EEG endophenotypes in autism spectrum disorder

Overnight Electroencephalogram to Forecast Epilepsy Development in Children with Autism Spectrum Disorders

OBJECTIVE

To establish the utility of long-term electroencephalogram (EEG) in forecasting epilepsy onset in children with autism spectrum disorder (ASD).

STUDY DESIGN

A single-institution, retrospective analysis of children with ASD, examining long-term overnight EEG recordings collected over a period of 15 years, was conducted. Clinical EEG findings, patient demographics, medical histories, and additional Autism Diagnostic Observation Schedule data were examined. Predictors for the timing of epilepsy onset were evaluated using survival analysis and Cox regression.

RESULTS

Among 151 patients, 17.2% (n = 26) developed unprovoked seizures (Sz group), while 82.8% (n = 125) did not (non-Sz group). The Sz group displayed a higher percentage of interictal epileptiform discharges (IEDs) in their initial EEGs compared with the non-Sz group (46.2% vs 20.0%, P = .01). The Sz group also exhibited a greater frequency of slowing (42.3% vs 13.6%, P < .01). The presence of IEDs or slowing predicted an earlier seizure onset, based on survival analysis. Multivariate Cox proportional hazards regression revealed that the presence of any IEDs (HR 3.83, 95% CI 1.38-10.65, P = .01) or any slowing (HR 2.78, 95% CI 1.02-7.58, P = .046 significantly increased the risk of developing unprovoked seizures.

CONCLUSION

Long-term EEGs are valuable for predicting future epilepsy in children with ASD. These findings can guide clinicians in early education and potential interventions for epilepsy prevention.

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.

An exploratory study of sleep quality and quantity in children with causal variants in SYNGAP1, an autism risk gene

STUDY OBJECTIVES

Sleep disturbances are reported in 62% of children with SYNGAP1-Intellectual Disability (SYNGAP1-ID), a rare neurodevelopmental disorder characterized by intellectual disability, epilepsy, autism spectrum disorder (ASD), sensory and behavioral challenges. Although Children's Sleep Habits Questionnaire (CSHQ) scores are elevated in children with SYNGAP1-ID factors that predict sleep disturbance are not well understood. The goal of this study is to identify predictors of sleep problems.

METHODS

Parents of 21 children with SYNGAP1-ID completed questionnaires, and 6 children wore the Actiwatch2 for 14 continuous days. Non-parametric analysis of psychometric scales and actigraphy data were performed. Actigraphy derived sleep parameters were compared to controls and rest activity rhythms were assessed using arctools an open-source R package.

RESULTS

CSHQ total sleep scores in children with SYNGAP1-ID and ASD were not different from children with SYNGAP1 without ASD (p = 0.61). Sleep anxiety (β 1.646, 95% CI 0.9566 to 2.336) and parasomnias (β 0.6294, 95% CI 0.06423 to 1.195) were strong predictors of bedtime resistance (R2 = 0.767, p < 0.001). The sedentary to active transition probability during the 12-18 h epoch (β = 0.004, p = 0.008, R2 = 0.85) and the duration of the active bout during the 18-24 h epoch (β = 0.166, p = 0.029, R2 = 0.74) were strong predictors of total sleep disturbance.

CONCLUSION

The CSHQ may be a reliable measure of sleep difficulties in children with SYNGAP1-ID. Sleep anxiety, parasomnias and difficulty winding-down are significant contributors to sleep disturbances.

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.

EEG Features in Autism Spectrum Disorder: A Retrospective Analysis in a Cohort of Preschool Children

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder that can be associated with intellectual disability (ID) and epilepsy (E). The etiology and the pathogenesis of this disorder is in most cases still to be clarified. Several studies have underlined that the EEG recordings in children with these clinical pictures are abnormal, however the precise frequency of these abnormalities and their relationship with the pathogenic mechanisms and in particular with epileptic seizures are still unknown. We retrospectively reviewed 292 routine polysomnographic EEG tracings of preschool children (age < 6 years) who had received a first multidisciplinary diagnosis of ASD according to DSM-5 clinical criteria. Children (mean age: 34.6 months) were diagnosed at IRCCS E. Medea (Bosisio Parini, Italy). We evaluated: the background activity during wakefulness and sleep, the presence and the characteristics (focal or diffuse) of the slow-waves abnormalities and the interictal epileptiform discharges. In 78.0% of cases the EEG recordings were found to be abnormal, particularly during sleep. Paroxysmal slowing and epileptiform abnormalities were found in the 28.4% of the subjects, confirming the high percentage of abnormal polysomnographic EEG recordings in children with ASD. These alterations seem to be more correlated with the characteristics of the underlying pathology than with intellectual disability and epilepsy. In particular, we underline the possible significance of the prevalence of EEG abnormalities during sleep. Moreover, we analyzed the possibility that EEG data reduces the ASD clinical heterogeneity and suggests the exams to be carried out to clarify the etiology of the disorder.

