Neuro-epileptic determinants of autism spectrum disorders in tuberous sclerosis complex

Comorbidities in pediatric epilepsy: beyond "just'' treating the seizures

The goal of this review is to discuss the comorbidities reported in specific epilepsy syndromes to examine possible underlying causes or associations and to present data on current therapies for these conditions. Comorbid conditions including cognitive impairment, neuropsychiatric problems, and social difficulties are common in children with epilepsy, and often more disabling than the seizures themselves. Biological factors associated with a greater risk of comorbidity in epilepsy include younger age at seizure onset, cognitive impairment, temporal or frontal lobe onset, and intractability. Social factors correlating with greater risk include lower socioeconomic status, lower parental education level, and poorer family function. These comorbid conditions not only have a significant impact on the child but also are a source of increased stress and burden for families. Increased awareness and early diagnosis of these conditions may affect therapeutic intervention and long-term outcome as well as assist in better understanding of potential risk factors and biological mechanisms.

Neuropsychological attention deficits in tuberous sclerosis complex (TSC)

Tuberous sclerosis complex (TSC) (OMIM191100) is a genetic disorder with multi-system involvement including neurodevelopmental manifestations. There is great interest in understanding the pathogenetic mechanisms underlying these neurobehavioral and neurocognitive manifestations. However, there are still significant gaps in knowledge about the exact neuropsychiatric phenotypes observed in TSC. Here we report on the first systematic evaluation of neuropsychological attentional skills in a population-derived sample of children and adolescents with TSC. The study showed that, even when age, gender, IQ, and intra-familial clustering were controlled for, the TSC group had significantly lower scores than their unaffected siblings on a range of neuropsychological attentional tasks, and that they had significantly more neuropsychological attention deficits. Eighteen of the 20 children (90%) showed deficits on one or more attentional tasks, with dual task performance most consistently impaired (85%) and visual selective attention a relative strength. Active seizures and anti-epilepsy medication did not influence attentional profiles. Furthermore, parent rating of attention-related behaviors were not able to identify children at risk of neuropsychological deficits. The findings suggest that clinical neuropsychological evaluation of attentional skills should be performed in children and adolescents with TSC even when they have normal global intellectual abilities, no seizures, and no disruptive behaviors. Results suggest that the mechanisms underlying these deficits may include contributions from structural, seizure-related and molecular factors.

Therapeutic targeting of mTOR in tuberous sclerosis

Failure in the regulation of mTOR (mammalian target of rapamycin) appears to be critical to the pathogenesis of the inherited disorder tuberous sclerosis and the related lung disease LAM (lymphangioleiomyomatosis). Both diseases are caused by mutations of TSC1 or TSC2 (TSC is tuberous sclerosis complex) that impair GAP (GTPase-activating protein) activity of the TSC1–TSC2 complex for Rheb, leading to inappropriate activity of signalling downstream of mTORC1 (mTOR complex 1). mTOR inhibitors are already used in a variety of clinical settings including as immunosuppressants, anticancer agents and antiproliferative agents in drug-eluting coronary artery stents. They also represent candidate therapies directed to the underlying molecular pathology in tuberous sclerosis and LAM. Phase I/II clinical trials of the mTORC1 inhibitor rapamycin have demonstrated reduction in size of tuberous-sclerosis- and LAM-associated renal tumours (angiomyolipomas) and some evidence for reversible improvement in lung function in patients with LAM. A case series of tuberous-sclerosis-associated brain tumours were also reported to shrink during rapamycin therapy. An important, although variable, feature of the tuberous sclerosis phenotype is learning difficulty. Recent studies in mouse models carrying heterozygous Tsc2 mutations demonstrated improvement in memory and learning deficits following treatment with rapamycin. These promising pre-clinical and early human trials are being followed by larger-scale randomized control trials of mTOR inhibitors for treatment of renal, lung and brain manifestations of TSC1- and TSC2-associated disease.

Current management of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an important cause of epilepsy, autism, and renal and pulmonary disease in children and adults. The clinical course of TSC and the prognosis and appropriate therapy for TSC patients are often different than that for individuals with epilepsy, renal tumors, or interstitial lung disease from other causes. This article reviews the current therapeutic recommendations for medical and surgical management of neurologic, renal, and pulmonary manifestations of TSC. In addition, recent clinical trials using inhibitors of the mammalian target of rapamycin (mTOR) have demonstrated regression of astrocytomas, angiofibromas, and angiomyoliomas, as well as improved pulmonary function in persons with TSC.

Behavior problems in children with tuberous sclerosis complex and parental stress

Behavioral problems are common in children with tuberous sclerosis complex (TSC) and can be challenging to manage at home. Standardized measures were used to assess behavior in 99 pediatric patients with TSC and to evaluate parenting stress in their parents. About 40% of the pediatric patients presented clinically significant behavioral problems, most frequently involving symptoms of autism spectrum disorder, inattention, and hyperactivity. Higher seizure frequency, mixed seizure disorder, and low intellectual functioning placed the patient at significant risk for behavior problems. Almost 50% of participating parents reported experiencing clinically significant parenting stress, which was associated with specific characteristics of the child, including the presence of current seizures, a history of psychiatric diagnosis, low intelligence, and behavioral problems. Clinicians should be aware that behavioral problems are prominent in children with TSC. Referrals for behavioral intervention and monitoring of parental stress should be included in the medical management of children with TSC.

