Basic science behind the catastrophic epilepsies

A long journey to treat epilepsy with the gut microbiota

Epilepsy is a common neurological disorder that affects approximately 10.5 million children worldwide. Approximately 33% of affected patients exhibit resistance to all available antiseizure medications, but the underlying mechanisms are unknown and there is no effective treatment. Increasing evidence has shown that an abnormal gut microbiota may be associated with epilepsy. The gut microbiota can influence the function of the brain through multiple pathways, including the neuroendocrine, neuroimmune, and autonomic nervous systems. This review discusses the interactions between the central nervous system and the gastrointestinal tract (the brain-gut axis) and the role of the gut microbiota in the pathogenesis of epilepsy. However, the exact gut microbiota involved in epileptogenesis is unknown, and no consistent results have been obtained based on current research. Moreover, the target that should be further explored to identify a novel antiseizure drug is unclear. The role of the gut microbiota in epilepsy will most likely be uncovered with the development of genomics technology.

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.

Integrated Macrogenomics and Metabolomics Explore Alterations and Correlation between Gut Microbiota and Serum Metabolites in Adult Epileptic Patients: A Pilot Study

Epilepsy (EP) is a complex brain disorder showing a lot of unknows reasons. Recent studies showed that gut microbiota can influence epilepsy via the brain-gut axis. Nevertheless, the mechanism by which gut microbiota affects adult epilepsy still remains unclear. In this study, fecal and serum samples were obtained from patients with epilepsy and normal controls. Using an integrated analysis, sequencing was performed by macrogenomics and high-throughput targeted metabolomics with various bioinformatics approaches. The macrogenomic sequencing revealed significant changes in microbial structure in patients suffering from epilepsy. For example, at the phylum level, the relative abundance of Actinobacteria, Bacteroidetes and Proteobacteria showed an increase in the patients with epilepsy, whereas that of Firmicutes decreased. In addition, the patients with epilepsy had significantly differential metabolite profiles compared to normal controls, and five clusters with 21 metabolites, mainly containing the upregulation of some fatty acids and downregulation of some amino acids. Tryptophan (AUC = 91.81, p < 0.0001), kynurenine (AUC = 79.09, p < 0.01) and 7Z,10Z,13Z,16Z-Docosatetraenoic acid (AUC = 80.95, p < 0.01) may be used as potential diagnostic markers for epilepsy. Differential serum metabolites have effects on tryptophan metabolism, iron death and other pathways. Furthermore, a multiomic joint analysis observed a statistically significant correlation between the differential flora and the differential serum metabolites. In our findings, a macrogenomic analysis revealed the presence of dysregulated intestinal flora species and function in adult epileptic patients. Deeper metabolomic analyses revealed differences in serum metabolites between patients with epilepsy and healthy populations. Meanwhile, the multiomic combination showed connection between the gut microbes and circulating metabolites in the EP patients, which may be potential therapeutic targets.

Seizure modulation by the gut microbiota and tryptophan-kynurenine metabolism in an animal model of infantile spasms

BACKGROUND

The infantile spasms syndrome is an early-onset epileptic encephalopathy presenting in the first 2 years of life, often with severe developmental consequences. The role of the gut microbiota and metabolism in infantile spasms remains unexplored.

METHODS

Employing a brain injury neonatal rat model of infantile spasms intractable to anticonvulsant medication treatments, we determined how the ketogenic diet and antibiotics affected specific microbial communities and the resultant circulating factors that confer spasms protection in the infantile spasms model. To confirm a role of kynurenine metabolism pathway in spasms protection, indoleamine 2,3-dioxygenase 1 was pharmacologically inhibited and comprehensive metabolomics was applied.

FINDINGS

We show that antibiotics reduced spasms and improved the effectiveness of the ketogenic diet when given in combination. Examination of the gut microbiota and metabolomics showed the downregulation of indoleamine 2,3-dioxygenase 1 and upregulation of hippocampal kynurenic acid, a metabolite with antiepileptic effects. To further test the involvement of indoleamine 2,3-dioxygenase 1, a specific antagonist 1-methyltryptophan and minocycline, an antibiotic and inhibitor of kynurenine formation from tryptophan, were administered, respectively. Both treatments were effective in reducing spasms and elevating hippocampal kynurenic acid. A fecal microbiota transplant experiment was then performed to examine the contribution of the gut microbiota on spasm mitigation. Transplant of feces of ketogenic diet animals into normal diet animals was effective in reducing spasms.

