Infantile spasms in children with Down syndrome

Early Response, Long-Term Seizure Outcome, and Very-Low-Dose Adrenocorticotrophic Hormone Therapy for Infantile Epileptic Spasms Syndrome With Down Syndrome

BACKGROUND

Infantile epileptic spasms syndrome (IESS) with Down syndrome has good treatment response and good seizure outcomes with high-dose adrenocorticotrophic hormone (ACTH) therapy. We investigated the early treatment response of epileptic spasms (ES), long-term seizure outcome, and efficacy of very-low-dose ACTH therapy for IESS with Down syndrome.

METHODS

We retrospectively investigated patients with Down syndrome and IESS between April 1983 and January 2023. We defined response to treatment as clinical remission and electrographic resolution of hypsarrhythmia after treatment for more than one month and early treatment as any treatment for ES within three months of initiation of treatment. Long-term seizure outcomes were determined by the presence of any type of seizure within one year of the last visit. We investigated the dosage and efficacy of very-low-dose ACTH therapy.

RESULTS

Thirty patients were enrolled with a median follow-up period of 7.7 years (range: 1.3 to 19.1). The response and relapse rates in the early treatment were 83.3% and 16.0%, respectively. The seizure-free rate of long-term seizure outcomes was 80.0%. Long-term seizure outcomes correlated with early treatment response to ES. The response rate of very-low-dose ACTH therapy was 59.3%. The efficacy of ACTH therapy tended to be dose-dependent (P = 0.055).

CONCLUSIONS

Early treatment response to ES may be useful in predicting long-term seizure outcomes of IESS with Down syndrome. Very-low-dose ACTH therapy was the most effective treatment for ES and could exhibit dose-dependent efficacy. Depending on the IESS etiology, the ACTH dose could be reduced to minimize its side effects.

Mechanisms of infantile epileptic spasms syndrome: What have we learned from animal models?

The devastating developmental and epileptic encephalopathy of infantile epileptic spasms syndrome (IESS) has numerous causes, including, but not limited to, brain injury, metabolic, and genetic conditions. Given the stereotyped electrophysiologic, age-dependent, and clinical findings, there likely exists one or more final common pathways in the development of IESS. The identity of this final common pathway is unknown, but it may represent a novel therapeutic target for infantile spasms. Previous research on IESS has focused largely on identifying the neuroanatomic substrate using specialized neuroimaging techniques and cerebrospinal fluid analysis in human patients. Over the past three decades, several animal models of IESS were created with an aim to interrogate the underlying pathogenesis of IESS, to identify novel therapeutic targets, and to test various treatments. Each of these models have been successful at recapitulating multiple aspects of the human IESS condition. These animal models have implicated several different molecular pathways in the development of infantile spasms. In this review we outline the progress that has been made thus far using these animal models and discuss future directions to help researchers identify novel treatments for drug-resistant IESS.

Children with Down syndrome who experience developmental skill loss, characterization, and phenomenology: A case series

Loss of previously acquired developmental skills in children with Down syndrome (DS) is not a well characterized phenomenon. We identified 20 confirmed cases of childhood-onset skill loss for descriptive analysis. Eligible participants were recruited from a specialty clinic for persons with DS at a large medical center. Age and gender-matched participants also with DS but without skill loss were used as a comparison group. Case and control participants were between 3 and 14 years (mean 7.6 yr) at the time of evaluation. Loss of previously acquired communication, social-communication, and play skills was experienced by all cases, as well as new-onset or intensification of pre-existing maladaptive behaviors. The Aberrant Behavior Checklist (ABC)-community was helpful in distinguishing group differences in maladaptive behavior among cases and controls. All cases met DSMIV criteria for autism. Developmental skill loss associated with autism is an extreme example of within-group phenotypic variability and needs to be the focus of further research.

Increased propensity for infantile spasms and altered neocortical excitation-inhibition balance in a mouse model of down syndrome carrying human chromosome 21

Children with Down syndrome (DS, trisomy of chromosome 21) have an increased risk of infantile spasms (IS). As an epileptic encephalopathy, IS may further impair cognitive function and exacerbate neurodevelopmental delays already present in children with DS. To investigate the pathophysiology of IS in DS, we induced IS-like epileptic spasms in a genetic mouse model of DS that carries human chromosome 21q, TcMAC21, the animal model most closely representing gene dosage imbalance in DS. Repetitive extensor/flexor spasms were induced by the GABA_B receptor agonist γ-butyrolactone (GBL) and occurred predominantly in young TcMAC21 mice (85%) but also in some euploid mice (25%). During GBL application, background electroencephalographic (EEG) amplitude was reduced, and rhythmic, sharp-and-slow wave activity or high-amplitude burst (epileptiform) events emerged in both TcMAC21 and euploid mice. Spasms occurred only during EEG bursts, but not every burst was accompanied by a spasm. Electrophysiological experiments revealed that basic membrane properties (resting membrane potential, input resistance, action-potential threshold and amplitude, rheobase, input-output relationship) of layer V pyramidal neurons were not different between TcMAC21 mice and euploid controls. However, excitatory postsynaptic currents (EPSCs) evoked at various intensities were significantly larger in TcMAC21 mice than euploid controls, while inhibitory postsynaptic currents (IPSCs) were similar between the two groups, resulting in an increased excitation-inhibition (E-I) ratio. These data show that behavioral spasms with epileptic EEG activity can be induced in young TcMAC21 DS mice, providing proof-of-concept evidence for increased IS susceptibility in these DS mice. Our findings also show that basic membrane properties are similar in TcMAC21 and euploid mice, while the neocortical E-I balance is altered to favor increased excitation in TcMAC21 mice, which may predispose to IS generation.

Brain circuit pathology in Down syndrome: from neurons to neural networks

Down syndrome (DS), a genetic pathology caused by triplication of chromosome 21, is characterized by brain hypotrophy and impairment of cognition starting from infancy. While studies in mouse models of DS have elucidated the major neuroanatomical and neurochemical defects of DS, comparatively fewer investigations have focused on the electrophysiology of the DS brain. Electrical activity is at the basis of brain functioning. Therefore, knowledge of the way in which brain circuits operate in DS is fundamental to understand the causes of behavioral impairment and devise targeted interventions. This review summarizes the state of the art regarding the electrical properties of the DS brain, starting from individual neurons and culminating in signal processing in whole neuronal networks. The reported evidence derives from mouse models of DS and from brain tissues and neurons derived from individuals with DS. EEG data recorded in individuals with DS are also provided as a key tool to understand the impact of brain circuit alterations on global brain activity.

Response to treatment and outcomes of infantile spasms in Down syndrome

AIM

To estimate the prevalence, and evaluate presentation, treatment response, treatment side effects, and long-term seizure outcomes in all known cases of children with Down syndrome and infantile spasms on the island of Ireland.

METHOD

This was a 10-year retrospective multicentre review of clinical records and investigations, focusing on treatment response, side effects, and long-term outcomes.

