A retrospective analysis of patients with febrile seizures followed by epilepsy

Immune Challenges and Seizures: How Do Early Life Insults Influence Epileptogenesis?

The development of epilepsy, a process known as epileptogenesis, often occurs later in life following a prenatal or early postnatal insult such as cerebral ischemia, stroke, brain trauma, or infection. These insults share common pathophysiological pathways involving innate immune activation including neuroinflammation, which is proposed to play a critical role in epileptogenesis. This review provides a comprehensive overview of the latest preclinical evidence demonstrating that early life immune challenges influence neuronal hyperexcitability and predispose an individual to later life epilepsy. Here, we consider the range of brain insults that may promote the onset of chronic recurrent spontaneous seizures at adulthood, spanning intrauterine insults (e.g. maternal immune activation), perinatal injuries (e.g. hypoxic–ischemic injury, perinatal stroke), and insults sustained during early postnatal life—such as fever-induced febrile seizures, traumatic brain injuries, infections, and environmental stressors. Importantly, all of these insults represent, to some extent, an immune challenge, triggering innate immune activation and implicating both central and systemic inflammation as drivers of epileptogenesis. Increasing evidence suggests that pro-inflammatory cytokines such as interleukin-1 and subsequent signaling pathways are important mediators of seizure onset and recurrence, as well as neuronal network plasticity changes in this context. Our current understanding of how early life immune challenges prime microglia and astrocytes will be explored, as well as how developmental age is a critical determinant of seizure susceptibility. Finally, we will consider the paradoxical phenomenon of preconditioning, whereby these same insults may conversely provide neuroprotection. Together, an improved appreciation of the neuroinflammatory mechanisms underlying the long-term epilepsy risk following early life insults may provide insight into opportunities to develop novel immunological anti-epileptogenic therapeutic strategies.

Reduced cerebrospinal fluid levels of interleukin-10 in children with febrile seizures

PURPOSE

The exact etiology of febrile seizures (FS) is still unclear. However, it is thought that cytokine network activation may have a causative role. Therefore, this study aimed to evaluate the levels of interleukin-12 (IL-12) as a proinflammatory cytokine, interleukin-10 (IL-10) as an anti-inflammatory cytokine, and interferon-β (IFN-β), a marker of toll-like receptor-3 activation as a host response to viruses. These cytokine levels were analyzed in the cerebrospinal fluid (CSF) of children after a FS.

METHODS

With the approval of the Human Research Ethics Committee, 76 patients with FS, who underwent lumbar puncture (LP) for the exclusion of central nervous system (CNS) infection, and who didn't have CSF pleocytosis, were included in the study. The control group consisted of 10 patients with similar ages, with an acute febrile illness and who required LP to exclude CNS infection. The analyses were made by the enzyme-linked immunoassay method.

RESULTS

Age, gender distribution and CSF IL-12 and IFN- β levels did not differ, but CSF IL-10 levels were significantly lower in the FS group as compared to the control group (0.78 ± 4.5 pg/ml, versus 27 ± 29 pg/ml, p < 0.0001).

CONCLUSION

The low-level of CSF IL-10, considering its anti-inflammatory properties, may play a role in the etiopathogenesis of FS.

Association of developing childhood epilepsy subsequent to febrile seizure: A population-based cohort study

PURPOSE

Epilepsy is an important neurological condition that frequently associated with neurobehavioral disorders in childhood. Our aim was to identify the risk of developing epilepsy subsequent to febrile seizure and the association between epilepsy risk factors and neurobehavioral disorders.

SUBJECTS AND METHODS

This longitudinal population-based cohort data included 952 patients with a febrile seizure diagnosis and 3808 age- and sex-matched controls. Participants were recruited for the study from 1996 to 2011, and all patients were followed up for maximum 12.34 years.

RESULTS

The association of epilepsy was significantly higher (18.76-fold) in individuals that experienced febrile seizure compared to controls. Further, of those individuals who experienced febrile seizure, the frequency of subsequent development of epilepsy was 2.15-fold greater in females, 4.846-fold greater in patients with recurrent febrile seizure, and 11.26-fold greater patients with comorbid autism.