INTERPRETATION

These results highlight the importance of tryptophan-kynurenine metabolism in infantile spasms and provide evidence for new-targeted therapies such as indoleamine 2,3-dioxygenase 1 inhibition or microbiota manipulation to promote kynurenic acid production as a strategy to reduce spasms in infantile spasms.

FUNDING

This study was funded by the Alberta Children's Hospital Research Institute and the Owerko Centre.

Radiprodil, a NR2B negative allosteric modulator, from bench to bedside in infantile spasm syndrome

Objective

Infantile spasm syndrome (ISS) is an epileptic encephalopathy without established treatment after the failure to standard of care based on steroids and vigabatrin. Converging lines of evidence indicating a role of NR2B subunits of the N‐methyl‐D‐aspartate (NMDA) receptor on the onset of spams in ISS patients, prompted us to test radiprodil, a negative allosteric NR2B modulator in preclinical seizure models and in infants with ISS.

Methods

Radiprodil has been tested in three models, including pentylenetetrazole‐induced seizures in rats across different postnatal (PN) ages. Three infants with ISS have been included in a phase 1b escalating repeated dose study.

Results

Radiprodil showed the largest protective seizure effects in juvenile rats (maximum at PN12, corresponding to late infancy in humans). Three infants resistant to a combination of vigabatrin and prednisolone received individually titrated doses of radiprodil for up to 34 days. Radiprodil was safe and well tolerated in all three infants, and showed the expected pharmacokinetic profile. One infant became spasm‐free and two showed clinical improvement without reaching spasm‐freedom. After radiprodil withdrawal, the one infant continued to be spasm‐free, while the two others experienced seizure worsening requiring the use of the ketogenic diet and other antiepileptic drugs.

Interpretation

Radiprodil showed prominent anti‐seizure effect in juvenile animals, consistent with the prevalent expression of NR2B subunit of the NMDA receptor at this age in both rodents and humans. The clinical testing, although preliminary, showed that radiprodil is associated with a good safety and pharmacokinetic profile, and with the potential to control epileptic spasms.

Fenfluramine diminishes NMDA receptor-mediated seizures via its mixed activity at serotonin 5HT2A and type 1 sigma receptors

Fenfluramine exhibits antiepileptic properties and thus diminishes epileptiform discharges in experimental animal models of Dravet syndrome. Fenfluramine is metabolized into norfenfluramine in vivo, which shows greater affinity and agonist activity at serotonin 5HT2 receptors (5HT2R) than fenfluramine. In this study, we found that fenfluramine and norfenfluramine disrupted the regulatory association of the sigma 1 receptor (σ1R) with NR1 subunits of glutamate N-methyl-D-aspartate receptors (NMDAR), an effect that was also produced by σ1R antagonists such as S1RA and prevented by σ1R agonists such as PPCC. The antagonists removed σ1R bound to NMDAR NR1 subunits enabling calcium-regulated calmodulin (CaM) to bind to those subunits. As a result, CaM may inhibit calcium permeation through NMDARs. The serotoninergic activity of fenfluramine at 5HT2AR, and likely also at 5HT2CR, collaborated with its activity at σ1Rs to prevent the convulsive syndrome promoted by NMDAR overactivation. Notably, fenfluramine enhanced the inhibitory coupling of G protein-coupled receptors such as 5HT1AR and cannabinoid type 1 receptor with NMDARs, thus allowing the more effective restrain of NMDAR activity. Thus, fenfluramine circumvents the negative side effects of direct NMDAR antagonists and may improve the quality of life of subjects affected by such proconvulsant dysfunctions.