RESULTS

The prevalence of infantile spasms in Down syndrome was 3.0% during the study period. Fifty-four infants were identified with median age of spasm onset at 201 days (interquartile range [IQR] 156-242). Spasm cessation was achieved in 88% (n=46) at a median of 110 days (IQR 5-66). The most common first-line medications were prednisolone (n=20, 37%), vigabatrin (n=18, 33.3%), and sodium valproate (n=9, 16.7%). At follow-up (median age 23.7mo; IQR 13.4-40.6), 25% had ongoing seizures and 85% had developmental concerns. Treatment within 60 days did not correlate with spasm cessation. Seventeen children (31%) experienced medication side effects, with vigabatrin accounting for 52%.

INTERPRETATION

Prednisolone is an effective and well-tolerated medication for treating infantile spasms in Down syndrome. Despite the high percentage of spasm cessation, developmental concerns and ongoing seizures were common.

Treatment outcomes for infantile spasms in Japanese children with Down syndrome

BACKGROUND

The aim of this study was to assess the treatment response to conventional antiepileptic drugs and low-dose adrenocorticotropic hormone therapy for infantile spasms in children with Down syndrome.

METHODS

We retrospectively investigated the response and relapse rates, electroencephalography findings, patient characteristics during drug withdrawal, and developmental outcome in 10 children with Down syndrome treated for infantile spasms in our hospital.

RESULTS

All patients showed cessation of infantile spasms and achieved electroencephalographic normalization. Spasm relapse occurred in one of 10 patients (10%). Antiepileptic drugs have been withdrawn for seven of 10 patients (70%), none of whom have experienced seizure relapse since drug withdrawal. The median developmental quotient (n = 8) was 20.5, which shows that the developmental outcome was unfavorable. Low-dose adrenocorticotropic hormone therapy achieved a low seizure remission rate of 28.6%.

CONCLUSIONS

Elucidation of the optimal treatment for infantile spasms in children with Down syndrome is needed to reduce the duration of infantile spasms and improve the developmental outcome.

Epilepsy in Down Syndrome: A Highly Prevalent Comorbidity

Individuals with Down syndrome (DS) have an increased risk for epilepsy during the whole lifespan, but especially after age 40 years. The increase in the number of individuals with DS living into late middle age due to improved health care is resulting in an increase in epilepsy prevalence in this population. However, these epileptic seizures are probably underdiagnosed and inadequately treated. This late onset epilepsy is linked to the development of symptomatic Alzheimer's disease (AD), which is the main comorbidity in adults with DS with a cumulative incidence of more than 90% of adults by the seventh decade. More than 50% of patients with DS and AD dementia will most likely develop epilepsy, which in this context has a specific clinical presentation in the form of generalized myoclonic epilepsy. This epilepsy, named late onset myoclonic epilepsy (LOMEDS) affects the quality of life, might be associated with worse cognitive and functional outcomes in patients with AD dementia and has an impact on mortality. This review aims to summarize the current knowledge about the clinical and electrophysiological characteristics, diagnosis and treatment of epileptic seizures in the DS population, with a special emphasis on LOMEDS. Raised awareness and a better understanding of epilepsy in DS from families, caregivers and clinicians could enable earlier diagnoses and better treatments for individuals with DS.

Excitatory/Inhibitory Synaptic Ratios in Polymicrogyria and Down Syndrome Help Explain Epileptogenesis in Malformations

BACKGROUND

The ratio between excitatory (glutamatergic) and inhibitory (GABAergic) inputs into maturing individual cortical neurons influences their epileptic potential. Structural factors during development that alter synaptic inputs can be demonstrated neuropathologically. Increased mitochondrial activity identifies neurons with excessive discharge rates.

METHODS

This study focuses on the neuropathological examinaion of surgical resections for epilepsy and at autopsy, in fetuses, infants, and children, using immunocytochemical markers, and electron microscopy in selected cases. Polymicrogyria and Down syndrome are highlighted.

RESULTS

Factors influencing afferent synaptic ratios include the following: (1) synaptic short-circuitry in fused molecular zones of adjacent gyri (polymicrogyria); (2) impaired development of dendritic spines decreasing excitation (Down syndrome); (3) extracellular keratan sulfate proteoglycan binding to somatic membranes but not dendritic spines may be focally diminished (cerebral atrophy, schizencephaly, lissencephaly, polymicrogyria) or augmented, ensheathing individual axons (holoprosencephaly), or acting as a barrier to axonal passage in the U-fiber layer. If keratan is diminished, glutamate receptors on the neuronal soma enable ectopic axosomatic excitatory synapses to form; (4) dysplastic, megalocytic neurons and balloon cells in mammalian target of rapamycin disorders; (5) satellitosis of glial cells displacing axosomatic synapses; (6) peri-neuronal inflammation (tuberous sclerosis) and heat-shock proteins.

CONCLUSIONS

Synaptic ratio of excitatory/inhibitory afferents is a major fundamental basis of epileptogenesis at the neuronal level. Neuropathology can demonstrate subcellular changes that help explain either epilepsy or lack of seizures in immature brains. Synaptic ratios in malformations influence postnatal epileptogenesis. Single neurons can be hypermetabolic and potentially epileptogenic.

Infantile Spasms and Trisomy 21: Unfavorable Outcomes with First-line Vigabatrin Therapy

Introduction:

Among children with infantile spasms (ISs), those with trisomy 21 (T21) and those with normal development at onset and no identifiable etiology (previously referred to as “idiopathic”) are expected to have relatively favorable outcomes. The study objective is to determine if differences exist in treatment response, relapse, and subsequent epilepsy between these two groups when vigabatrin is used as first-line treatment.

Methods:

In this retrospective study, patients were classified into the following groups and clinical features were compared: T21 (n = 24) and IS with normal development at onset and no identified etiology (n = 40; control group).

Results:

There was no significant difference in the age of IS onset, sex distribution, or treatment lag between the groups. The T21 compared to the control group required a higher mean number of anti-seizure therapies (3.6 vs. 1.9, p < 0.001), had more relapses [10 (42%) vs. 4 (10%), p < 0.005)], and had higher risk of subsequent epilepsy [11 (46%) vs. 8 (20%), p < 0.003]. Relapses were often delayed in the T21 group, with a mean of 8 months after IS cessation.

Conclusion:

Our results differ from most studies using steroids as first-line treatment where the groups were shown to have similar treatment response and T21 patients had a low risk of relapse and subsequent epilepsy. Therefore, our results suggest that vigabatrin as first-line treatment in T21 with IS may be less favorable than steroids.

Epileptic Spasms in Patients With Down Syndrome: Experiences From Caregivers

Epileptic spasms are the most common type of seizure in infants with Down syndrome; however, the scope of current literature is largely limited to treatment options. We performed a chart review of patients seen at a Down syndrome specialty clinic to identify potential developmental sequelae of Down syndrome and epileptic spasms. We further interviewed parents of the children with Down syndrome and epileptic spasms to identify areas for improvement in counseling, diagnosis, and follow-up. Persistent developmental delays and autism spectrum disorder were highly prevalent in our patients. Caregivers attributed delays in treatment to insufficient counseling and awareness of epileptic spasms. They also identified inadequate emotional support after the diagnosis of the spasms. When counseling parents of infants with Down syndrome, pediatricians should educate about epileptic spasms. If spasms are diagnosed, providing emotional support with frequent follow-up is important. Furthermore, clinicians should monitor for signs of epilepsy and autism spectrum disorder.