Heterogeneous dysregulation of microRNAs across the autism spectrum

microRNAs (miRNAs) are approximately 21 nt transcripts capable of regulating the expression of many mRNAs and are abundant in the brain. miRNAs have a role in several complex diseases including cancer as well as some neurological diseases such as Tourette's syndrome and Fragile x syndrome. As a genetically complex disease, dysregulation of miRNA expression might be a feature of autism spectrum disorders (ASDs). Using multiplex quantitative polymerase chain reaction (PCR), we compared the expression of 466 human miRNAs from postmortem cerebellar cortex tissue of individuals with ASD (n = 13) and a control set of non-autistic cerebellar samples (n = 13). While most miRNAs levels showed little variation across all samples suggesting that autism does not induce global dysfunction of miRNA expression, some miRNAs among the autistic samples were expressed at significantly different levels compared to the mean control value. Twenty-eight miRNAs were expressed at significantly different levels compared to the non-autism control set in at least one of the autism samples. To validate the finding, we reversed the analysis and compared each non-autism control to a single mean value for each miRNA across all autism cases. In this analysis, the number of dysregulated miRNAs fell from 28 to 9 miRNAs. Among the predicted targets of dysregulated miRNAs are genes that are known genetic causes of autism such Neurexin and SHANK3. This study finds that altered miRNA expression levels are observed in postmortem cerebellar cortex from autism patients, a finding which suggests that dysregulation of miRNAs may contribute to autism spectrum phenotype.

Characterization of autism in young children with tuberous sclerosis complex

Both cognitive impairment and autism are common in the tuberous sclerosis complex, but the relationship between the 2 diagnoses has not been formally explored. The authors evaluated 20 clinic-referred children with tuberous sclerosis complex at ages 18, 24, 36, and 60 months and classified them as autism, autism spectrum disorder, or normal on the basis of the Autism Diagnostic Observation Schedule. Using the Mullen Scale of Early Learning, cognitive function in each subgroup was assessed. The authors then analyzed the subscores of the Autism Diagnostic Observation Schedule in children with autism. Children with autism showed significantly more global cognitive impairment than those without autism. In addition, all children had some baseline cognitive impairment and the majority had deficits in play scores. The authors conclude that clinic-referred children with tuberous sclerosis complex and autism are at considerable risk for cognitive impairment. These characteristics may help to guide more tailored services for these high-risk children.

Neuroimaging correlation with neurological severity in tuberous sclerosis complex

OBJECTIVE

To delineate the relationship between neurological severity and neuroimage of lesion load including specific topography of supratentorial cortical tubers and white matter lesions in tuberous sclerosis complex (TSC).

METHODS

Twenty-five TSC patients more than 2 years of age who underwent conventional and fluid-attenuated inversion recovery sequence (FLAIR) magnetic resonance imaging (MRI) were retrospectively studied. Neurological severity score was designated for three items: seizure, developmental delay and/or mental retardation, and autism. A neuroimaging scoring system was designed to evaluate the load of the cerebrum lesions with respect to location and size of cortical tubers and white matter lesions based on FLAIR MRI.

RESULTS

A linear trend was observed between MRI lesion score and neurological severity score (r=0.511; p=0.009). The lesion score in the left temporal lobe has positive correlation to neurological severity score (r=0.609; p=0.001).

CONCLUSIONS

The brain lesion load was positively correlated with neurological prognosis in TSC patients. Patients with larger lesion load in the left temporal lobe may be correlated with increased neurological severity in right-handed patients with TSC.

The neurobiology of autism

Improving clinical tests are allowing us to more precisely classify autism spectrum disorders and diagnose them at earlier ages. This raises the possibility of earlier and potentially more effective therapeutic interventions. To fully capitalize on this opportunity, however, will require better understanding of the neurobiological changes underlying this devastating group of developmental disorders. It is becoming clear that the normal trajectory of neurodevelopment is altered in autism, with aberrations in brain growth, neuronal patterning and cortical connectivity. Changes to the structure and function of synapses and dendrites have also been strongly implicated in the pathology of autism by morphological, genetic and animal modeling studies. Finally, environmental factors are likely to interact with the underlying genetic profile, and foster the clinical heterogeneity seen in autism spectrum disorders. In this review we attempt to link the molecular pathways altered in autism to the neurodevelopmental and clinical changes that characterize the disease. We focus on signaling molecules such as neurotrophin, Reelin, PTEN and hepatocyte growth factor, neurotransmitters such as serotonin and glutamate, and synaptic proteins such as neurexin, SHANK and neuroligin. We also discuss evidence implicating oxidative stress, neuroglial activation and neuroimmunity in autism.

Effects of rapamycin on gene expression, morphology, and electrophysiological properties of rat hippocampal neurons

PURPOSE

We assayed the effects of rapamycin, an immunomodulatory agent known to inhibit the activity of the mammalian target of rapamycin (mTOR) cascade, on candidate gene expression and single unit firing properties in cultured rat hippocampal neurons as a strategy to define the effects of rapamycin on neuronal gene transcription and excitability.

METHODS

Rapamycin was added (100nM) to cultured hippocampal neurons on days 3 and 14. Neuronal somatic size and dendritic length were assayed by immunohistochemistry and digital imaging. Radiolabeled mRNA was amplified from single hippocampal pyramidal neurons and used to probe cDNA arrays containing over 100 distinct candidate genes including cytoskeletal element, growth factor, transcription factor, neurotransmitter, and ion channel genes. In addition, the effects of rapamycin (200nM) on spontaneous neuronal activity and voltage-dependent currents were assessed.

RESULTS

There were no effects of rapamycin on cell size or dendrite length. Rapamycin altered expression of distinct mRNAs in each gene family on days 3 and 14 in culture. Single unit recordings from neurons exposed to rapamycin exhibited no change from baseline. When spontaneous activity was increased by blocking GABA-mediated inhibition with bicuculline, a fraction of the neurons exhibited a decreased duration of spontaneous bursts and a decrease in synaptic inputs. Rapamycin did not appear to alter voltage-dependent Na(+) or K(+) currents underlying action potentials.