Increased precipitation of spasms in an animal model of infantile spasms by prenatal stress exposure

Infantile spasms (IS) represent a serious epileptic syndrome, called West syndrome (WS) that occurs in the early infantile age. Although several hypotheses and animal models have been proposed to explain the pathogenesis of IS, the pathophysiology of IS has not been elucidated. Recently, we proposed a hypothesis for IS under prenatal stress exposure (also called Zou's hypothesis) by correlating diverse etiologies and prenatal stresses with IS development. This research aims to determine the mechanism through which prenatal stress affects the offspring and establish the potential underlying mechanisms. Pregnant rats were subjected to forced swimming in cold water. Rat pups exposed to prenatal stress were administered with N-methyl-D-aspartate (NMDA). Exposure to prenatal stress sensitized the rats against development of NMDA-induced spasms. However, this phenomenon was altered by administering adrenocorticotropin. Prenatal stress exposure also altered the hormonal levels and neurotransmitter receptor expression of the developing rats as well as influenced the tissue structure of the brain. These findings suggest that maternal stress could alter the level of endogenous glucocorticoid, which is the basis of IS, and cerebral dysplasia, hypoxic-ischemic encephalopathy (HIE), inherited metabolic diseases, and other factors activated this disease in developmental brain.

Adrenocorticotropic hormone versus prednisolone in the treatment of infantile spasms post vigabatrin failure

The Child Neurology Society/American Academy of Neurology practice parameter has recommended adrenocorticotropic hormone or vigabatrin in the short-term treatment of infantile spasms. When vigabatrin is unavailable or ineffective and adrenocorticotropic hormone is not a treatment option because of the prohibitive cost, other forms of corticosteroids have been considered in the treatment of infantile spasms. This retrospective study reviewed the Hospital for Sick Children's experience with the short-term effectiveness of prednisolone versus adrenocorticotropic hormone in patients with infantile spasms who have failed vigabatrin. The results showed that while adrenocorticotropic hormone was more likely to lead to short-term spasm freedom, there was no difference in the likelihood of longer-term spasm resolution without relapse. These findings can guide clinicians in the treatment of infantile spasms post vigabatrin failure.

Outcomes of epilepsy surgery in childhood-onset epileptic encephalopathy

PURPOSE

to evaluate the outcomes and role of epilepsy surgery in children with intractable epileptic encephalopathy (EE).

METHODS

ninety-five children (64 boys, 31 girls) with intractable EE were treated by epilepsy surgery at Severance Children's Hospital from 2003 to 2008. Surgical treatments included lobar resection, hemispherotomy and corpus callosotomy (CC). Seventy-six children were Lennox-Gastaut syndrome (LGS), and 19 had West syndrome.

RESULTS

of the 76 patients with LGS, CC was performed in 37 patients (48.7%), lobar resection in 29 (38.2%) and hemispherotomy in 10 (13.2%). Of the 19 patients with West syndrome, respective surgery was performed in 15 patients (78.9%) and CC in 4 (21.1%). Of the patients receiving respective surgery, Engel's class I outcomes were achieved for 24 of 39 (61.5%) of LGS patients, and for 9 of 15 (60.0%) of West syndrome. Malformations of cortical development were commonly observed, appearing in 73.5% (36/49). In neuropsychiatric tests, 19 of 27 with LGS demonstrated improvement in postoperative cognitive function. More significant intellectual improvement correlated well with shorter epilepsy duration, good seizure outcomes, and decreased number of antiepileptic drugs.

CONCLUSIONS

epilepsy surgery should be considered in treating childhood intractable EE with expectation of improvement of both seizure and cognitive outcomes, even in cases of LGS.