Neurologic complications of Down syndrome: a systematic review

Down syndrome (DS) is one of the most well-recognized genetic disorders. Persons with DS are known to have a variety of co-morbid medical problems, affecting nearly all organ systems. Improved healthcare interventions and research have allowed for increased life span of persons with DS, although disorders of the neurologic system remain underexplored. The purpose of this systematic review is to provide clinically pertinent information on the neurological phenotypes of frequently occurring or clinically relevant conditions. A retrospective review of MEDLINE, Scopus, and Pubmed were used to identify sources among seventeen, clinically relevant, search categories. MeSH terms all contained the phrase "Down Syndrome" in conjunction with the topic of interest. 'Frequently-occurring' was defined as prevalent in more than 10% of persons with DS across their lifespan, whereas 'clinically-relevant' was defined as a disease condition where early diagnosis or intervention can augment the disease course. In total, 4896 sources were identified with 159 sources meeting criteria for inclusion. Seventeen clinical conditions were grouped under the following subjects: hypotonia, intellectual and learning disability, cervical instability, autism spectrum disorder, epilepsy, cerebrovascular disease, Alzheimer's disease and neuropsychiatric disease. The results of this review provide a blueprint for the clinical neurologist taking care of persons with DS across the age spectrum and indicate that there are many underrecognized and misdiagnosed co-occurring conditions in DS, highlighting the need for further research.

Epileptic spasms in individuals with Down syndrome: A review of the current literature

Epilepsy can occur in individuals with Down syndrome (DS), with epileptic spasms representing the most frequent seizure type in this population. Epileptic spasms can have devastating consequences on the development of individuals with the condition. This review sought to explore the lifetime prevalence and underlying mechanism of epileptic spasms in this population. We also aimed to review the response rate to various treatments, the relapse rate, and the development of subsequent epilepsy or autism in this population. A comprehensive literature search was conducted for articles discussing the lifetime prevalence, diagnosis, treatment, outcomes, or underlying etiology of epileptic spasms in animal models or individuals with DS. According to available literature, the global clinic-based lifetime prevalence of epilepsy in individuals with DS ranged from 1.6% to 23.1%, with epileptic spasms representing 6.7%-66.7% of these cases. Response rate to treatment with adrenocorticotropic hormone/corticosteroids was highest (81%) and has the most literature supporting its use, with other regimens, including vigabatrin and other antiepileptic drugs, having lower response rates. Epileptic spasms occur more frequently in children with DS than in the general population, though more studies are needed to determine the true lifetime prevalence of epileptic spasms in this population. Generally, children with DS and epileptic spasms tend to be more responsive to treatment and have better outcomes than children with epileptic spasms of unknown etiology (ie, without DS), in terms of response and relapse rates as well as the development of intractable epilepsy (eg, Lennox-Gastaut syndrome).

Multiorgan involvement and management in children with Down syndrome

AIM

To review multiorgan involvement and management in children with Down syndrome (DS).

METHODS

A literature review of articles from 1980 to 2019 using the MEDLINE interface of PubMed was performed using the following search terms- [Down syndrome] or [Trisomy 21] AND [Cardiology] or [Respiratory] or [neurodevelopment] or [epilepsy] or [musculoskeletal] or [immune system] or [haematological] or [endocrine] or [gastrointestinal] or [ophthalmological] or [Ear Nose Throat] or [dermatology] or [renal].

RESULTS

Congenital heart disease particularly septal defects occur in over 60% of infants with DS and 5%-34% of infants develop persistent pulmonary hypertension of the newborn irrespective of a diagnosis of congenital heart disease. Early recognition and management of aspiration, obstructive sleep apnoea and recurrent lower respiratory tract infections (LRTI) could reduce risk of developing pulmonary hypertension in later childhood. Children with DS have an increased risk of autistic spectrum disorder, attention deficit disorder and epilepsy particularly infantile spasms, which are associated with poor neurodevelopmental outcomes. Congenital anomalies of the gastrointestinal and renal system as well as autoimmune diseases, coeliac disease, arthropathy, thyroid dysfunction fold diabetes mellitus and dermatological conditions are more common. Hearing and visual anomalies are also well recognised association with DS (Table 1).

CONCLUSION

Children with DS are at an increased risk of multiorgan comorbidities. Organ-specific health surveillance may provide holistic care for the children and families with DS throughout childhood.

Modeling epileptic spasms during infancy: Are we heading for the treatment yet?

Infantile spasms (IS or epileptic spasms during infancy) were first described by Dr. William James West (aka West syndrome) in his own son in 1841. While rare by definition (occurring in 1 per 3200-3400 live births), IS represent a major social and treatment burden. The etiology of IS varies - there are many (>200) different known pathologies resulting in IS and still in about one third of cases there is no obvious reason. With the advancement of genetic analysis, role of certain genes (such as ARX or CDKL5 and others) in IS appears to be important. Current treatment strategies with incomplete efficacy and serious potential adverse effects include adrenocorticotropin (ACTH), corticosteroids (prednisone, prednisolone) and vigabatrin, more recently also a combination of hormones and vigabatrin. Second line treatments include pyridoxine (vitamin B6) and ketogenic diet. Additional treatment approaches use rapamycin, cannabidiol, valproic acid and other anti-seizure medications. Efficacy of these second line medications is variable but usually inferior to hormonal treatments and vigabatrin. Thus, new and effective models of this devastating condition are required for the search of additional treatment options as well as for better understanding the mechanisms of IS. Currently, eight models of IS are reviewed along with the ideas and mechanisms behind these models, drugs tested using the models and their efficacy and usefulness. Etiological variety of IS is somewhat reflected in the variety of the models. However, it seems that for finding precise personalized approaches, this variety is necessary as there is no "one-size-fits-all" approach possible for both IS in particular and epilepsy in general.

Treatment of Epilepsy Associated with Common Chromosomal Developmental Diseases

Chromosomal diseases are heterogeneous conditions with complex phenotypes, which include also epileptic seizures. Each chromosomal syndrome has a range of specific characteristics regarding the type of seizures, EEG findings and specific response to antiepileptic drugs, significant in the context of the respective genetic etiology. Therefore, it is very important to know these particularities, in order to avoid an exacerbation of seizures or some side effects. In this paper we will present a review of the epileptic seizures and antiepileptic treatment in some of the most common chromosomal syndromes.