CONCLUSIONS

These data demonstrate that rapamycin does not produce neurotoxicity nor alter dendritic growth and complexity in vitro and does not significantly alter voltage-gated sodium and potassium currents. Rapamycin does affect neuronal gene transcription in vitro. Use of rapamycin in clinical trials for patients with tuberous sclerosis complex warrants vigilance for possible effects on seizure frequency and neurocognitive function.

10-year research update review: psychiatric problems in children with epilepsy

OBJECTIVE

To critically review literature published from 1996 to 2007 on psychopathology in children with epilepsy (CWE).

METHOD

Using Ovid, we searched Medline and PsychInfo databases for original studies on epidemiology, risk factors, clinical characteristics, treatment, and outcome of psychopathology in CWE, ages 0 to 18 years, using the terms "psychopathology," "emotional and behavioral problems," and "mental health problems." We selectively present the findings of studies that are clinically relevant to mental health professionals.

RESULTS

Psychopathology occurs in 37% to 77% of CWE, and attention, internalizing, and thought problems may be specific to epilepsy. Cognitive and linguistic deficits, as well as family factors, have moderating effects on psychopathology in CWE. The association of epilepsy-related variables, including antiepileptic drugs, with psychopathology is inconsistent in cognitively normal CWE. Children with symptomatic epilepsy and devastating epilepsy syndromes have high rates of global developmental delay, hyperactivity, and autistic symptoms. The treatment of psychopathology in CWE integrates standard psychiatric practices.

CONCLUSIONS

Epilepsy is a neuropsychiatric disorder characterized by seizures, psychopathology, cognitive, and linguistic problems. Improved early identification of CWE at risk for psychopathology, evidence-based psychiatric treatment, and multidisciplinary management strategies would advance clinical practice in this highly complex field of pediatric neuropsychiatry.

Biological markers of intellectual disability in tuberous sclerosis

BACKGROUND

Intellectual disability (ID) is highly prevalent in tuberous sclerosis (TS). Putative neurobiological risk factors include indices of cortical tuber (CT) load and epilepsy. We have used univariate and multivariate analyses, including both CT and epilepsy measures as predictors, in an attempt to clarify the pattern of cross-sectional associations between these variables and ID in TS.

METHOD

Forty-eight children, adolescents and young adults with TS were identified through regional specialist clinics. All subjects underwent thorough history taking and examination, and had brain magnetic resonance imaging (MRI) scans. The number and regional distribution of CTs was recorded. Subjects were assigned to one of nine ordered intellectual quotient (IQ) categories (range 130) using age-appropriate tests of intelligence.

RESULTS

On univariate analyses, ID was significantly associated with both a history of infantile spasm (IS) (Z=-2.49, p=0.01) and total CT count (Spearman's rho=-0.30, p=0.04). When controlling for total CT count, the presence of CTs in frontal (regression coefficient=-2.43, p=0.02) and temporal (regression coefficient=-1.60, p=0.02) lobes was significantly associated with ID. In multivariate analyses the association between IS and ID was rendered insignificant by the inclusion of the presence of CTs in temporal and frontal lobes, both of which remained associated (p=0.05 and p=0.06 respectively) with ID.

CONCLUSIONS

The presence of CTs in specific brain regions as opposed to a history of IS was associated with ID in TS. The significance of these findings is discussed in relation to previous work in TS, and the neural basis of intelligence.

EEG abnormalities in West syndrome: correlation with the emergence of autistic features

Autism may develop in children with West syndrome. This study was conducted to determine if EEG abnormalities in patients with West syndrome predict the later onset of autism. Two groups of patients with West syndrome, older than 6 years of age, were studied. One group consisted of those with a past history of West syndrome plus autism (N=14); the control group consisted of those with a past history of West syndrome but without autism (N=14). Patients were followed at regular intervals and video-EEG recordings were done. A total of 108 (autistic group) and 123 (non-autistic group) video-EEGs were examined. The two groups were compared with respect to age, presence or absence of hypsarrhythmia, and characteristics and localization of the epileptogenic foci. chi2 and Fisher's exact tests were used. The number of patients with at least one hypsarrhythmic EEG at the age of one year or later was significantly higher in autistic subjects (86%) than in non-autistic controls (29%). The incidence of EEGs with hypsarrhythmia was also higher in the autistic group, especially in older children (autistic, 49% versus non-autistic, 18% at age 3 years and later). Frontal predominance of the primary foci on EEGs with or without hypsarrhythmia was seen in 95.3% of the autistic group and 28.8% of the non-autistic group (p=0.001). Frontal abnormalities on the EEGs, which were mainly bilateral, and the persistence of hypsarrhythmia were significantly related to the emergence of autistic behavior in patients with West syndrome. These findings suggest that paroxysmal discharges in the cortical areas undergoing rapid maturation may be involved in the development of autistic features.

Childhood autism and associated comorbidities

Autism is a heterogeneous neurodevelopmental disorder with a variety of different etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of autism is still unclear. This review refers to all the genetic syndromes that have been described in children with pervasive developmental disorders (tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Gilles de la Tourette, Williams, etc.). Issues covered include prevalence and main characteristics of each syndrome, as well as the possible base of its association with autism in terms of contribution to the current knowledge on the etiology and genetic base of pervasive developmental disorders.

The development of intellectual abilities in pediatric temporal lobe epilepsy

PURPOSE

The aim of this study was to examine the impact of clinical variables, particularly age at onset of epilepsy, on intellectual function in a group of children with temporal lobe epilepsy (TLE).

METHODS

We reviewed the preoperative neuropsychological test results of 79 children with unilateral TLE who subsequently underwent surgical resection. The impact of age at onset and duration of epilepsy, pathology type, and side of resection on full-scale intelligence quotient (IQ) scores was examined.