CONCLUSIONS

Our study showed that being female, comorbid autism with febrile seizure and recurrent febrile seizure had an increased association with development of epilepsy. Increased recognition the association for epilepsy might be warranted in those febrile seizure children with certain characteristics.

Predictors of unprovoked seizure after febrile seizure: short-term outcomes

INTRODUCTION

We performed this study to confirm the known risk factors and to identify possible new risk factors for subsequent unprovoked seizure after febrile seizure (FS) on Jeju Island, South Korea.

METHODS

A population-based retrospective study of 204 children with FS, whose first FS developed between March 2003 and August 2011, and who were seen in the Pediatric Department at the Jeju National University Hospital.

RESULTS

Two hundred four children (136 boys and 68 girls) were enrolled in this study. Simple FS was found in 107 children, and complex FS was found in 97 children. The average age at the first FS was 18.9 months. The average total number of FSs was 4.3. A family history of FS or epilepsy was found in 29.4% and 7.8% of patients, respectively. Abnormal findings of EEG were observed in 35.8%. Complex features in the first FS were noted in 28.9%. Subsequent unprovoked seizures occurred in 23.0%. Univariate analysis showed that low parental educational level was one of several variables that were significantly related to unprovoked seizure. Parental educational level was not included in the multivariate model because of an insufficient sample size. Multivariate analysis identified the following factors as significant predictors of unprovoked seizure: late onset of FS at age>3 years, complex features in the first FS, family history of epilepsy, and abnormal findings on EEG, and FS developed at a body temperature of <39°C.

CONCLUSIONS

We confirmed the known risk factors for subsequent unprovoked seizure and found that low parental educational status may be a new prognostic indicator. However, further investigation using larger populations and a prospective design is needed to confirm that this is a valid prognostic factor for FS.

Prognostic factors for subsequent epilepsy in children with febrile seizures

OBJECTIVE

Epilepsy following febrile seizures (FS) has been estimated between 2% and 7%. It concerns a prospective study in a large sample of children with a long-term follow-up. The aim of this study is to identify the prognostic factors that can lead children with FS to epilepsy.

METHODS

Children with a first episode of FS were included. We gathered information about prenatal and perinatal history, family history of FS and epilepsy in first- and second degree relatives, age at the time of the initial FS, dates of FS recurrences, focality, duration of the FS and recurrent episodes within the same febrile illness, height and duration of fever prior to the seizure, cause of the fever, and frequency of febrile illnesses. Patients were seen every 4-6 months and also at each recurrence.

KEY FINDINGS

A group of 560 children with a first FS met all entry criteria. Epilepsy was recorded at 5.4%. Statistical analysis was performed between children with epilepsy and those with no afebrile seizure. We analyzed FS recurrences in accordance with the occurrence of epilepsy. From the third FS recurrence and beyond, only focality continued to have prognostic value.

SIGNIFICANCE

Main prognostic factors for the development of epilepsy after FS are: (1) complex FS that increased the risk for epilepsy 3.6 times, (2) age at onset of FS beyond the third year of life that raised the risk 3.8 times, (3) positive family history of epilepsy 7.3 times, and (4) multiple episodes of FS about 10 times. Focality at the first and the second FS recurrence increased the risk of epilepsy about 9.7 and 11.7 times, respectively. Focality was the only factor that continued to be significant in further FS recurrences. A prognostic profile of each child with FS would be very useful for the follow-up of these children.

Expression analysis and clinical correlation of aquaporin 1 and 4 genes in human hippocampal sclerosis