Infantile Spasms: An Update on Pre-Clinical Models and EEG Mechanisms

Infantile spasms (IS) is an epileptic encephalopathy with unique clinical and electrographic features, which affects children in the middle of the first year of life. The pathophysiology of IS remains incompletely understood, despite the heterogeneity of IS etiologies, more than 200 of which are known. In particular, the neurobiological basis of why multiple etiologies converge to a relatively similar clinical presentation has defied explanation. Treatment options for this form of epilepsy, which has been described as “catastrophic” because of the poor cognitive, developmental, and epileptic prognosis, are limited and not fully effective. Until the pathophysiology of IS is better clarified, novel treatments will not be forthcoming, and preclinical (animal) models are essential for advancing this knowledge. Here, we review preclinical IS models, update information regarding already existing models, describe some novel models, and discuss exciting new data that promises to advance understanding of the cellular mechanisms underlying the specific EEG changes seen in IS—interictal hypsarrhythmia and ictal electrodecrement.

Brain MRI abnormalities in patients with infantile spasms and Down syndrome

INTRODUCTION

Infantile spasms (IS) are the most frequent epilepsy syndrome in children with Down syndrome (DS). In DS, cellular (synaptic/dendritic changes) and molecular mechanisms are believed to contribute to epileptogenesis, rather than gross structural anomalies. Neuroimaging is a standard part of the evaluation of newly diagnosed infantile epilepsy including IS and, in this age group, often requires sedation. It is unclear if neuroimaging provides additional clinically useful etiologic information in IS associated with DS.

METHODS

We conducted a retrospective chart review and detailed neuroimaging review in 36 patients (24 males) with IS and DS, cared for at Boston Children's Hospital.

RESULTS

Incidental imaging abnormalities were common (42%), but potentially relevant etiologic abnormalities were rare (16%). Structural congenital or acquired abnormalities were associated with ongoing antiepileptic drug (AED) use (p = 0.02), as well as refractory epilepsy (p = 0.04). However, neuroimaging did not alter the treatment plan for any of these patients.

CONCLUSIONS

Clinicians must carefully weigh the benefits and risks of neuroimaging in infants with DS and IS, as neuroimaging did not lead to any changes in clinical management in our patients but may offer information regarding prognosis.

Infantile Spasms in Children With Down Syndrome: Identification and Treatment Response

Objectives. To evaluate infantile spasms in children with Down syndrome including assessment of efficacy of treatments, presence of treatment lag, and to identify risk factors that may predict the occurrence of infantile spasms in this population. Methods. Medical charts, electroencephalograms, and brain magnetic resonance images were evaluated in 37 children treated for infantile spasms at a single institution from 2005 to 2015. Results. Mean age at diagnosis was 9.16 months, with an average 1.38-month lag from spasms onset to start of medication. Prevalence of heart defects and pulmonary hypertension were significantly higher in those with infantile spams compared with those without. Eighty-one percent receiving adrenocorticotropic hormone as initial treatment experienced remission within 2 weeks, 94.1% had remission at 3 months compared with 18.8% at 2 weeks and 35.3% at 3 months for other first-line treatments. Type of treatment was the only predictor of good outcome. Conclusions. Results stress the importance of early recognition and adrenocorticotropic hormone treatment for this seizure disorder in children with Down syndrome.

Kcnj6(GIRK2) trisomy is not sufficient for conferring the susceptibility to infantile spasms seen in the Ts65Dn mouse model of down syndrome

OBJECTIVE

Infantile spasms (IS) is a catastrophic childhood seizure disorder that is characterized by extensor and/or flexor spasms, cognitive deterioration and a characteristic EEG abnormality. The latter consists of a pattern of a spike-wave followed by an electrodecremental response (EDR), which is a flattening of the EEG waveform amplitude. The mechanism/circuitry that underpins IS is unknown. Children with Down Syndrome (DS) are particularly vulnerable to IS. The standard mouse model of DS is the Ts65Dn mutant mouse (Ts). Using the Ts mouse, we have created an animal model of IS in DS. This model entails the treatment of Ts mice with a GABA_BR agonist with a resultant recapitulation of the semiological, electrographic, and pharmacological phenotype of IS. One of the genes triplicated in Ts mice is the kcnj6 gene which codes for the G-protein inwardly rectifying potassium channel 2 (GIRK2) protein. We have shown that over expression of GIRK2 in Ts brain is necessary for the production of the GABA_BR agonist induced IS phenotype in the Ts mouse. Here, we ask the question whether the excess GIRK2 is sufficient for the production of the GABA_BR agonist induced IS phenotype.

METHODS

To address this question, we used kcnj6 triploid mice, and compared the number of spasms via video analysis and EDR events via EEG to that of the WT mice.

RESULTS

We now show that GABA_RR agonist-treated kcnj6 triploid mice failed to show susceptibility to the IS phenotype. Therefore, over expression of GIRK2 in the brain is necessary, but not sufficient to confer susceptibility to the GABA_BR agonist-induced IS phenotype in the Ts model of DS.

SIGNIFICANCE

It is therefore likely that GIRK2 is working in concert with another factor or factors that are altered in the Ts brain in the production of the GABA_BR agonist-induced IS phenotype.

Infantile spasms in down syndrome: Rescue by knockdown of the GIRK2 channel

OBJECTIVE

The Ts65Dn (Ts) mouse model of Down syndrome (DS) is exquisitely sensitive to an infantile spasms phenotype induced by γ-aminobutyric acidB receptor (GABAB R) agonists. The Ts mouse contains the core genomic triplication of the DS critical region, which includes 3 copies of the Kcnj6 gene that encodes the GABAB R-coupled G protein-coupled inward rectifying potassium channel subunit 2 (GIRK2) channel. We test the hypothesis that GIRK2 is necessary for the GABAB R agonist-induced infantile spasms phenotype in Ts.

METHODS

We assessed the result of either genetic or pharmacological knockdown of the GIRK2 channel in Ts brain upon the GABAB R agonist-induced infantile spasms phenotype in the Ts mouse model of DS. As well, we examined GABAB R currents in hippocampal neurons prepared from GIRK2-trisomic Ts control mice and GIRK2-disomic Ts mice in which Kcnj6 had been genetically knocked down from 3 to 2 copies.

RESULTS

The reduction of the copy number of Kcnj6 in Ts mice rescued the GABAB R agonist-induced infantile spasms phenotype. There was an increase in GABAB R-mediated GIRK2 currents in GIRK2-trisomic Ts mouse hippocampal neurons, which were normalized in the GIRK2-disomic Ts mice. Similarly, pharmacological knockdown of the GIRK2 channel in Ts brain using the GIRK antagonist tertiapin-Q also rescued the GABAB R agonist-induced infantile spasms phenotype in Ts mutants.

INTERPRETATION

The GABAB R-coupled GIRK2 channel is necessary for the GABAB R agonist-induced infantile spasms phenotype in the Ts mouse and may represent a novel therapeutic target for the treatment of infantile spasms in DS. Ann Neurol 2016;80:511-521.