RESULTS

Intellectual dysfunction (defined as IQ < 79) was present in 57% of children, and age at onset of epilepsy was the best predictor of intellectual function. Children with epilepsy onset in the first year of life had a particularly high incidence of intellectual impairment (82.4%).

CONCLUSION

These data suggest a critical period during the first year of life for the subsequent development of intellectual abilities and highlight the importance of early treatment in this population.

Tuberous sclerosis complex and epilepsy: recent developments and future challenges

Tuberous sclerosis complex (TSC) is a congenital syndrome characterized by the widespread development of benign tumors in multiple organs, caused by mutations in one of the tumor suppressor genes, TSC1 or TSC2. About 80% of affected patients have a new mutation, and the remaining 20% have inherited a TSC gene mutation from a parent. The disorder affects approximately 1 in 6000 individuals. Cortical tubers are the neuropathological hallmark of TSC. The most common neurological manifestations of TSC are epilepsy, mental retardation, and autistic behavior. Epilepsy occurs in up to 80-90% of patients and is often intractable, with a poor response to anticonvulsant medications. While the molecular basis of TSC is well established, far less is known about the mechanisms of epilepsy in this disorder. In this article, we first summarize known clinical aspects of TSC with emphasis on its neurological features. Then, based on the molecular, pathological, immunohistochemical, neurochemical, and physiological properties of tubers in patients with TSC and in animal models, we discuss possible mechanisms of seizures and epileptogenesis in TSC. Finally, we provide an updated literature review and a consensus statement from the Tuberous Sclerosis Complex Working Group for future research into the mechanisms of epilepsy in TSC.

Etiologies of autism in a case-series from Tanzania

Most autism has a genetic cause although post-encephalitis cases are reported. In a case-series (N = 20) from Tanzania, 14 met research criteria for autism. Three (M:F = 1:2) had normal development to age 22, 35, and 42 months, with onset of autism upon recovery from severe malaria, attended by prolonged high fever, convulsions, and in one case prolonged loss of consciousness. In four other cases (M:F = 3:1), the temporal relationship between onset of autism and severe infection was close, but possibly spurious since malaria is common in Tanzania and there were indications of abnormal development in the child or a family member. In seven cases, (M:F = 6:1) autism onset was unrelated to malaria. The excess of non-verbal cases (N = 10) is related local diagnostic practice.

The psychopathologies of children and adolescents with tuberous sclerosis complex (TSC): a postal survey of UK families

Tuberous Sclerosis Complex (TSC) is a multi-system genetic disorder associated with a wide range of physical features and very high rates of numerous neurocognitive manifestations. However, there is great variability of expression of these features and understanding of the mechanisms underlying this variability is still limited. Mental retardation (MR) and male gender are known to be associated with increased risks of psychopathologies in the general population, but no study has examined these subgroups in TSC as possible contributors to the variable expression observed. It has also remained unclear whether familial-sporadic differences may contribute to variable expression. In this postal survey, UK families reported the frequency and range of physical and behavioural abnormalities in 265 children and adolescents with TSC. Analysis revealed no gender or familial-sporadic differences. Children with MR were significantly more likely to have an autism spectrum disorder, attention deficit-related symptoms and speech and language difficulties. They were more likely to have a history of epilepsy, facial angiofibromata and shagreen patches and tended to have a greater number of physical features of the disorder. However, about one third of the children without MR had features suggestive of a developmental disorder. Anxiety symptoms, depressed mood and aggressive outbursts occurred at equally high rates in those with and without MR. These findings show that TSC can place any child or adolescent at significantly increased risk of a range of neurodevelopmental disabilities. These difficulties, often not recognised, require significant clinical and research attention.

Epilepsy in autism spectrum disorders

Epilepsy is quite common in autism spectrum disorders, and it is increasingly recognized as an additional clinical problem that must be dealt with. The rate of comorbidity varies, depending upon the age and type of disorder, and currently the conservative estimate of comorbidity cases is 20-25% of the whole spectrum. Major risk factors for seizure occurrence are mental retardation and additional neurological disorders, as well as some specific associated medical conditions. Autism with regression has been reported in one-third of children with previously normal or nearly normal development. In an unknown proportion of these subjects, epileptic disorders are concomitant, leading to so-called autistic epileptiform regression. Furthermore, epileptiform abnormalities without seizures are frequent in this population and their role in the development of the nuclear disturbances of autism is controversial. The therapeutic approaches to epilepsy in autism are conventional treatments, yet when seizures are not evident, there is still controversy. Anticonvulsant medications could also potentially interfere with mood and behavioral disturbances frequently observed in ASD. The current understanding of the association between epilepsy and autism is still limited, but from a clinical point of view this association should not be overlooked, and it should be routinely investigated.

The genetics of autistic disorders and its clinical relevance: a review of the literature

Twin and family studies in autistic disorders (AD) have elucidated a high heritability of the narrow and broad phenotype of AD. In this review on the genetics of AD, we will initially delineate the phenotype of AD and discuss aspects of differential diagnosis, which are particularly relevant with regard to the genetics of autism. Cytogenetic and molecular genetic studies will be presented in detail, and the possibly involved aetiopathological pathways will be described. Implications of the different genetic findings for genetic counselling will be mentioned.