Mesial temporal sclerosis (MTS) is the most frequent cause of drug resistant symptomatic partial epilepsy. The mechanism and genetic background of this unique pathology are not well understood. Aquaporins (AQP) are regulators of water homeostasis in the brain and are expressed in the human hippocampus. We explored the role of AQP genes in the pathogenetic mechanisms of MTS through an evaluation of gene expression in surgically removed human brain tissue. We analyzed AQP1 and 4 mRNA levels by quantitative real-time polymerase chain reaction and normalized to ABL and cyclophilin genes, followed by immunohistochemistry for AQP4. Relative expressions were calculated according to the delta Ct method and the results were compared using the Mann-Whitney U test. Brain specimens of 23 patients with epilepsy who had undergone surgery for MTS and seven control autopsy specimens were investigated. Clinical findings were concordant with previous studies and 61% of the patients were seizure-free in the postoperative period. AQP1 and 4 gene expression levels did not differ between MTS patients and control groups. Immunofluorescence analysis of AQP4 supported the expression results, showing no difference. Previous studies have reported contradictory results about the expression levels of AQP in MTS. To our knowledge, only one study has suggested upregulation whereas the other indicated downregulation of perivascular AQP4. Our study did not support these findings and may rule out the involvement of AQP in human MTS.

Mesial temporal sclerosis in children

Mesial temporal sclerosis is the most frequent cause of drug-resistant temporal lobe epilepsy but has a satisfactory response to surgery, and is considered infrequent in children. OBJECTIVE: To evaluate the clinical, electrographic and radiological spectrum of the disease in children. METHOD: Retrospective study by review of charts of 44 children with a diagnosis of mesial temporal sclerosis on magnetic resonance imaging, attended at the "Hospital das Clínicas" of the University of São Paulo Faculty of Medicine. RESULTS: Febrile seizure was identified in the history of 54% of the patients. Injuries at the left side predominated in patients with schooling difficulties (p=0.049), in those with the first seizures between six months and five years (p=0.021) and in those with complex febrile seizure (p=0.032). Thirteen patients were submitted to surgery and of these, eight remained without seizures. CONCLUSION: Febrile seizure may be related in a more direct way to the presence of left-side mesial temporal sclerosis.

Familial genetic predisposition, epilepsy localization and antecedent febrile seizures

PURPOSE

The magnitude of genetic influence in epilepsy may vary in relation to epilepsy classification and localization and factors such as antecedent febrile seizures. We assessed this genetic influence in a large epilepsy population.

METHODS

Patients with established epilepsy diagnosis evaluated in the Vanderbilt Epilepsy Program were systematically questioned about family history of epilepsy and febrile seizures, prior febrile seizures and other risk factors for epilepsy.

RESULTS

A total of 1994 patients with epilepsy and reliable family history were identified. Patients with prior febrile seizures (FS) were more likely to have a family history of febrile seizures than those without prior FS (p<0.000001) and also had a greater proportion of relatives with febrile seizures. The groups did not differ with respect to family history of epilepsy. Patients with generalized epilepsy were more likely to have first and second degree relatives with epilepsy than those with partial epilepsy (40.2% versus 31.2%, p=0.001), and also had a greater proportion of affected first degree relatives (p<0.000001). The proportion of first degree relatives affected with epilepsy was higher than local published prevalence, for both groups.

CONCLUSION

Susceptibility for febrile seizures with subsequent epilepsy may be genetically distinct from susceptibility for afebrile seizures alone. Although family history of epilepsy was more likely with generalized epilepsy, a familial tendency was considerable in partial epilepsy.

Childhood mesial temporal sclerosis

The prevalence and clinical characteristics of mesial temporal sclerosis have not been well studied in children. All brain magnetic resonance imaging (MRI) reports of children less than 14 years of age were reviewed from two tertiary institutions. A 52-month period from one institution and a 37-month period from the other were reviewed. All reports of definite or possible mesial temporal sclerosis were noted. These patients' MRIs were then reviewed to confirm the MRI diagnostic criteria of mesial temporal sclerosis. The charts of the patients who satisfied these criteria were reviewed in detail. Three thousand one hundred brain MRI reports were reviewed. Twenty-six reports of mesial temporal sclerosis were found. Twenty-four of the 26 films satisfied the criteria of mesial temporal sclerosis by MRI after the films were reviewed. The prevalence among all pediatric brain MRI studies was 0.77%. All patients had presented with seizures, that is, there were no "incidental" findings of mesial temporal sclerosis. Four patients had a history of febrile seizures. Mesial temporal sclerosis is an uncommon finding in children, but when it occurs, it is always associated with epilepsy. Asymptomatic mesial temporal sclerosis or mesial temporal sclerosis not associated with a seizure disorder did not occur in our series. Febrile seizures can occur in association with mesial temporal sclerosis presenting in childhood.