Evaluation of the Nutritional Status in Institutionalized Children and its Relationship to the Development of Epilepsy

Malnutrition as defined by the World Health Organization (WHO) in 1973 is an association of pathologic conditions caused by a lack of calories or protein intake in variable proportions. It is still one of the leading causes of infant mortality in developing countries. Risk factors for early malnutrition are absence of perinatal care and low birth weight. Epilepsy is also a very prevalent condition in childhood. A relationship between malnutrition and epilepsy has been suggested in many basic studies but it has never been proven in humans. In order to verify if malnutrition can lead to epilepsy, we reviewed anthropometric and medical files from infants in a governmental institution and tried to relate to an outcome of epilepsy. We defined malnutrition as height/weight below two pattern deviations from the NCHS tables. Two hundred and forty three children were included, 101 with malnutrition and 133 nourished. Our results indicate a predominance of malnutrition in girls (49%) and a comorbidity of malnutrition and neurological disorders. Although there were more cases of epilepsy in the malnourished group, the difference was not significant, and we could not assume that malnutrition was the cause of epilepsy in these cases because of the association of many other diseases that could also damage the central nervous system.

Pediatric Epileptic Encephalopathies: Pathophysiology and Animal Models

Epileptic encephalopathies are syndromes in which seizures or interictal epileptiform activity contribute to or exacerbate brain function, beyond that caused by the underlying pathology. These severe epilepsies begin early in life, are associated with poor lifelong outcome, and are resistant to most treatments. Therefore, they represent an immense challenge for families and the medical care system. Furthermore, the pathogenic mechanisms underlying the epileptic encephalopathies are poorly understood, hampering attempts to devise novel treatments. This article reviews animal models of the three classic epileptic encephalopathies-West syndrome (infantile spasms), Lennox-Gastaut syndrome, and continuous spike waves during sleep or Landau-Kleffner syndrome-with discussion of how animal models are revealing underlying pathophysiological mechanisms that might be amenable to targeted therapy.

Epilepsy in children with Down syndrome: not so benign as generally accepted

Down syndrome (DS) is one of the most common causes of mental retardation in children. Many children with DS suffer from neurologic problems, including seizures. Epileptic spasms (ES) are the most frequently reported seizure type. As in the general epilepsy population, ES are rather difficult to control with anti-epileptic drugs. Different treatment regimens have been proposed in the literature, most of them containing vigabatrin or steroids. We present 12 children with DS, who were seen and treated at the Antwerp University Hospital because of seizures. Eight of them presented with ES. Different treatment regimens were used, with varying outcome. This article summarizes our experience with epilepsy in children with DS, describing the different treatment options that were used. We found a poor outcome in these children, compared to most previous reports. Although steroids play an important role in the treatment of ES worldwide, we found a low success rate (8.3 %) of these drugs.

Cerebal overinhibition could be the basis for the high prevalence of epilepsy in persons with Down syndrome

Down syndrome (DS) is the most common cause of genetic intellectual disability, and the trisomy 21 is associated with more than 80 clinical traits, including higher risk for epilepsy. Several hypotheses have been put forward to explain the mechanisms underlying increased seizure susceptibility in DS: inherent structural brain abnormalities, abnormal cortical lamination, disruption of normal dendritic morphology, and underdeveloped synaptic profiles. A deficiency or loss of GABA inhibition is hypothesized to be one of the main alterations related to the epileptogenic process. Paradoxically, enhanced GABA inhibition has also been reported to promote seizures. One major functional abnormality observed in the brains of individuals and mouse models with DS appears to be an imbalance between excitatory and inhibitory neurotransmission, with excessive inhibitory brain function. This review discusses the GABAergic system in the human DS brain and the possible implication of the GABAergic network circuit in the epileptogenic process in individuals where the pathogenetic basis for epilepsy is unknown.

Autism spectrum disorder and epilepsy: Disorders with a shared biology

There is an increasing recognition of clinical overlap in patients presenting with epilepsy and autism spectrum disorder (ASD), and a great deal of new information regarding the genetic causes of both disorders is available. Several biological pathways appear to be involved in both disease processes, including gene transcription regulation, cellular growth, synaptic channel function, and maintenance of synaptic structure. We review several genetic disorders where ASD and epilepsy frequently co-occur, and we discuss the screening tools available for practicing neurologists and epileptologists to help determine which patients should be referred for formal ASD diagnostic evaluation. Finally, we make recommendations regarding the workflow of genetic diagnostic testing available for children with both ASD and epilepsy. This article is part of a Special Issue entitled "Autism and Epilepsy".

A review of the neurological and neurosurgical implications of Down syndrome in children

Down syndrome is the most commonly encountered chromosomal translation and has been associated with significant congenital abnormalities in various organ systems. Along with classic facial findings, it may involve the gastroenterologic, cardiac, ophthalmologic, endocrine, immunologic, orthopedic, or neurologic systems. With respect to the neurological system, a higher incidence of moyamoya, seizure disorders, strokes, and spinal ligamentous laxity has been described in these children. We have summarized the current available literature with respect to children who have Down syndrome and the varying neurological pathologic entities associated to help health care providers better understand these patients.

Down syndrome and personalized medicine: changing paradigms from genotype to phenotype to treatment

Personalized Medicine represents a paradigm shift in the conceptual framework of research and clinical care. This shift argues that Down syndrome is a treatable condition, and therefore we must invest in research to improve outcomes. Individuals with Down syndrome have varying levels of increased risk for a number of co-morbidities, including infantile spasms and early onset Alzheimer's disease. We will review research in these associated conditions to show how investigators are attempting to identify biomarkers, including genomic, epigenomic, proteomic and metabolomic "signatures" that will predict who may be at risk to develop a specific co-morbidity prior to onset and will provide novel targets for therapeutic development. This Personalized Medicine approach will permit predictive and preventive approaches for individuals at increased risk for co-morbidities. The support for clinical trials among individuals with Down syndrome is beginning to overcome the "culture of intractability" that has surrounded this disorder.

Treatment outcomes of West syndrome in infants with Down syndrome

West syndrome constitutes the most frequent of all seizure types in infants with Down syndrome. We retrospectively reviewed records of 12 infants with Down syndrome and West syndrome, accounting for 5% of 239 infants with West syndrome from a comprehensive epilepsy database during a 17-year period. All demonstrated classic hypsarrhythmia on video electroencephalograms. One had clinically responded to clonazepam, and one was not treated because the parents refused any treatment. Seven of 10 infants demonstrated a complete response to high-dose natural adrenocorticotrophic hormone. Four (57%) of these seven infants relapsed. Relapses occurred as long as 2 years after cessation of the initial presentation of infantile spasms. At most recent follow-up (median age, 5 years), 8/12 (67%) were seizure-free, and seven were off any medications. Two of three nonresponders manifested intractable epilepsy and profound mental retardation. Developmentally, 6/8 who could be assessed met criteria for autistic spectrum disorder. Close follow-up is necessary even after successful initial treatment, because relapses are frequent and can occur as long as 2 years later.