Autistic Spectrum Disorder: Evaluating a Possible Contributing or Causal Role of Epilepsy

The onset of epilepsy in brain systems involved in social communication and/or recognition of emotions can occasionally be the cause of autistic symptoms or may aggravate preexisting autistic symptoms. Knowing that cognitive and/or behavioral abnormalities can be the presenting and sometimes the only symptom of an epileptic disorder or can even be caused by paroxysmal EEG abnormalities without recognized seizures, the possibility that this may apply to autism has given rise to much debate. Epilepsy and/or epileptic EEG abnormalities are frequently associated with autistic disorders in children but this does not necessarily imply that they are the cause; great caution needs to be exercised before drawing any such conclusions. So far, there is no evidence that typical autism can be attributed to an epileptic disorder, even in those children with a history of regression after normal early development. Nevertheless, there are several early epilepsies (late infantile spasms, partial complex epilepsies, epilepsies with CSWS, early forms of Landau-Kleffner syndrome) and with different etiologies (tuberous sclerosis is an important model of these situations) in which a direct relationship between epilepsy and some features of autism may be suspected. In young children who primarily have language regression (and who may have autistic features) without evident cause, and in whom paroxysmal focal EEG abnormalities are also found, the possible direct role of epilepsy can only be evaluated in longitudinal studies.

Cognitive and Behavioral Outcomes of Epileptic Syndromes: Implications for Education and Clinical Practice

The educational and social progress of a child with epilepsy depends not only on seizure control but also on cognitive and behavioral factors. The various epilepsy syndromes of childhood and adolescence differ greatly in terms of cognitive and behavioral outcome. A high proportion of babies who have West syndrome and children who have Dravet syndrome (severe myoclonic epilepsy in infancy) will have long-term cognitive and behavioral problems. The Lennox-Gastaut syndrome also often has a poor prognosis in this regard. Children with the Landau-Kleffner syndrome have a variable prognosis, some regain speech and others have permanent speech impairment. Benign childhood epilepsy with centrotemporal spikes is now recognised as lying on a spectrum with the Landau-Kleffner syndrome: mild cases have few if any cognitive or behavioral problems but others may have quite severe difficulties. People with juvenile myoclonic epilepsy may have characteristics suggesting frontal lobe impairment. The educational and social impairments associated with the epilepsy syndromes of childhood and adolescence are of major importance but they have been the subject of remarkably few well-performed studies. The impairments are not always necessarily permanent and it seems highly likely that the cognitive and behavioural outcome of at least some of these syndromes can be influenced greatly by early effective treatment with either antiepileptic medication or surgery.

Medical investigation of children with autistic spectrum disorders

Few well-constructed studies have systematically evaluated medical investigation protocols for children with autistic spectrum disorders. This is in large part due to the heterogeneous nature of the population and changing diagnostic frameworks. This review outlines the studies that have directed investigation strategies to date, and discusses how these might be applied in the clinical situation. The importance of listing the conditions that may be present on the basis of the specific clinical presentation, and using a thorough history and examination to generate a pre-test probability of the target disorders is emphasized if tests are to be useful in directing therapy or broader management approaches.

Tuberous sclerosis complex: a review of the management of epilepsy with emphasis on surgical aspects

OBJECTIVE

To review the management of epilepsy in patients with tuberous sclerosis complex (TSC) with an emphasis on surgical aspects, neuropathology, and pathogenesis.

METHODS

Review of the literature and presentation of the authors' experience of surgery for refractory epilepsy in patients with TSC.

RESULTS

TSC is a multisystem genetic disorder with variable phenotypic expression. TSC results from a mutation in the TSC1 gene on chromosome 9, which codes for hamartin, or in the TSC 2 gene on chromosome 16 which codes for tuberin. The majority of the patients have TSC as a result of spontaneous genetic mutations while in one-third of the patients, the disorder is inherited in an autosomal dominant manner. Epilepsy is the most common neurological complication, and up to 80-90% of individuals with TSC develop epilepsy at some point in their lifetime. The onset of epilepsy is typically in early childhood. Infantile spasms are a very common early seizure type although partial seizures may occur. Developmental delay, intellectual impairment, autism, behavioral problems, and neuropsychiatric disorders occur commonly in individuals with TSC and may be associated with poorly controlled epilepsy. Antiepileptic drugs are the first-line management for epilepsy but the ketogenic diet, resection of one or more tubers, corpus callosotomy, and vagus nerve stimulation are other therapeutic options for individuals with poorly controlled epilepsy.

Tuberous sclerosis

Tuberous sclerosis is a serious inherited disease which poses major challenges for affected families and those caring for them. Identification of the genes causing the condition and study of their protein products has shed light on the pathogenesis of the disease and provided valuable new information about signalling pathways regulating protein synthesis and cell growth. There is now the exciting possibility of drug therapy for some of the manifestations of the disease.

Brief Report: S6 Ribosomal Protein Phosphorylation in Autistic Frontal Cortex and Cerebellum: a Tissue Array Analysis

Few autistic brain samples are available for study, limiting investigations into molecular and histopathological abnormalities associated with this common disease. To facilitate distribution of samples, we have constructed a tissue array containing cerebral and cerebellar cores from 5 autistic children, 1 girl with Rett syndrome, and 5 age-matched controls. To demonstrate the utility of this resource, we examined phosphorylation of the S6 ribosomal protein, a signaling event regulated by the genes mutated in tuberous sclerosis and Cowden disease. We hypothesized that the molecular pathways altered in these inherited conditions associated with autism might be dysregulated in sporadic autistic cases as well. However, no consistent alterations in S6 phosphorylation were detected in autistic tissues compared to controls in the brain regions analyzed.

The management of ADHD and associated problems in a young person with cleidocranial dysostosis (CCD) and mild intellectual disability

It is increasingly recognized that comorbidity is common in all fields of psychiatry, and furthermore, it is acknowledged that a large number of individuals with genetically determined conditions have associated behavioural phenotypes, and are more susceptible to particular psychiatric and psychological comorbidities than others. It is also recognized that the identification of such phenotypes enables clinicians to be more aware of the potential difficulties an individual may experience, and hence, facilitate early diagnosis, effective management and prevention, appropriate allocation of resources and psychoeducation for the individual and their family. We describe the case report of a girl with cleidocranial dysostosis (CCD), and comorbid intellectual disability and attention deficit hyperactivity disorder (ADHD), and suggest the possible existence of a behavioural phenotype. We also highlight the lack of an evidence base for the management of ADHD within the learning-disability population, and describe successful management utilizing the current evidence base, which exists for those of average intellectual ability.