Autism with Epilepsy: A Neuropsychopharmacology Update

The association between autism spectrum disorders (ASD) and epilepsy has been extensively documented, and the estimated prevalence varies depending upon the selected population and the clinical characteristics. Currently, there are a lack of studies assessing the patient care pathways in ASD, particularly for comorbidity with epilepsy, despite its personal, familial, and economic impacts. Genetic abnormalities are likely implicated in the association of ASD and epilepsy, although they are currently detectable in only a small percentage of patients, and some known genetic and medical conditions are associated with ASD and epilepsy. There is no specificity of seizure type to be expected in children and adolescents with ASD compared with other neurodevelopmental disorders or epileptic syndromes. Treatment options include antiepileptic drugs (AED) and developmentally-based early interventions for ASD. Carbamazepine and lamotrigine are the most used AED, but further studies are needed to more precisely define the most suitable medications for this specific group of children with ASD.

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.

Multimorbidity patterns and subgroups among autistic adults with intellectual disability: Results from the EFAAR study

LAY ABSTRACT

Multimorbidity relates to having multiple chronic health conditions. It is a risk factor for poor health and reduces life expectancy. Autistic people have multiple chronic health conditions and die prematurely, especially if they have an intellectual disability (autism spectrum disorder and intellectual disability). Certain pathophysiological processes observed in autism spectrum disorder are common to those related to the genesis and/or maintenance of multimorbidity. Furthermore, multimorbidity could be helpful in better identifying patient subgroups in autism spectrum disorder. It is therefore essential to better characterize multimorbidity and its consequences in the subgroup of autism spectrum disorder + intellectual disability individuals to offer them personalized care. We conducted a preliminary study of 63 autism spectrum disorder + intellectual disability adults to classify them according to their multimorbidity and search for a specific combination of chronic health conditions. We observed high and early multimorbidity in this sample and identified four classes of participants, distinguished by their multimorbidity status, independence and number of treatments. In addition, we observed a dominant combination of multimorbidity in our sample, combining immune dysfunction and gastrointestinal disorders, neurological and joint diseases. These findings support the hypothesis that an altered gut-brain relationship is involved in the risk of autism spectrum disorder, its outcome, and its association with chronic health conditions. Although larger studies are needed, our results suggest that subgroups of autism spectrum disorder + intellectual disability individuals can be identified based on their multimorbidity and potentially different ageing trajectories. A more comprehensive and personalized approach is needed to reduce the burden of multimorbidity and increase the quality of life and life expectancy in autism spectrum disorder/ intellectual disability.

Globally elevated excitation-inhibition ratio in children with autism spectrum disorder and below-average intelligence

Background

Altered neuronal excitation–inhibition (E–I) balance is strongly implicated in ASD. However, it is not known whether the direction and degree of changes in the E–I ratio in individuals with ASD correlates with intellectual disability often associated with this developmental disorder. The spectral slope of the aperiodic 1/f activity reflects the E–I balance at the scale of large neuronal populations and may uncover its putative alternations in individuals with ASD with and without intellectual disability.

Methods

Herein, we used magnetoencephalography (MEG) to test whether the 1/f slope would differentiate ASD children with average and below–average (< 85) IQ. MEG was recorded at rest with eyes open/closed in 49 boys with ASD aged 6–15 years with IQ ranging from 54 to 128, and in 49 age-matched typically developing (TD) boys. The cortical source activity was estimated using the beamformer approach and individual brain models. We then extracted the 1/f slope by fitting a linear function to the log–log-scale power spectra in the high-frequency range.

Results

The global 1/f slope averaged over all cortical sources demonstrated high rank-order stability between the two conditions. Consistent with previous research, it was steeper in the eyes-closed than in the eyes-open condition and flattened with age. Regardless of condition, children with ASD and below-average IQ had flatter slopes than either TD or ASD children with average or above-average IQ. These group differences could not be explained by differences in signal-to-noise ratio or periodic (alpha and beta) activity.

Limitations

Further research is needed to find out whether the observed changes in E–I ratios are characteristic of children with below-average IQ of other diagnostic groups.

Conclusions

The atypically flattened spectral slope of aperiodic activity in children with ASD and below-average IQ suggests a shift of the global E–I balance toward hyper-excitation. The spectral slope can provide an accessible noninvasive biomarker of the E–I ratio for making objective judgments about treatment effectiveness in people with ASD and comorbid intellectual disability.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-022-00498-2.