Febrile convulsions induced by the combination of lipopolysaccharide and low-dose kainic acid enhance seizure susceptibility, not epileptogenesis, in rats

PURPOSE

Febrile convulsions (FCs) are seizures that occur as a result of fever. Retrospective clinical studies show a large percentage of adults with temporal lobe epilepsy have a positive history of FCs, but it is unknown whether FCs during infancy alter susceptibility to developing late epilepsy. We have tested the hypothesis that FCs affect seizure susceptibility and epileptogenesis in adults.

METHODS

A novel model of FCs was used, in which lipopolysaccharide (LPS, Escherichia coli), in combination with a subconvulsant dose of kainic acid, caused FCs in 50% of 14-day-old male rats. Eight to 10 weeks later, electrodes were implanted into the basolateral amygdalae of all rats. After completion of the kindling procedure, animals were killed and brains examined for neurodegeneration by using Fluoro-Jade histochemistry.

RESULTS

Amygdala stimulation revealed that rats that had a FC as pups had lower afterdischarge thresholds and longer afterdischarge durations when compared with rats that received the same treatment but did not convulse. Despite this, when kindled daily, rats that had FCs as pups kindled at the same rate as did controls. However, an increase in the number of degenerating neurons was noted within the hippocampus of rats with a previous FC.

CONCLUSIONS

These results suggest that, although FCs during infancy can reduce seizure thresholds, it does not facilitate epileptogenesis in adulthood. Our results indicate that FCs affected local circuits in the amygdala and possibly in the hippocampus but not circuits responsible for seizure generalization.

Causal links between brain cytokines and experimental febrile convulsions in the rat

PURPOSE

Despite the prevalence of febrile convulsions (FCs), their pathophysiology has remained elusive. We tested the hypothesis that components of the immune response, particularly the proinflammatory cytokine interleukin-1beta (IL-1beta) and its naturally occurring antagonist interleukin-1 receptor antagonist (IL-1ra) may play a role in the genesis of FC.

METHODS

Postnatal day 14 rats were treated with lipopolysaccharide (LPS; 200 microg/kg, i.p.) followed by a subconvulsant dose of kainic acid (1.75 mg/kg, i.p.). Brains were harvested at and 2 h after onset of FCs to measure brain levels of IL-1beta and IL-1ra. Separate groups of animals were given intracerebroventricular (ICV) injections of IL-1beta, or IL-1ra in an attempt to establish a causal relation between the IL-1beta/IL-1ra system and FCs.

RESULTS

Animals with FCs showed increased IL-1beta in the hypothalamus and hippocampus but not in the cortex compared with noFC animals that also received LPS and kainic acid. This increase was first detected in the hippocampus at onset of FCs. No detectable difference in IL-1ra was found in brain regions examined in either group. When animals were treated with IL-1beta ICV, a dose-dependant increase was noted in the proportion of animals that experienced FCs, whereas increasing doses of IL-1ra, given to separate groups of animals, were anticonvulsant.

CONCLUSIONS

Our results suggest that excessive amounts of IL-1beta may influence the genesis of FCs. This may occur by overproduction of IL-1beta, or by alteration in the IL-1beta/IL-1ra ratio in the brain after an immune challenge.

Quantitative HMRS and MRI volumetry indicate neuronal damage in the hippocampus of children with focal epilepsy and infrequent seizures

PURPOSE

Seizures induce progressive morphologic and functional changes in particular in the hippocampus, but whether and at what stage the hippocampus is affected in children with focal, temporal, nonintractable epilepsy is poorly known. We have now studied eventual metabolic and volume changes in the hippocampus of children with nonsymptomatic focal epilepsy taking antiepileptic medication (AEDs) but still having infrequent seizures.