Neuroanatomical correlates of memory deficits in tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a multisystem syndrome classically associated with the occurrence of focal brain dysplasias. We used structural magnetic resonance imaging to test for neuroradiological abnormalities in TSC (tubers, white matter lesions, and subependymal nodules) and to explore the relationships between these lesions and computational morphometric abnormalities of gray and white matter distribution. We tested memory function in TSC and investigated the relationship between memory function and both morphometric variation and lesion load. Patients demonstrated deficits bilaterally in volume of subcortical gray matter regions including thalamus, basal ganglia, insula, and cerebellum, as well as white matter deficits bilaterally in intrahemispheric tracts. Morphometric deficits could not be explained as local effects of lesions. Patients demonstrated deficits in executive working memory and recall memory, sparing recognition. Structure-function mapping showed long-term and working memory function was positively correlated with gray matter density (in thalamus, caudate nucleus, and frontal cortex) but not with lesion load. The neuroanatomical endophenotype of TSC is more extensive than previously recognized and comprises abnormalities in the distribution of gray and white matter in addition to classical lesions. Normal intelligence quotient patients with TSC show a profile of long-term and working memory impairment that is related to gray matter deficits in thalamus and basal ganglia components of fronto-striatal circuits.

Study of the relationship between tuberous sclerosis complex and autistic disorder

There has been increasing awareness that there are behavioral phenotypes in tuberous sclerosis complex with neuropsychiatric symptom complex such as autistic disorder and attention-deficit hyperactivity disorder (ADHD). However, the neurobiologic basis of autistic disorder in tuberous sclerosis complex is still unknown. We studied two cohorts of children followed up since 1986 until 2003, one cohort with tuberous sclerosis complex and another cohort with autistic disorder, to determine the incidence of autistic disorder in tuberous sclerosis complex and the incidence of tuberous sclerosis complex in autistic disorder respectively. We established a Tuberous Sclerosis Complex Registry in 1985 at the University of Hong Kong. In 2004, 44 index cases (the male to female ratio was 0.75:1) were registered. Three had a positive family history of tuberous sclerosis complex. Thus, the total number of tuberous sclerosis complex cases was 47. We adopted the diagnostic criteria of tuberous sclerosis complex for case ascertainment. The period prevalence rate of tuberous sclerosis complex for children and adolescents aged < 20 years is 3.5 per 10,000 (on Hong Kong island, excluding the eastern region with 125,100 aged < 20 years in 2003). Of 44 cases with tuberous sclerosis complex, 7 had autistic disorder. Thus, the incidence of autistic disorder in tuberous sclerosis complex is 16%. During the 17-year period (1986-2003), we collected a database of 753 children (668 boys and 84 girls; male to female ratio 8:1) with autistic disorder and pervasive developmental disorders. For all children with autistic disorder or pervasive developmental disorders, we routinely examined for any features of tuberous sclerosis complex by looking for neurocutaneous markers such as depigmented spots, which appear in 50% of children with tuberous sclerosis complex by the age of 2 years. For those with infantile spasm or epilepsy, the clinical features of tuberous sclerosis complex were monitored regularly during follow-up. Of these, seven had tuberous sclerosis complex. Thus, the incidence of tuberous sclerosis complex in autistic disorder is 0.9%. All of these children are mentally retarded, with moderate to severe grades in an intellectual assessment conducted by a clinical psychologist. Future studies should be directed toward looking at the various behavioral phenotypes in tuberous sclerosis complex and defining these with standardized criteria to look for any real association with the underlying genetic mutation of TSC1 or TSC2 gene or even the site of tubers in the brain.

The diverse clinical manifestations of tuberous sclerosis complex: a review

Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem neurocutaneous disorder. TSC results in hamartomatous lesions primarily involving the skin, central nervous system, kidneys, eyes, heart, and lungs. The clinical findings and severity of TSC are highly variable. Recent advances in our understanding of the complexities of the TSC1 and TSC2 genes are making genotype-phenotype correlations possible. While managing seizures, cognitive dysfunction, and behavioral abnormalities are the primary responsibility of the neurologist, familiarity with all aspects of this disease helps provide better comprehensive care for affected individuals.

The neurobiology of tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a multiorgan genetic disease caused by inactivation of either the TSC1 or TSC2 genes. The disorder typically has profound neurologic involvement and often presents early in life with epilepsy, developmental delay, mental retardation, and autism. These features are generally accepted to result from structural brain abnormalities that are found in patients with TSC. Although much progress has recently been made in discerning the function(s) of the TSC genes, many questions remain as to the role of these genes in brain development and homeostasis. This review will summarize recent progress and suggest future avenues of basic science research.

Neurocutaneous syndromes and epilepsy-issues in diagnosis and management

Epilepsy may be seen as a feature of many of the neurocutaneous syndromes. The challenge lies within the diagnosis of the specific disorder and ultimately control of the epilepsy. Tuberous sclerosis is the most common of the disorders with a frequency of 4.9/100,000. An autosomal-dominant condition, diagnostic features may be unclear under 2 years of age. Population studies suggest a prevalence of epilepsy of 78%, the majority presenting under the age of 12 months, with a high association between the occurrence of seizures and the presence of learning disability. Although an apparent multifocal disease, surgery may have a role to play where seizures are demonstrated to probably arise from a single tuber. Other less common neurocutaneous syndromes also have a high prevalence of epilepsy in association with cerebral malformations; unilateral or lobar malformations should be referred early for surgical consideration. Neurofibromatosis is the second most common of the disorders but the prevalence of epilepsy in this population is relatively low; in addition, a greater proportion may be easier to treat with medication.