Prenatal corticosteroids modify glutamatergic and GABAergic synapse genomic fabric: insights from a novel animal model of infantile spasms

Prenatal exposure to corticosteroids has long-term postnatal somatic and neurodevelopmental consequences. Animal studies indicate that corticosteroid exposure-associated alterations in the nervous system include hypothalamic function. Infants with infantile spasms, a devastating epileptic syndrome of infancy with characteristic spastic seizures, chaotic irregular waves on interictal electroencephalogram (hypsarhythmia) and mental deterioration, have decreased concentrations of adrenocorticotrophic hormone (ACTH) and cortisol in cerebrospinal fluid, strongly suggesting hypothalamic dysfunction. We have exploited this feature to develop a model of human infantile spasms by using repeated prenatal exposure to betamethasone and a postnatal trigger of developmentally relevant spasms with NMDA. The spasms triggered in prenatally primed rats are more severe compared to prenatally saline-injected ones and respond to ACTH, a treatment of choice for infantile spasms in humans. Using autoradiography and immunohistochemistry, we have identified a link between the spasms in our model and the hypothalamus, especially the arcuate nucleus. Transcriptomic analysis of the arcuate nucleus after prenatal priming with betamethasone but before trigger of spasms indicates that prenatal betamethasone exposure down-regulates genes encoding several important proteins participating in glutamatergic and GABAergic transmission. Interestingly, there were significant sex-specific alterations after prenatal betamethasone in synapse-related gene expression but no such sex differences were found in prenatally saline-injected controls. A pairwise relevance analysis revealed that, although the synapse gene expression in controls was independent of sex, these genes form topologically distinct gene fabrics in males and females and these fabrics are altered by betamethasone in a sex-specific manner. These findings may explain the sex differences with respect to both normal behaviour and the occurrence and severity of infantile spasms. Changes in transcript expression and their coordination may contribute to a molecular substrate of permanent neurodevelopmental changes (including infantile spasms) found after prenatal exposure to corticosteroids.

Biallelic SZT2 mutations cause infantile encephalopathy with epilepsy and dysmorphic corpus callosum

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies.

An effective initial polytherapy for children with West syndrome

Adrenocorticotropic hormone is recommended worldwide as an initial therapy for infantile spasms. However, infantile spasms in about 50% of children cannot be fully controlled by adrenocorticotropic hormone monotherapy, seizures recur in 33% of patients who initially respond to adrenocorticotropic hormone monotherapy, and side effects are relatively common during adrenocorticotropic hormone treatment. Topiramate, vitamin B₆, and immunoglobulin are effective in some children with infantile spasms. In the present study, we hypothesized that combined therapy with adrenocorticotropic hormone, topiramate, vitamin B₆, and immunoglobulin would effectively treat infantile spasms and have mild adverse effects. Thus, 51 children newly diagnosed with West syndrome including infantile spasms were enrolled and underwent polytherapy with the four drugs. Electroencephalographic hypsarrhythmia was significantly improved in a majority of patients, and these patients were seizure-free, had mild side effects, and low recurrence rates. The overall rates of effective treatment and loss of seizures were significantly higher in cryptogenic children compared with symptomatic children. The mean time to loss of seizures in cryptogenic children was significantly shorter than in symptomatic patients. These findings indicate that initial polytherapy with adrenocorticotropic hormone, topiramate, vitamin B₆, and immunoglobulin effectively improves the prognosis of infantile spasms, and its effects were superior in cryptogenic children to symptomatic children.

Prenatal stress exposure hypothesis for infantile spasms

Infantile spasms (IS) are an age-specific epileptic syndrome associated with diverse etiological factors. In recent years, several hypotheses and animal models have been proposed to explain the pathogenesis of IS, but none has elucidated the pathophysiology of IS. In the current case-control study, prenatal stress degree was identified to be higher among the mothers of IS patients than those among the control group. The onset risk of IS increased with the degree of prenatal stress within a certain range. We have recently exposed pregnant rats to forced cold swimming and have given intraperitoneal injection of N-methyl-d-aspartate (NMDA) to rat pups with prenatal stress exposure. Prenatal stress exposure was found to alter the hormonal levels and neurotransmitter receptor expression of developing rats, sensitizing rat pups to develop NMDA-induced spasms and rendering the spasms to be sensitive to adrenocorticotropic hormone therapy. The studies above indicate that prenatal stress plays an important role in the onset of IS. Based on previous hypotheses and the current findings, we propose a prenatal stress exposure hypothesis for IS (also called Zou's hypothesis).