Novel animal models of pediatric epilepsy

When mimicking epileptic processes in a laboratory setting, it is important to understand the differences between experimental models of seizures and epilepsy. Because human epilepsy is defined by the appearance of multiple spontaneous recurrent seizures, the induction of a single acute seizure without recurrence does not constitute an adequate epilepsy model. Animal models of epilepsy might be useful for various tasks. They allow for the investigation of pathophysiological mechanisms of the disease, the evaluation, or the development of new antiepileptic treatments, and the study of the consequences of recurrent seizures and neurological and psychiatric comorbidities. Although clinical relevance is always an issue, the development of models of pediatric epilepsies is particularly challenging due to the existence of several key differences in the dynamics of human and rodent brain maturation. Another important consideration in modeling pediatric epilepsy is that "children are not little adults," and therefore a mere application of models of adult epilepsies to the immature specimens is irrelevant. Herein, we review the models of pediatric epilepsy. First, we illustrate the differences between models of pediatric epilepsy and models of the adulthood consequences of a precipitating insult in early life. Next, we focus on new animal models of specific forms of epilepsies that occur in the developing brain. We conclude by emphasizing the deficiencies in the existing animal models and the need for several new models.

Animal models

Epilepsy accounts for a significant portion of the dis-ease burden worldwide. Research in this field is fundamental and mandatory. Animal models have played, and still play, a substantial role in understanding the patho-physiology and treatment of human epilepsies. A large number and variety of approaches are available, and they have been applied to many animals. In this chapter the in vitro and in vivo animal models are discussed,with major emphasis on the in vivo studies. Models have used phylogenetically different animals - from worms to monkeys. Our attention has been dedicated mainly to rodents.In clinical practice, developmental aspects of epilepsy often differ from those in adults. Animal models have often helped to clarify these differences. In this chapter, developmental aspects have been emphasized.Electrical stimulation and chemical-induced models of seizures have been described first, as they represent the oldest and most common models. Among these models, kindling raised great interest, especially for the study of the epileptogenesis. Acquired focal models mimic seizures and occasionally epilepsies secondary to abnormal cortical development, hypoxia, trauma, and hemorrhage.Better knowledge of epileptic syndromes will help to create new animal models. To date, absence epilepsy is one of the most common and (often) benign forms of epilepsy. There are several models, including acute pharmacological models (PTZ, penicillin, THIP, GBL) and chronic models (GAERS, WAG/Rij). Although atypical absence seizures are less benign, thus needing more investigation, only two models are so far available (AY-9944,MAM-AY). Infantile spasms are an early childhood encephalopathy that is usually associated with a poor out-come. The investigation of this syndrome in animal models is recent and fascinating. Different approaches have been used including genetic (Down syndrome,ARX mutation) and acquired (multiple hit, TTX, CRH,betamethasone-NMDA) models.An entire section has been dedicated to genetic models, from the older models obtained with spontaneous mutations (GEPRs) to the new engineered knockout, knocking, and transgenic models. Some of these models have been created based on recently recognized patho-genesis such as benign familial neonatal epilepsy, early infantile encephalopathy with suppression bursts, severe myoclonic epilepsy of infancy, the tuberous sclerosis model, and the progressive myoclonic epilepsy. The contribution of animal models to epilepsy re-search is unquestionable. The development of further strategies is necessary to find novel strategies to cure epileptic patients, and optimistically to allow scientists first and clinicians subsequently to prevent epilepsy and its consequences.

Genetic and biologic classification of infantile spasms

Infantile spasms constitute an age-dependent epilepsy, highly associated with cognitive impairment, autism, and movement disorders. Previous classification systems focused on a distinction between symptomatic and cryptogenic etiologies, and have not kept pace with recent discoveries of mutations in genes in key pathways of central nervous system development in patients with infantile spasms. Children with certain genetic syndromes are much likelier to manifest infantile spasms, and we review the literature to propose a genetic classification of these disorders. Children demonstrating genetic associations with infantile spasms also manifest phenotypes beyond epilepsy that may be explained by recent advances in the understanding of underlying biological mechanisms. Therefore we propose a biologic classification of genes highly associated with infantile spasms, and articulate models for infantile spasms pathogenesis based on those data. The two best described pathways of pathogenesis involve abnormalities in the gene regulatory network of gamma-aminobutyric acidergic forebrain development and abnormalities in molecules expressed at the synapse. These genetic and biologic classifications are flexible, and they should encourage much needed progress in syndrome recognition, clinical genetic testing, and the development of new therapies targeting specific pathways of pathogenesis.

Cognitive deficits and associated neurological complications in individuals with Down's syndrome

Improvements in medical interventions for people with Down's syndrome have led to a substantial increase in their longevity. Diagnosis and treatment of neurological complications are important in maintaining optimal cognitive functioning. The cognitive phenotype in Down's syndrome is characterised by impairments in morphosyntax, verbal short-term memory, and explicit long-term memory. However, visuospatial short-term memory, associative learning, and implicit long-term memory functions are preserved. Seizures are associated with cognitive decline and seem to cause additional decline in cognitive functioning, particularly in people with Down's syndrome and comorbid disorders such as autism. Vision and hearing disorders as well as hypothyroidism can negatively impact cognitive functioning in people with Down's syndrome. Dementia that resembles Alzheimer's disease is common in adults with Down's syndrome. Early-onset dementia in adults with Down's syndrome does not seem to be associated with atherosclerotic complications.

Infantile spasms: a critical review of emerging animal models

Infantile spasms is a developmental epilepsy syndrome with unique clinical and EEG features, a specific pattern of pharmacological responsiveness, and poor outcome in terms of cognition and epilepsy. Despite the devastating nature of infantile spasms, little is known about its pathogenesis. Until recently, there has been no animal model available to investigate the pathophysiology of the syndrome or to generate and test novel therapies. Now, several promising animal models have emerged, spanning the etiological spectrum from genetic causes (e.g., Down syndrome or Aristaless-related homeobox [ARX] mutation) to acquired causes (e.g., endogenous and exogenous toxins or stress hormones with convulsant activity or blockade of neural activity). These new models are discussed in this review, with emphasis on the insights each can provide for understanding, treating, and preventing infantile spasms.

Infantile spasms and Down syndrome: a new animal model

Infantile spasms is a catastrophic childhood seizure disorder for which few animal models exist. Children with Down syndrome are highly susceptible to infantile spasms. The Ts65Dn mouse is a valid model for Down syndrome; therefore, we tested the hypothesis that the Ts65Dn mouse represents a substrate for an animal model of infantile spasms. The baseline of naïve Ts65Dn mice showed spontaneous spike-and-wave discharges, a pattern that worsened with baclofen and gamma-butyrolactone, which induced acute epileptic extensor spasms (AEES) associated with epileptiform polyspike bursts and an electrodecremental response on the EEG. GABABR-agonist-induced AEES were significantly reduced with vigabatrin, rodent ACTH fragment, valproic acid, ethosuximide, and CGP 35348. Porcine ACTH had no effect. GABABR protein expression was significantly increased in the thalamus and medulla oblongata of Ts65D mice in comparison with wild-type controls. The GABABR agonist-treated Ts65Dn mouse shows the unique clinical, electrographic, and pharmacologic signature of infantile spasms and represents a valid, acute model of this disorder. GABABR-mediated mechanisms may contribute to the increased susceptibility of children with Down syndrome to infantile spasms.