Tuberous sclerosis: a syndrome of incomplete tumor suppression

Tuberous sclerosis (TS) is a congenital neurocutaneous syndrome (or phacomatosis) characterized by widespread development of hamartomas in multiple organs. For affected individuals, neurological and psychiatric complications are the most disabling and lethal features. Although the clinical phenotype of TS is complex, only three lesions characterize the neuropathological features of the disease: cortical tubers, subependymal nodules, and subependymal giant cell astrocytomas. The latter is a benign brain tumor of mixed neuronal and glial origin. Tuberous sclerosis is caused by loss-of-function mutations in one of two genes, TSC1 or TSC2. The normal cellular proteins encoded by these genes, hamartin and tuberin, respectively, form a heterodimer that suppresses cell growth in the central nervous system by dampening the phosphatidylinositol 3–kinase signal transduction pathway. The authors review the clinical and neuropathological features of TS as well as recent research into the molecular biology of this disease. Through this work, investigators are beginning to resolve the paradoxical findings that malignant cancers seldom arise in patients with TS, even though the signaling molecules involved are key mediators of cancer cell growth.

Neurocutaneous syndromes: behavioral features

Neurocutaneous syndromes are disorders characterized by a neurological abnormality and cutaneous manifestations. Three of the more common neurocutaneous syndromes are Sturge-Weber syndrome, tuberous sclerosis, and neurofibromatosis. This review focuses on the cognitive and behavioral features of these syndromes.

Consensus clinical guidelines for the assessment of cognitive and behavioural problems in Tuberous Sclerosis

Tuberous Sclerosis (TSC) is a genetic disorder characterised by abnormal growths in a wide range of organs. In the brain, abnormalities of differentiation, proliferation and migration can produce a range of neuropsychiatric features such as mental retardation, autism and ADHD. Although these manifestations are not diagnostic of the disorder, cognitive and behavioural features are often of greatest concern to families yet limited clinical assessment and interventions are currently offered. A consensus panel at a TSC Brain/Behaviour workshop recommended that the cognitive and behavioural profiles of individuals with TSC should be assessed at regular intervals in a planned fashion in accordance with the difficulties associated with the disorder. Evaluations should include the use of standardised neuropsychological and behavioural tools as appropriate to the age and developmental level of the individual assessed. These cognitive and behavioural profiles should be incorporated in the overall formulation of the needs of the person with TSC to plan educational, social and clinical management strategies. Assessments should be documented so that individual longitudinal progress can be monitored. The paper outlines the problems associated with TSC, the purpose of recommended assessments, developmentally appropriate stages for assessment, and identifies specific areas that should be targeted for assessment.

Aetiology of autism: findings and questions

BACKGROUND

Although there is good evidence that autism is a multifactorial disorder, an adequate understanding of the genetic and non-genetic causes has yet to be achieved.

METHODS

Empirical research findings and conceptual reviews are reviewed with respect to evidence on possible causal influences.

RESULTS

Much the strongest evidence concerns the importance of susceptibility genes, but such genes have yet to be identified. Specific somatic conditions (such as tuberous sclerosis and the fragile X anomaly) account for a small proportion of cases. Over recent decades there has been a major rise in the rate of diagnosed autism. The main explanation for this rise is to be found in better ascertainment and a broadening of the diagnostic concept. Nevertheless, some degree of true rise cannot be firmly excluded. However, the epidemiological evidence on the main hypothesized environmental explanation, namely the measles-mumps-rubella vaccine, is consistently negative.

CONCLUSION

Progress on the elucidation of the causes of autism will be crucially dependent on the combination of epidemiology with more basic science laboratory studies.

Neuroepileptic correlates of autistic symptomatology in tuberous sclerosis

Tuberous sclerosis is a genetic condition that is strongly associated with the development of an autism spectrum disorder. However, there is marked variability in expression, and only a subset of children with tuberous sclerosis develop autism spectrum disorder. Clarification of the mechanisms that underlie the association and variability in expression will potentially throw light on the biological processes involved in the etiology of idiopathic forms of autism spectrum disorder. Current evidence indicates that the likelihood of a child with tuberous sclerosis developing an autism spectrum disorder is greater if the child has a mutation in the TSC2 gene, although autism can and does develop in children with TSC1 mutations. The likelihood is also greater if the child has early-onset infantile spasms that are difficult to control, especially if there is an epileptiform focus in the temporal lobes. The emerging evidence is consistent with the notion that early onset electrophysiological disturbances within the temporal lobes (and perhaps other locations) has a deleterious effect on the development and establishment of key social cognitive representations concerned with processing social information, perhaps especially from faces. However, alternative mechanisms to account for the findings cannot yet be ruled out. Future research will have to employ prospective longitudinal designs and treatment trials to clarify the processes involved.

Cognitive and behavioral correlates of tuberous sclerosis complex

Tuberous sclerosis complex is a multisystem disorder in which neurologic problems cause the greatest disability. High rates of mental retardation and autism spectrum disorders are associated with the diagnosis. Early-onset seizures and increased tuber burden are risk factors for cognitive impairment. Early-onset seizures, particularly infantile spasms, are risk factors for autism. Tubers within the temporal lobe and cerebellum are often mentioned as risk factors for autism, although the findings are inconsistent. Seizure control is important for developmental outcome and quality of life. Early behavioral assessment and therapeutic intervention, as well as seizure control, are the most effective means of promoting neurodevelopmental outcome.