A diagnostic algorithm for the evaluation of early onset genetic-metabolic epileptic encephalopathies

Early onset epileptic encephalopathies represent a struggling challenge in neurological clinical practice, mostly in infants and very young children, partly due to an unclear and still debated cathegorization. In this scenario genetic and metabolic epileptic encephalopathies play a central role, with new entries still needing an arrangement. In this Paper we present a brief overview on genes, metabolic disorders and syndromes picturing the pathogenesis of genetic and metabolic epileptic encephalopathies with onset under one year of age. These forms will be classified, according to a combined clinical and genetic-metabolic criterion, into two main groups including seizures as prominent/unique symptom and seizures associated with a syndromic phenotype. Starting from this classification we suggest a possible simplified diagnostic algorithm, discussing main decision making nodes in practical patients management. The aim of the proposed algorithm is to guide through metabolic and molecular-genetic work up and to clarify "where" and "what" to search in biochemical, electroencephalographic and neuroimaging investigations.

Treatment of infantile spasms: emerging insights from clinical and basic science perspectives

Infantile spasms is an epileptic encephalopathy of early infancy with specific clinical and electroencephalographic (EEG) features, limited treatment options, and a poor prognosis. Efforts to develop improved treatment options have been hindered by the lack of experimental models in which to test prospective therapies. The neuropeptide adrenocorticotropic hormone (ACTH) is effective in many cases of infantile spasms, although its mechanism(s) of action is unknown. This review describes the emerging candidate mechanisms that can underlie the therapeutic effects of ACTH in infantile spasms. These mechanisms can ultimately help to improve understanding and treatment of the disease. An overview of current treatments of infantile spasms, novel conceptual and experimental approaches to infantile spasms treatment, and a perspective on remaining clinical challenges and current research questions are presented here. This summary derives from a meeting of specialists in infantile spasms clinical care and research held in New York City on June 14, 2010.

1H MRSI and social communication deficits in pediatric complex partial seizures

PURPOSE

To investigate relationships between regional brain metabolites, social communication deficits, and seizure frequency in children and adolescents with cryptogenic epilepsy with complex partial seizures (CPS).

METHODS

In 12 children and adolescents with CPS and 23 age- and gender-matched healthy controls, we acquired proton magnetic resonance spectroscopic imaging (MRSI) at 1.5 T and 30 ms echo-time from bilateral inferior frontal and superior temporal gyri, regions associated with social communication deficits. Videotaped speech samples of all the subjects were coded for social communication deficits and parents provided information on seizure frequency.

KEY FINDINGS

Four MRSI findings emerged in right inferior frontal gyrus. N-acetyl-aspartate (NAA) plus N-acetyl-aspartyl-glutamate (NAAG)--together called "tNAA"--was 11.4% lower in patients with CPS than in controls. Choline-compounds (Cho) were 15.4% lower in CPS than in controls. Within CPS, higher tNAA was associated with more frequent seizures and abnormal social communication.

SIGNIFICANCE

Localization of findings to right inferior frontal cortex supports the involvement of this area in social communication deficits and may be related to atypical lateralization of expressive language in pediatric epilepsy. Lower levels of tNAA and Cho may indicate local neuronal or glial damage or underpopulation due to excitotoxicity or other causes. The sensitivity of tNAA to seizure frequency suggests effects of ongoing CPS on neuronal and glial function in this brain region.

A possible association of responsiveness to adrenocorticotropic hormone with specific GRIN1 haplotypes in infantile spasms

AIM

Adrenocorticotropic hormone (ACTH) has been used as the major therapy for infantile spasms since 1958 because it effectively suppresses seizures; it also normalizes the electroencephalogram in the short-term treatment of infantile spasms. G protein-regulated inducer of neurite outgrowth 1 (GRIN1, also known as N-methyl-D-aspartate receptor 1, NMDAR1), a glutamate receptor, is the main component of functional N-methyl-D-aspartic acid receptors that are involved in the glucocorticoid-induced neuronal damage. Thus, it may be a candidate gene to be tested for responsiveness to ACTH in infantile spasms. In the present study, polymorphisms in the GRIN1 gene in infantile spasms were investigated using a case-control design.