Clinical and EEG features of epilepsy in children and adolescents in Down syndrome

Epilepsy is rarely considered as a major component of Down syndrome. We evaluated the prevalence of epileptic seizures in 252 (97 girls and 155 boys) children and adolescents with Down syndrome evaluated at Department of Pediatric Neurology between 1994 and 2007. Results showed that 15 (6%) patients had epileptic seizures: 8 partial seizures; 1 infantile spasms, 1 Lennox-Gastaut syndrome, and 5 generalized tonic-clonic seizures. Electroencephalography was performed on all patients with Down syndrome. Focal changes, spikes, generalized slowing, and hypsarrhythmia were recorded. The electroencephalography was found to be abnormal in Down syndrome with epilepsy in 100%. Almost 60% of patients with Down syndrome and epilepsy had seizures, but 40% of the patients were seizures-free. Quantitative electroencephalography analysis revealed significant differences between children with Down syndrome and the control groups in the alpha, delta, and beta rhythms. Our findings are in accordance with other reports.

Over-inhibition: a model for developmental intellectual disability

Developmental intellectual disability (DID) is a daunting societal problem. Although tremendous progress has been made in defining the genetic causes of DID, therapeutic strategies remain limited. In particular, there is a marked absence of a unified approach to treating cognitive impairments associated with DID. Here, we suggest that the brain in many DID-related disorders is subject to a basic imbalance in neuronal activity, with an increased contribution of inhibition to neural circuits. This over-inhibition, in turn, is predicted to lead to deficits in synaptic plasticity and learning and memory. We further discuss possibilities for pharmacological intervention in DID, focusing on the concept of drug-induced 'therapeutic neuroadaptation' as a means of stably enhancing constitutive circuit excitability and cognition over time.

Comorbidity, hospitalization, and medication use and their influence on mental and motor development of young infants with Down syndrome

OBJECTIVE

Young infants with Down syndrome have an increased occurrence of several well-known medical conditions such as congenital heart and gastrointestinal disease. The aim of this study was to establish consequences like hospitalization and medication use rates and to determine their possible influence on early neurodevelopment.

PATIENTS AND METHODS

This study compared 2 years of thyroxine treatment with placebo in 196 neonates with Down syndrome who were included in a previously reported randomized clinical trial. Parents were interviewed about comorbidity, hospitalization, and medication use at random assignment and regularly thereafter. Data were cross-checked with discharge letters when available. The influence of comorbidity on neurodevelopment at 2 years old (Bayley Scales of Infant Development II) was determined by stepwise multiple linear-regression analysis.

RESULTS

Before trial entry, 163 infants with Down syndrome had been admitted to hospital for an average of 14.01 days, whereas during the trial, 95 of 181 infants who completed the trial were hospitalized for an average 19.75 days. Main hospitalization reasons during the trial were lung/airway and congenital heart and gastrointestinal disease. The 48 infants operated on for heart or gastrointestinal disease accounted for 1401 of the total number of 1876 hospital admission days during the trial and for 33 of 62 admissions for lung/airway infection. During their second year of life, approximately 60% of the infants were prescribed drugs, mostly antibiotics and pulmonary. Regression analysis showed infantile spasms, "other" central nervous system disease, and gastrointestinal disease necessitating surgery to be associated with greater developmental age delays at 24 months old (mental: 6.87, 3.52, and 1.69 months; and motor: 3.59, 2.54, and 1.68 months, respectively).

CONCLUSIONS

Hospital admission and medication use rates in young infants with Down syndrome are still very high, mainly because of congenital heart and gastrointestinal disease and acquired respiratory disease. Central nervous system disease and gastrointestinal disease necessitating surgery were independently associated with a worse developmental outcome.

Down syndrome, Alzheimer's disease and seizures

Neuropathologically, Alzheimer-type abnormalities are demonstrated in patients with Down syndrome (DS), both demented and nondemented and more than a half of patients with DS above 50 years develop Alzheimer's disease (AD). The apolipoprotein E epsilon4 allele, oestrogen deficiency, high levels of Abeta1-42 peptide, elevated expression of BACE2, and valine polymorphism of prion protein gene are associated with earlier onset of dementia in DS individuals. Advanced AD alone may be an important risk factor for new-onset seizures in older adults and age above 60 years is a recognized risk factor for poor outcome from convulsive and nonconvulsive status epilepticus. DS patients aged over 45 years are significantly more likely to develop Alzheimer's disease than those less than 45 years and up to 84% demented individuals with DS develop seizures. Late-onset epilepsy in DS is associated with AD, while early-onset epilepsy is associated with an absence of dementia. In AD patients with a younger age of dementia onset are particularly susceptible to seizures. DS adults with epilepsy score significantly higher overall on the adaptive behaviour profile. Language function declined significantly more rapidly in AD patients with seizures and there is a good correlation between the severity of EEG abnormalities and cognitive impairment whereas in DS slowing of the dominant occipital rhythm is related to AD and the frequency of the dominant occipital activity decreases at the onset of cognitive deterioration.

L'épilepsie dans les aberrations chromosomiques

Epilepsy is among the most frequent finding in many chromosome aberrations. While most chromosome aberrations can be associated with different seizure types, there are few aberrations which feature specific seizures and EEG patterns. Among the 400 different chromosomal imbalances described with seizures and EEG abnormalities, eight have a high association with epilepsy. These comprise: the monosomy 1p36, Wolf-Hirschhorn syndrome (4p-), Angelman syndrome, Miller-Dieker del 17p13.3, the inversion duplication 15 syndrome, ring 20 and ring 14 syndromes, Down's syndrome. These chromosomal regions where aberrations have an evident association with epilepsy may be useful targets for gene hunters. On the other hand, a better characterisation of epileptic syndrome in these disorders may lead to a better and specific treatment.

Multi-institutional study on the correlation between chromosomal abnormalities and epilepsy

While there is an abundance of literature describing the association of chromosome aberrations with epilepsy, only a few refer to the detailed features of epilepsy. It is important to investigate the associations between specific chromosome abnormalities and features of epilepsy to identify genes involved in epilepsy and treat them more effectively. We investigated the correlation between specific chromosome aberrations and epilepsy by sending questionnaires to the members of Kyoto Multi-institutional Study Group of Pediatric Neurology. Seventy-six patients were collected from 10 institutions. Chromosome abnormalities included: Down syndrome (n = 19); Angelman syndrome (n = 8); Prader-Willi syndrome (n = 4); 4p- syndrome (n = 3); 1q- syndrome (n = 2); 5p- syndrome (n = 2); Miller-Dieker syndrome (n = 2); 18q- syndrome; (n = 2); Klinefelter syndrome; (n = 2); and 32 other individual chromosomal aberrations. Overall, the severity of mental retardation correlated with the severity of epilepsy. We could abstract characteristic features of epilepsy in some syndromes. In Angelman and Prader-Willi syndromes, febrile seizures occurred frequently, the onset of epilepsy was in early childhood and seizure phenotype was multiple. Paroxysmal discharge of the occipital region and diffuse high voltage slow wave on electroencephalography were characteristic in Angelman syndrome. In Down syndrome, West syndrome and focal epilepsy were common and the prognosis of epilepsy in West syndrome with Down syndrome was good. In 4p- syndrome, febrile seizures were often seen, and unilateral or generalized clonic or tonic-clonic status epilepticus were characteristic. For the other chromosomal aberrations investigated here, the patient numbers were too small to abstract common features of epilepsy.