Managing epilepsy in tuberous sclerosis complex

Epilepsy is very common in tuberous sclerosis complex and occurs in 80 to 90% of affected individuals during their lifetime. Onset usually occurs during childhood, and up to one third of children with tuberous sclerosis complex will develop infantile spasms. Although not completely understood, the incidence of epilepsy is thought to relate to the neuropathologic features of the disorder, including cortical tubers and other dysgenetic features. Individuals with tuberous sclerosis complex frequently have epileptiform features to their electroencephalograms. Treatment of epilepsy in tuberous sclerosis complex is similar to epilepsy resulting from other causes and includes anticonvulsant medications, the vagus nerve stimulator, and the ketogenic diet. Vigabatrin has been shown to be particularly effective in treating infantile spasms in the setting of tuberous sclerosis complex. Epilepsy surgery has a very important role in the management of children and adults with pharmacoresistant epilepsy in tuberous sclerosis complex.

Autism and tuberous sclerosis

The co-occurrence of autism spectrum disorder and tuberous sclerosis complex has been recognized for decades. The prevalence of tuberous sclerosis complex in the autism spectrum disorder population is 1 to 4%, whereas features of autism spectrum disorder are present in 25 to 50% of individuals with tuberous sclerosis complex. The underlying reason for this association might be a nonspecific disruption of brain function owing to tuberous sclerosis complex, including tuber location, seizures and their effect on brain development, cognitive impairment, a disturbance in brain development in regions associated with autism spectrum disorder, or, less likely, a linkage between a TSC gene and an autism susceptibility gene. Awareness of the relationship between autism spectrum disorder and tuberous sclerosis complex is important during the evaluation of individuals with either disorder. Better delineation of the association and its causative factors is needed for the development of possible interventions.

Molecular pathogenesis of tuber formation in tuberous sclerosis complex

Tuberous sclerosis complex results from mutations in the TSC1 (hamartin) and TSC2 (tuberin) genes. Tubers are cortical developmental malformations in patients with tuberous sclerosis complex that are associated with intractable epilepsy and are composed of histologically distinct cell types, including giant cells and dysplastic neurons. We recently showed that tubers can be dynamic lesions characterized by populations of cells undergoing proliferation, migration, and death. We demonstrate that there is cell-specific activation of the mammalian target of rapamycin (mTOR)/p70S6 kinase/ribosomal S6 cascade in tubers and that giant cells express activated (phosphorylated) p70S6 kinase and ribosomal S6 protein. These findings support impaired hamartin- and tuberin-mediated mTOR pathway regulation. Tubers likely form by constitutive activation of the mTOR cascade during brain development as a consequence of impaired hamartin or tuberin function.

Standardized whole brain mapping of tubers and subependymal nodules in tuberous sclerosis complex

Tuberous sclerosis complex is associated with radiologically visible abnormalities of brain structure, principally tubers and subependymal nodules. We reviewed the literature on neuroimaging of tubers and subependymal nodules and found qualitative evidence of bilateral, predominantly frontal distribution of tubers and bilateral, predominantly subcortical distribution of subependymal nodules in prior studies of pediatric samples. We studied 25 high-functioning adults with tuberous sclerosis complex and normal IQ, acquiring both dual spin-echo and fluid-attenuated inversion recovery magnetic resonance imaging sequences to optimize radiologic diagnosis of tubers and nodules. Individual lesion maps were then coregistered in a standard stereotactic space to facilitate construction of lesion density maps and estimation of lesion density in cortical and subcortical regions reliably defined by a parcellated template image. We found the highest frequency of tubers in frontal lobes and the highest density of tubers in parietal regions. There was significant regional variation in tuber density but no significant lateralization of frequently bilateral tubers. Nodules were located predominantly in the caudate nucleus and were not significantly lateralized. Tuber and nodule volumes were significantly positively correlated. Tuber volume was larger, on average, in patients with a lifetime history of epilepsy, but there was no correlation between IQ and these measures of lesion load. Contemporary image processing tools can be used to enhance quantitative, whole brain analysis of lesion load in patients with tuberous sclerosis complex.

Mouse models of tuberous sclerosis complex

The most devastating complications of tuberous sclerosis complex affect the central nervous system and include epilepsy, mental retardation, autism, and glial tumors. Mutations in one of two genes, TSC1 and TSC2, result in a similar disease phenotype by disrupting the normal interaction of their protein products, hamartin and tuberin, which form a functional signaling complex. Disruption of these genes in the brain results in abnormal cellular differentiation, migration, and proliferation, giving rise to characteristic brain lesions called cortical tubers. Relevant animal models, including conventional and conditional knockout mice, are valuable tools for studying the normal functions of tuberin and hamartin and how disruption of their expression gives rise to the variety of clinical features that characterize tuberous sclerosis complex. In the future, these animals will be invaluable preclinical models for the development of highly specific and efficacious treatments for children affected with tuberous sclerosis complex.

Behavioral and cognitive aspects of tuberous sclerosis complex

Tuberous sclerosis complex is a multisystem genetic disorder. Of all the possible manifestations of this complex disorder, the cognitive and behavioral problems represent the area of greatest concern to parents and caregivers. This review outlines the current evidence regarding global intellectual abilities, behavioral problems, psychiatric diagnoses, learning disorders, and specific neuropsychologic deficits for which individuals with tuberous sclerosis complex are at particularly increased risk, and outlines approaches to intervention. Approximately half of individuals diagnosed with tuberous sclerosis complex present with global intellectual impairment and developmental psychopathologies. Those with normal intellectual abilities are also at high risk of specific neuropsychologic deficits and behavioral, learning, and other psychiatric disorders. There is no evidence for an inevitable decline in cognition or behavior, and any such changes should be investigated. The evolving neurocognitive literature suggests that frontal brain systems might be most consistently disrupted by tuberous sclerosis complex-related neuropathology, thus leading to abnormalities in regulatory and goal-directed behaviors.