METHOD

Twelve single nucleotide polymorphisms in the GRIN1 gene were genotyped in a Chinese case-control set consisting of 97 unrelated patients with infantile spasms (60 males, 37 females; mean age 6.4 mo, SD 2.7) and 96 healthy individuals (63 males, 33 females; mean age 7.3 mo, SD 3.8). Association analysis was performed on the genotyped data.

RESULTS

Five estimated haplotypes with a frequency of more than 3% were detected. Results of the study showed that responsiveness to treatment with ACTH in homozygous carriers of the CTA haplotype was higher than that in heterozygous carriers and non-carriers (p=0.022). Furthermore, CTG, a rare haplotype, was strongly associated with infantile spasms (p=0.013).

INTERPRETATION

The results suggest that haplotypes of GRIN1 may influence responsiveness to ACTH. The findings necessitate further study for confirmation.

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.

Cerebrospinal fluid pterins and neurotransmitters in early severe epileptic encephalopathies

Early-onset epileptic encephalopathies are devastating conditions. Little is known about pathophysiology and biological markers. We aimed to identify a relationship between the type and prognosis of epileptic encephalopathies starting in infancy and the cerebrospinal fluid profile of pterins and neurotransmitters. Cerebrospinal fluid samples of 23 infants with epileptic encephalopathies were analysed for biogenic amine metabolites (homovanillic and 5-hydroxyindoleacetic acids), and pterins (neopterin and biopterin). West syndrome, early-infantile epileptic encephalopathy with suppression-bursts or Ohtahara syndrome, severe epilepsy with multiple independent spike foci and partial epilepsy with multiple independent spike foci were the four types of epileptic encephalopathy studied. We report clinical, electroencephalographic, neuroimaging and follow-up data. Among the 23 patients studied, 7 had high neopterin levels. Four of them had partial epilepsy with multiple independent spike foci. High neopterin values were associated with mortality (chi square = 7.304, p = 0.007). 5-Hydroxyindoleacetic acid levels were above reference values in three patients, two with partial epilepsy with multiple independent spike foci and one with West syndrome. Homovanillic acid was normal in almost all infants studied. In conclusion, high neopterin levels suggest a cellular immune activation in the central nervous system of these infants, with apparent prognosis implications.

Can fever treat epileptic encephalopathies?

PURPOSE

To describe resistant epileptic encephalopathies that significantly improved after an acute febrile episode (FE).

METHODS

We reviewed the clinical history of patients with daily pharmacoresistant seizures referred to the Saint-Vincent de Paul Hospital in the last 5 years. Four patients experienced seizure arrest in relation with a febrile episode.

RESULTS

The four patients suffered from epileptic encephalopathy. Three were symptomatic, one cryptogenic. They presented spasms and atypical absences, beginning after the age of 1 year. All seizures stopped at the onset of fever, and significant EEG improvement was observed. The seizure-free period ranged from 2 to 24 months.

DISCUSSION AND CONCLUSION

The close link between the occurrence of FE and the disappearance of seizures and EEG improvement, contrasting with the previous pharmacoresistance of this epileptic encephalopathy, supports a non fortuitous association. Several mechanisms could explain this phenomenon, including viral etiology, hyperthermia, inflammatory-immune reaction and ACTH release. Better understanding this phenomenon could open new therapeutic perspectives.

Model of infantile spasms induced by N-methyl-D-aspartic acid in prenatally impaired brain

OBJECTIVE

Infantile spasms (a catastrophic epileptic syndrome of childhood) are insensitive to classic antiepileptic drugs. New therapies are limited by lack of animal models. Here we develop a new model of flexion spasms based on prenatal exposure to betamethasone combined with postnatal administration of N-methyl-D-aspartic acid (NMDA) and determine brain structures involved in the induction of flexion spasms.

METHODS

Pregnant rats received two doses of betamethasone on day 15 of gestation. Offspring was injected with NMDA on postnatal day 15. Effects of adrenocorticotropin therapy on the development of age-specific flexion spasms were determined and electroencephalographic correlates recorded. C-fos immunohistochemistry and [14C]2-deoxyglucose imaging identified brain structures involved in the development of flexion spasms.

