genetic mutations being discovered in autism and epilepsy points to abnormalities in synapse formation and function that alter the balance between neuronal excitation and inhibition. Animal models can be informative in sorting out the medical and behavioral complexities in autism and epilepsy and the relationship between them. As mechanistic information accrues, it is anticipated that mutation- and pathway-specific targeted treatments can be developed.

Current controversies in the relationships between autism and epilepsy

The controversies that have arisen in endeavoring to establish the nature of the relationships between autism and epilepsy might be summarized in a few simple questions, most of which do not yet have clear, complete answers. Does epilepsy cause autism? Does autism cause epilepsy? Are there underlying brain mechanisms that predispose to both conditions? What is the role of genetics in this regard? What is the importance of prenatal, perinatal, and postnatal environmental factors? Do any of the proposed relationships between autism and epilepsy provide insight into useful management or treatment? Is the prognosis of either autism or epilepsy different when the other condition is also present? What is the role of additional comorbidities, such as intellectual impairment or attention deficit hyperactivity disorder, in the relationship between the two conditions and in influencing treatment choices? From the evidence currently available, it would appear that epilepsy can rarely be the cause of autistic features but is not the cause of autism in most cases. There is currently no credible mechanism for suggesting that autism might cause epilepsy. There is strong evidence for an underlying predisposition for both conditions, particularly arising from genetic investigations. However, many issues remain unresolved. Considering the amount of research that has been published in this area, it is surprising that so few definitive answers have been established. The papers in this issue's special section provide additional insights into the relationships between autism and epilepsy; while they do not provide answers to all the questions, they represent considerable progress in this area and, at the very least, give some strong indication of what research might, in the future, provide such answers.

Clinical characteristics of children and young adults with co-occurring autism spectrum disorder and epilepsy

The association between autism spectrum disorder (ASD) and epilepsy has been described for decades, and yet we still lack the full understanding of this relationship both clinically and at the pathophysiologic level. This review evaluates the available data in the literature pertaining to the clinical characteristics of patients with autism spectrum disorder who develop epilepsy and, conversely, patients with epilepsy who develop autism spectrum disorder. Many studies demonstrate an increased risk of epilepsy in individuals with ASD, but rates vary widely. This variability is likely secondary to the different study methods employed, including the study population and definitions of the disorders. Established risk factors for an increased risk of epilepsy in patients with ASD include intellectual disability and female gender. There is some evidence of an increased risk of epilepsy associated with other factors such as ASD etiology (syndromic), severity of autistic features, developmental regression, and family history. No one epilepsy syndrome or seizure type has been associated, although focal or localization-related seizures are often reported. The age at seizure onset can vary from infancy to adulthood with some evidence of a bimodal age distribution. The severity and intractability of epilepsy in populations with ASD have not been well studied, and there is very little investigation of the role that epilepsy plays in the autism behavioral phenotype. There is evidence of abnormal EEGs (especially epileptiform abnormalities) in children with ASD even in the absence of clinical seizures, but very little is known about this phenomenon and what it means. The development of autism spectrum disorder in patients with epilepsy is less well studied, but there is evidence that the ASD risk is greater in those with epilepsy than in the general population. One of the risk factors is intellectual disability, and there is some evidence that the presence of a particular seizure type, infantile spasms, may increase risk, but some of the data are conflicting. We believe that one of the reasons that so little is known about this phenomenon is the lack of cross talk between researchers and clinicians alike in the two fields. We conclude that large systematic studies that employ strict ascertainment of samples using standardized definitions of both disorders, validated data collection tools, and appropriate longitudinal follow-up are needed to better shed light on certain clinical aspects of the comorbidity of ASD and epilepsy. Ideally, we could provide the optimal diagnostic and treatment services to these patients in a multidisciplinary setting with both epilepsy and neurobehavioral specialists. This article is part of a Special Issue entitled "Autism and Epilepsy".

Behavioral correlates of epileptiform abnormalities in autism

There is a high incidence of epileptiform abnormalities in children with autism even in the absence of clinical seizures. These findings are most prominent during sleep recordings. The significance of these abnormalities is unclear. Although studies do not all agree, there may be some association between cognitive function, behavior, and the presence or absence of epileptiform discharges. Small studies of anticonvulsant treatment mostly suggest an improvement in certain aspects of cognitive or behavioral functioning in these children, but larger and more comprehensive studies are needed to determine the potential relationship between epileptiform discharges on EEG, cognitive and behavioral functioning, and treatment effects in the population with autism. This article is part of a Special Issue entitled "Autism and Epilepsy".

Interictal epileptiform activity and autism

Many individuals with autism have epileptiform discharges on their EEG without having definite clinical seizures. The clinical significance of epileptiform activity in patients with autism is controversial. Some consider it an epiphenomenon of the underlying condition that should be ignored, and others believe that frequent spikes may contribute to the cognitive impairment and advocate treatment. Several studies have reported variable rates of epileptiform activity and variable response to treatment. There is an urgent need to conduct controlled clinical trials to assess the true incidence of epileptiform activity in children with autism, develop a risk assessment model, and study the effectiveness of treatment. This article is part of a Special Issue entitled "Autism and Epilepsy".