EEG abnormalities and clinical phenotypes in pre-school children with autism spectrum disorder

BACKGROUND

Abnormalities on electroencephalography (EEG) results have been reported in a high percentage of children with Autism Spectrum Disorder (ASD). The purpose of this study was to explore the prevalence of EEG abnormalities in a clinical population of pre-school children with Autism Spectrum Disorder and the differences in terms of the following phenotypic characteristics: adaptive behavior, executive functioning, severity of Autism Spectrum Disorder core symptoms, and comorbidity symptoms.

METHODS

A cross-sectional analysis of 69 children who attended the Autism Spectrum Disorder early diagnosis program with electroencephalography and clinical diagnosis was performed. A battery of questionnaires was also made to parents to evaluate emotions, behavior, and functional skills for daily living.

RESULTS

Out of 69 pre-school children with Autism Spectrum Disorder, twenty nine (42%) had abnormalities in electroencephalography results. The group with abnormal epileptiform electroencephalography exhibited more impairment in executive functioning and social-relationship coexisting symptoms.

CONCLUSIONS

The presence of an abnormal epileptiform electroencephalography in pre-school children with ASD already suggests a worse development in clinical features.

Recurrence rate of the first nonfebrile seizure in children with autism spectrum disorder

OBJECTIVE

Epilepsy prevalence is higher in children with Autism Spectrum Disorder (ASD) and is a contributor to morbidity and mortality. Little is known about the recurrence rate after the first nonfebrile seizure in this population, specifically in regard to seizure type and electroencephalogram (EEG) findings.

METHODS

We reviewed pediatric medical records at our institution between 2006 and 2016 for subjects with ASD who had a first seizure. We then looked for risk of a recurrent non-provoked seizure within the next two years.

RESULTS

Overall, the recurrence rate in this study was 70.9%. This is much higher than the general population. The recurrence rate was higher in patients who had a generalized convulsion compared to those who had a behavioral arrest. When the first seizure was a generalized convulsion, there was an 84% chance of developing a second convulsion, whereas the recurrence rate was 59% for behavioral arrest type seizures (p = 0.002). The odds of having recurrence when the first seizure is a generalized convulsion was 5.36 higher than when it was a behavioral arrest (95% CI 2.14-13.42, p < 0.001). An abnormal EEG was a strong predictor of seizure recurrence in both seizure types. However, even with a normal EEG, generalized convulsions were more likely to recur within 2 years compared to behavioral arrest (OR 6.3, 95% CI 2.1-19).

SIGNIFICANCE

The recurrence rate for nonfebrile seizures in children with ASD is much higher than the general population, especially for generalized convulsions. An abnormal EEG has a strong predictive value for seizure recurrence. However, even when the EEG is normal, the recurrence rate for generalized convulsions is quite high. This is an important finding as epilepsy contributes to morbidity and mortality in this group and may impact clinical decisions about when to start anti-seizure medications.

Molecular Dysregulation in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) comprises a heterogeneous group of neurodevelopmental disorders with a strong heritable genetic component. At present, ASD is diagnosed solely by behavioral criteria. Advances in genomic analysis have contributed to numerous candidate genes for the risk of ASD, where rare mutations and s common variants contribute to its susceptibility. Moreover, studies show rare de novo variants, copy number variation and single nucleotide polymorphisms (SNPs) also impact neurodevelopment signaling. Exploration of rare and common variants involved in common dysregulated pathways can provide new diagnostic and therapeutic strategies for ASD. Contributions of current innovative molecular strategies to understand etiology of ASD will be explored which are focused on whole exome sequencing (WES), whole genome sequencing (WGS), microRNA, long non-coding RNAs and CRISPR/Cas9 models. Some promising areas of pharmacogenomic and endophenotype directed therapies as novel personalized treatment and prevention will be discussed.

Evaluation of the clinical characteristics of children with autism spectrum disorder and epilepsy and the perception of their parents on quality of life

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is among the serious clinical pictures of early childhood, and its main symptoms are qualitative dysfunction in social interactions with impairment of verbal and nonverbal communication and limitations in interests and activities.

METHODS

This study aimed to examine the clinical conditions that mediate this comorbidity, compare parental quality of life in isolated ASD and ASD with epilepsy, demonstrate the relationships between clinical and EEG findings obtained in diagnostic evaluation, and examine the results in light of the literature.

RESULTS

The study sample consisted of 154 ASD patients; 26 were girls (16.9 %) and 128 (83.1 %) were boys. Of the patients with epilepsy, seizures were focal in 14 patients (9.1 %), generalized in 9 patients (5.8 %), and unspecified in 1 patient (0.6 %). Intellectual ability was found to be a significant predictor of epilepsy diagnosis. Mean (SD) total scores in the Quality of Life in Autism Questionnaire were 131.84 (10.68) among mothers of children with ASD-epilepsy and 148.33 (14.03) among mothers of children with ASD alone (P <  .001).