RESULTS

Prenatal betamethasone exposure sensitizes rats to development of NMDA-induced spasms and, most importantly, renders the spasms sensitive to adrenocorticotropin therapy. Ictal electroencephalogram results correspond to human infantile spasms: electrodecrement or afterdischarges were observed. Imaging studies defined three principal regions involved in NMDA spasms: limbic areas (except the dorsal hippocampus), hypothalamus, and the brainstem.

INTERPRETATION

Despite certain limitations, our new model correlates well with current infantile spasm hypotheses and opens an opportunity for development and testing of new effective drugs.

Pediatric intractable epilepsy syndromes: reason for early surgical intervention

Drug-resistance in several childhood epilepsy syndromes is common, and these patients may tolerate epilepsy surgery. In this study, the surgical outcomes of 24 pediatric patients with various intractable epilepsy syndromes and three patients with tuberous sclerosis were examined at Xinqiao hospital between 1997 and 2004. The study included nine cases of Lennox-Gastaut syndrome, two cases of Rasmussen's syndrome, one case of Sturge-Weber syndrome, three cases of West syndrome, three cases of tuberous sclerosis and nine cases of mesial temporal lobe epilepsy syndrome. In each case, different surgical procedures were performed according to preoperative evaluation and ECoG. At an average of 4.5 years after surgery, 14 out of 27 patients (51.9%) had an Engel Class I outcome after surgery, and an additional eight patients (29.6%) had rare seizure (Engel ClassII). Three patients showed a significant decrease in seizure frequency (Engel Class III). The mean IQ increased from 61.4+/-12.2 to 75.0+/-11.0, and greater IQ increase was seen in patients with shorter seizure history and drug-resistance. Temporary complications were observed in four patients and there were no deaths. In conclusion, early surgical intervention in pediatric intractable epilepsy syndromes may results in a favorable outcome in a high percentage of cases and may provides an important opportunity to prevent irreversible decline in intelligence and disability.

The Risk of Lower Mental Outcome in Infantile Spasms Increases after Three Weeks of Hypsarrhythmia Duration

To assess the correlation between hypsarrhythmia duration and mental outcome in infantile spasms (IS) the medical records of 48 infants with IS were reviewed retrospectively and psychological assessments undertaken at follow-up at the age of 3 to 13 years. We found 18 (38%) cryptogenic IS cases with typical hypsarrhythmia and 30 symptomatic with modified hypsarrhythmia-further classified into 15 cases as multifocal, 10 as pseudoperiodic and 5 as unilateral hypsarrhythmia. A short treatment lag (one to two weeks) occurred in 25, three to four weeks in 10 cases. Spasms ceased within one month after treatment in 23 infants. At follow-up 15 children had normal mental outcome (borderline included). A correlation between hypsarrhythmia duration longer than three weeks and lower mental outcome was found using the logistic regression model. The duration of hypsarrhythmia represents a sensitive prognostic parameter in IS; the risk of mental retardation increases after three weeks of hypsarrhythmia.

Daily rhythms of seizure activity and behavior in a model of atypical absence epilepsy

We studied daily rhythms of chronic seizure activity and behavior in adult rats and mice treated with the cholesterol biosynthesis inhibitor AY-9944 (AY) during early postnatal development. Chronic atypical absence seizures were verified in the AY-treated animals by the presence of spontaneous 5- to 6-Hz slow spike-wave discharges (SSWDs) in the neocortex. General behavioral activity, as measured by total movements (TM), movement time (MT), ambulatory movement time (AMT), time spent in center of arena (CT), jumps (JFP), and rotational behavior (TURNS), were continuously recorded under a 12-hour light:12-hour dark photocycle. The average SSWD duration in AY-treated rats varied daily, with two peaks occurring at approximately dark phase and light phase onset. Mice treated with AY exhibited significant increases in all behavioral measures during the light and dark phases, with the exception of light-phase CT, which did not differ from that of controls. Consequently, the daily rhythm of total behavioral activity (TM) exhibited a significantly higher mean oscillation (mesor) and amplitude without evidence of phase shift compared with the TM rhythm of controls. The occurrence of SSWD activity in the AY model appears to be subject to regulation by biological timing mechanisms and, furthermore, associated with motor hyperactivity that does not alter the timing of behavioral rhythmicity.