Classical West “syndrome” phenotype with a subtelomeric 4p trisomy

We report a girl with mild mental retardation with onset of infantile spasms at age of 9 months. Treatment with a short course of adrenocorticotropic hormone (ACTH) was successful. Initially, a diagnosis of idiopathic West syndrome, with good neurological outcome and disappearance of epilepsy after treatment, was made. Conventional karyotype was normal. Reinvestigations were done at age 8 years, because of a new pregnancy. Karyotyping of both parents was done because of mild dysmorphic features in the proband, and to eliminate other causes than early age epilepsy as the etiology of her mental retardation. Parental karyotypes showed a balanced paternal translocation (4p;17q) resulting in partial 4p trisomy, without significant 17q monosomy in the proband. Chromosomal abnormalities usually lead to a severe West syndrome with poor prognosis of neurological outcome (persistent severe epilepsy, mental retardation, and behavioral disturbances). The presence of an undetected cytogenetic anomaly in our proband with transient hypsarythmia is unusual and led us to propose systematic telomeric screening in apparently "idiopathic" West syndrome patients with mild mental retardation and subtle dysmorphic features.

Infantile spasms in Down syndrome--effects of delayed anticonvulsive treatment

To investigate the impact of treatment lag in infantile spasms (IS) on treatment response, occurrence of later epilepsy, and long-term cognition and behavior in patients with one single etiological entity, we examined 18 patients with Down syndrome (DS) and earlier IS retrospectively (follow-up period of 32-180 months with a mean of 85.1 months), and determined their history and present condition, in terms of previously mentioned items. There was a statistically significant correlation between treatment lag and lag to cessation of spasms (R=0.55, P=0.02), developmental quotient (DQ) (R=-0.75, P=0.003), and score of autistic features (AF) (R=0.57, P=0.04). Moreover we found that the later the response to treatment of IS, the lower was the DQ (R=-0.86, P=0.001) and the higher was the score of autistic features (R=0.5, P=0.06). A long duration of spasms also determined a low DQ (R=-0.93, P<0.0001) and a high score of autistic features (R=0.66, P<0.01). All patients with persistent epilepsy (n=5) had had a treatment lag of over 2 months. Conversely, for all children treated within 2 months (n=8) spasms ceased within 3 months of treatment and none of them had later epilepsy. This group of patients with a treatment lag of less than 2 months had earlier treatment response (P=0.002), higher DQ (P=0.004) and lower score of autistic features (P=0.006). The data stress the importance of a short treatment lag in view of mental development and prevention of later epilepsy and autistic features, and raise the question of antiepileptogenic effect in this specific condition.

Down's syndrome

The sequencing of chromosome 21 and the use of models of Down's syndrome in mice have allowed us to relate genes and sets of genes to the neuropathogenesis of this syndrome, and to better understand its phenotype. Research in prenatal screening and diagnosis aims to find methods to identify fetuses with Down's syndrome, and reduce or eliminate the need for amniocentesis. Other areas of active research and clinical interest include the association of Down's syndrome with coeliac disease and Alzheimer's disease, and improved median age of death. Medical management of the syndrome requires an organised approach of assessment, monitoring, prevention, and vigilance. Improvements in quality of life of individuals with Down's syndrome have resulted from improvements in medical care, identification and treatment of psychiatric disorders (such as depression, disruptive behaviour disorders, and autism), and early educational interventions with support in typical educational settings. Approaches and outcomes differ throughout the world.

Infantile spasms: criteria for an animal model

Infantile spasms is an epilepsy syndrome with several distinctive features, including age specificity during infancy, characteristic semiology (epileptic spasms), specific electroencephalographic patterns (interictal hypsarrhythmia and ictal voltage suppression), and responsiveness to the adrenocorticotropic hormone (ACTH). There is no adequate animal model of infantile spasms, perhaps due to these clinically unique features, that is specific for the developing human brain. An informative animal model would provide insights into the pathophysiology of this syndrome and form the basis for the development of innovative therapies. This chapter considers criteria for an "ideal" animal model of infantile spasms, as well as "minimal" criteria that we consider essential to yield useful information. Two animal models of infantile spasms have been described in rodents: seizures induced by corticotropin-releasing factor and N-methyl-D-aspartic acid. Neither of these models conforms exactly to the human analog, but each possesses intriguing similarities that provide testable hypotheses for future investigations.

Infantile spasms in Down syndrome: good response to a short course of vigabatrin

PURPOSE

To evaluate the efficacy of vigabatrin (VGB) in the treatment of infantile spasms (ISs) associated with Down syndrome (DS) and to assess the feasibility of early discontinuation to reduce the possible retinal toxicity.

METHODS

Five children with ISs with DS were treated with vigabatrin as first-line monotherapy in an open prospective study. The short-term response was evaluated, and VGB was continued in responders. The treatment was stopped after 6 months in children who were still spasm free.

RESULTS

Four children of five became spasm free with VGB, three of them responding within 1 week. This response was maintained during the 6 months of VGB treatment. After VGB discontinuation, and with a follow-up ranging from 2 to 4 years, none of the responders experienced spasm recurrence or other types of seizures.

CONCLUSIONS

This study confirms the efficacy of VGB in ISs associated with DS. Moreover, it shows that the duration of VGB treatment can be reduced to 6 months without relapse of ISs. This short treatment might reduce the risk of developing visual field constriction.

West syndrome: long-term prognosis and social aspects

West syndrome (WS) is commonly associated with a poor long-term outcome including a small but significant mortality, infantile spasms that are resistant to treatment, the development of other seizure types and impaired cognitive and psychosocial functioning. It is important to understand that the families of these children also experience significant psychosocial morbidity, which is usually, but not invariably, correlated with persisting seizures beyond the first or second year of life. One of the fundamental points about the prognosis of this epilepsy syndrome is that the natural history (i.e. the outcome of spasms without any medical or surgical intervention) is not known. Numerous factors have been implicated as being important in influencing the long-term prognosis of children with WS. However, the majority of these factors have been identified from retrospective and markedly heterogeneous studies, including different populations and different treatment regimes. The most important prognostic factors are generally recognised to be the underlying aetiology of the syndrome and the presence or absence of pre-existing seizures and/or developmental abnormalities. The rapidity with which the diagnosis is made and treatment started from the onset of spasms (often termed the 'treatment lag') is a possible, though controversial and as yet unproven, factor in the prognosis of WS.