CONCLUSION

Many psychiatric and medical conditions can co-occur with ASD. Determining the prognostic criteria for ASD is of great importance in coordinating lifelong autism rehabilitation. Improving autism-specific symptoms will benefit children with ASD as well as help mitigate parental anxiety.

Genetic testing in patients with nonsyndromic autism spectrum disorder and EEG abnormalities with or without epilepsy: Is exome trio-based testing the best clinical approach?

OBJECTIVES

The association between autism spectrum disorder (ASD) and epilepsy is well-known. Abnormalities on electroencephalography (EEG) studies have been reported in patients with ASD without a history of seizures, and these patients have lower functional scores on adaptive measures than patients with ASD with normal EEG studies. The purpose of the study was to evaluate the genetic test approach in children with ASD and abnormal EEGs.

METHODS

Data were collected from medical records at Cincinnati Children's Hospital Medical Center (CCHMC) of a previously published cohort of patients with well-characterized ASD based on evaluation by Developmental Pediatrics. Patients were subdivided into two groups: ASD without epilepsy, but with abnormal EEG results, and ASD with epilepsy. EEG data were abstracted from reports. In this follow-up study, we analyzed genetic testing data, namely the proportion of this cohort that received genetic testing, and the specific type of genetic testing that was ordered to analyze if there were any differences between groups.

RESULTS

Analysis was performed on 173 patients with ASD. Ninety-five patients had a diagnosis of epilepsy. Seventy-eight patients did not have a diagnosis of epilepsy but did have abnormal EEGs. In both groups, approximately three quarters of all subjects received routine neurodevelopmental genetic testing (77% versus 72% p = 0.15) without significant differences between groups. The ASD + epilepsy group was more likely to receive additional second-tier genetic testing outside of a routine neurodevelopmental workup (35% versus 15% p = 0.007). The ASD + epilepsy group was more likely to receive phenotype specific panels, most often an epilepsy gene panel of less than 250 genes (15% versus 3% p = 0.008). However, the ASD + epilepsy group was less likely to receive a genetic diagnosis from testing than the ASD + abnormal EEG group (9% versus 33%, p = 0.047).

CONCLUSIONS

Patients with ASD along with a formal epilepsy diagnosis received more genetic testing; but had an overall lower diagnostic rate than patients with ASD with abnormal EEGs but without a formal epilepsy diagnosis. Patients in this cohort without a diagnosis of epilepsy were more likely to get broad trio-based exome testing instead of targeted epilepsy gene panel testing. A higher diagnostic rate was found in patients when a broad genetic test strategy was implemented.

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.

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.

Phenotypic characterization of individuals with SYNGAP1 pathogenic variants reveals a potential correlation between posterior dominant rhythm and developmental progression

Background

The SYNGAP1 gene encodes for a small GTPase-regulating protein critical to dendritic spine maturation and synaptic plasticity. Mutations have recently been identified to cause a breadth of neurodevelopmental disorders including autism, intellectual disability, and epilepsy. The purpose of this work is to define the phenotypic spectrum of SYNGAP1 gene mutations and identify potential biomarkers of clinical severity and developmental progression.

Methods

A retrospective clinical data analysis of individuals with SYNGAP1 mutations was conducted. Data included genetic diagnosis, clinical history and examinations, neurophysiologic data, neuroimaging, and serial neurodevelopmental/behavioral assessments. All patients were seen longitudinally within a 6-year period; data analysis was completed on June 30, 2018. Records for all individuals diagnosed with deleterious SYNGAP1 variants (by clinical sequencing or exome sequencing panels) were reviewed.

Results

Fifteen individuals (53% male) with seventeen unique SYNGAP1 mutations are reported. Mean age at genetic diagnosis was 65.9 months (28–174 months). All individuals had epilepsy, with atypical absence seizures being the most common semiology (60%). EEG abnormalities included intermittent rhythmic delta activity (60%), slow or absent posterior dominant rhythm (87%), and epileptiform activity (93%), with generalized discharges being more common than focal. Neuroimaging revealed nonspecific abnormalities (53%). Neurodevelopmental evaluation revealed impairment in all individuals, with gross motor function being the least affected. Autism spectrum disorder was diagnosed in 73% and aggression in 60% of cases. Analysis of biomarkers revealed a trend toward a moderate positive correlation between visual-perceptual/fine motor/adaptive skills and language development, with posterior dominant rhythm on electroencephalogram (EEG), independent of age. No other neurophysiology-development associations or correlations were identified.

Conclusions

A broad spectrum of neurologic and neurodevelopmental features are found with pathogenic variants of SYNGAP1. An abnormal posterior dominant rhythm on EEG correlated with abnormal developmental progression, providing a possible prognostic biomarker.

Electronic supplementary material

The online version of this article (10.1186/s11689-019-9276-y) contains supplementary material, which is available to authorized users.

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.