Treatment of infantile spasms

Infantile spasms are associated with a diverse range of conditions, and treatment options are available. However, outcomes remain generally poor, particularly for those with symptomatic etiologies. First-line therapy is considered to be hormonal (adrenocorticotropic hormone; ACTH), which some evidence suggests is more effective when started early. However, side effects may place limits on its use acutely and long-term. There is additional evidence for vigabatrin, specifically for infantile spasms secondary to tuberous sclerosis complex. In refractory cases, candidacy for surgical management should be explored, along with new-generation anticonvulsants (eg, topiramate, zonisamide) and the ketogenic diet. There is urgent need for further treatment trials comparing anticonvulsants with ACTH and a satisfactory animal model for the study of spasms.

Head growth in infants with infantile spasms may be temporarily reduced

Epileptic activity, as a component of epileptic encephalopathies, can interfere with brain growth and development. Infantile spasms as a syndrome represent such epileptic activity during the period of spasms and hypsarrhythmia. The rate of head growth in infants with infantile spasms during the period of spasms has not been studied previously. A retrospective study of head growth in 38 infants with infantile spasms and no other cause of abnormal head growth is presented. Mental outcome was assessed at follow-up. The mean head circumference of infants with infantile spasms was not significantly smaller than in the normal population, but the proportion of head circumference below the tenth percentile in the infantile spasms group was higher (27%). Head circumference below the tenth percentile in the fourth and fifth month after the onset of infantile spasms was significantly associated with later mental retardation (P = 0.004). There was no correlation with specific treatment of infantile spasms. Transiently diminished head growth in infants with infantile spasms coincides temporally with the onset of infantile spasms and "catches up" during remission of infantile spasms in favorable cases. This pattern can reflect the negative influence of epileptic activity on brain growth during the sensitive period. Head circumference can provide a reliable predictive value of mental outcome in children with infantile spasms.

Recognition and management of pediatric seizures

It is not unusual for the primary care provider to have a child present with unusual paroxysmal events or dermatological lesions that bear further investigation. Although most children with epilepsy are treated and managed by pediatric neurologists, it is imperative that the primary care provider have a clear understanding of associated comorbidities, as well as information on the available anti-epileptic drugs, their side effects, and the need for further monitoring. Those children with epilepsy whose seizures become intractable, failing to be controlled with three or more medications used appropriately at adequate doses, should be referred to a comprehensive epilepsy center for consideration for other treatments. These may include the ketogenic diet, vagal nerve stimulation, or epilepsy surgery.

The latest on infantile spasms

PURPOSE OF REVIEW

This article reviews the most significant advances in the field of infantile spasm during the past year, with emphasis on best practise for treatment, and on some new etiological genetic and metabolic causes for the spasms, and new advances in the knowledge of tuberous sclerosis.

RECENT FINDINGS

Up-to-date information comparing corticotrophin, oral steroids and vigabatrin shows that hormonal treatment is the most effective therapy in the short term. In a recent randomized trial, large doses of prednisolone were as effective as corticotrophin. There are insufficient data to recommend any treatment schedule for infantile spasms. Vigabatrin is the choice for infants with tuberous sclerosis. Visual field defects in (older) children seem to be as common as in adults. In animals, vigabatrin can induce apoptosis of the neurons in the developing brain. New rare factors associated with infantile spasms are mitochondrial diseases, mutations of the Aristales-related homeobax gene and posterior quadrantic dysplasia syndrome. The outcome in children with tuberous sclerosis and infantile spasms is better understood.

SUMMARY

The accurate determination of etiology is now becoming increasingly possible. There is still a lack of consensus about the treatment of first choice for infantile spasms. However, recent data show that hormonal treatment is the most effective therapy in the short term. Frequency of visual field defects in children treated with vigabatrin should be studied in addition to the long-term outcome in general. Advances in our understanding of brain maturation, etiologies, mechanisms and genetics underlying catastrophic epilepsy may facilitate more effective pharmacologic interventions.