METHODS

Quantitative proton magnetic resonance spectroscopy ((1)HMRS) and volumetric MRI were used to study the hippocampal region of 11 pediatric outpatients (age 10 to 17 years) with cryptogenic localization-related epilepsy, and eight healthy volunteers (age 9 to 16 years) served as controls. The spectra were obtained bilaterally from the hippocampi by using the 1.5-T MR imager. The spectral resonance lines of N-acetyl group (NA), creatine and phosphocreatine group (Cr), choline-containing compounds (Cho), and myoinositol (mI) were analyzed quantitatively. The volume of the hippocampus was semiautomatically calculated.

RESULTS

The mean concentration of NA was significantly decreased both in the focus side (9.02 +/- 2.00 mM) and in the nonfocus side (8.88 +/- 2.09 mM) of the patients compared with the controls (10.76 +/- 1.86 mM), in particular if the children had a history of generalized tonic-clonic seizures. The mean concentrations of Cho, Cr, and mI did not differ significantly between the patients and controls. Moreover, the mean hippocampal volume of the focus side of patients was significantly reduced compared with that of the controls.

CONCLUSIONS

Metabolic changes in hippocampi were detected in children with nonsymptomatic localization-related epilepsy and infrequent seizures. Reduced NA could reflect neuronal metabolic dysfunction and/or neuronal damage, as indicated by our volumetric findings.

The GABBR1 locus and the G1465A variant is not associated with temporal lobe epilepsy preceded by febrile seizures

BACKGROUND

Polymorphism G1465A in the GABBR1 gene has been suggested as a risk factor for non-lesional temporal lobe epilepsy (TLE); however, this genetic association study has not been independently replicated. We attempted to replicate this study in our cohort of patients with TLE. Furthermore, we also analyzed the coding sequence of this gene and searched for disease-causing mutations.

METHODS

We included 120 unrelated individuals with TLE that was preceded by febrile seizures (FS) who did not have any evidence of structural lesions suggesting secondary epilepsy. 66 individuals had positive family history of TLE epilepsy and 54 were sporadic. Each patient was genotyped for the presence of G1465A polymorphism. All exons of the GABBR1 gene were screened by single strand confirmation polymorphism method. Genotypes were compared with two independent matched control groups.

RESULTS

We detected two A alleles of the G1465A polymorphism in one homozygous control subject (0.87% of all alleles) and one A allele in a patient with TLE (0.45%, not significant). Other detected polymorphisms in coding regions had similar frequencies in epilepsy patients and control groups. No disease causing mutations in the GABBR1 gene were detected in patients with sporadic or familial TLE.

CONCLUSION

Our results indicate that TLE preceded by FS is not associated with the polymorphisms or mutations in the GABBR1 gene, including the G1465A polymorphism. The proportion of TLE patients with FS in the original study, reporting this positive association, did not differ between allele A negative and positive cases. Thus, our failure to reproduce this result is likely applicable to all non-lesional TLE epilepsies.

Genetic influence on the clinical characteristics and outcome of febrile seizures--a retrospective study

PURPOSE

To assess the influence of the family history (FH) of epilepsy or febrile seizures (FSs) on the clinical presentation of FSs and on their outcome.

METHODS

We reviewed the charts of 482 children admitted to the Ste-Justine Hospital with FSs between 3 months and 6 years of age and followed for at least 5 years.

RESULTS

Children with a positive FH of epilepsy (n=67) showed significantly more focal and recurrent FSs than those without such a FH. The risk of developing partial epilepsy (n=17) or generalized epilepsy (n=19) was significantly greater in children with focal or recurrent FSs, respectively. In children with focal FSs, only two out of 30 (6.7%) children with a negative FH of epilepsy developed partial epilepsy compared with four out of nine (44.4%) children with a positive FH. In children with recurrent FSs, as much as seven out of 34 (20.6%) children with a positive FH of epilepsy developed generalized epilepsy compared to only eight out of 161 (0.05%) of those with a negative FH. Nevertheless, when not taking into account the clinical presentation of FSs, the positive FH of epilepsy constituted a risk factor for developing generalized but not partial epilepsy. Finally, children with a positive FH of FSs (n=120) exhibited significantly more recurrent FSs than those without such a FH, but this did not modify the risk of epilepsy.

CONCLUSION

The FH of FSs and/or epilepsy should be taken into account when evaluating the risk of FSs recurrence and of epilepsy.