EEG bei Kindern mit komplizierten Fieberkrämpfen
Abstract
Background
This is an updated version of original Cochrane review published in Issue 1, 2014.
Febrile seizures can be classified as simple or complex. Complex febrile seizures are associated with fever that lasts longer than 15 minutes, occur more than once within 24 hours and are confined to one side of the child's body. It is common in some countries for doctors to recommend an electroencephalograph (EEG) for children with complex febrile seizures. A limited evidence base is available to support the use of EEG and its timing after complex febrile seizures among children.
Objectives
To assess the use of EEG and its timing after complex febrile seizures in children younger than five years of age.
Search methods
For the latest update of this review, we searched the Cochrane Epilepsy Group Specialized Register (6 July 2015), the Cochrane Central Register of Controlled Trials (CENTRAL, 2005, Issue 6), MEDLINE (6 July 2015) and ClinicalTrials.gov (6 July 2015). We applied no language restrictions.
Selection criteria
All randomised controlled trials (RCTs) that examined the utility of an EEG and its timing after complex febrile seizures in children.
Data collection and analysis
Review authors selected and retrieved the articles and independently assessed which articles should be included. We resolved disagreements by discussion and by consultation with the Cochrane Epilepsy Group. We applied standard methodological procedures expected by Cochrane.
Main results
Of 37 potentially eligible studies, no RCTs met the inclusion criteria.
Authors' conclusions
We found no RCTs as evidence to support or refute the use of EEG and its timing after complex febrile seizures among children. An RCT can be planned in such a way that participants are randomly assigned to the EEG group and to the non‐EEG group with sufficient sample size. Since the last version of this review, we found no new studies.
PICO
Laienverständliche Zusammenfassung
EEG bei Kindern mit komplizierten Fieberkrämpfen
Hintergrund
Es wird zwischen einfachen und komplizierten Fieberkrämpfen unterschieden. Komplizierte Fieberkrämpfe gehen mit erhöhter Temperatur (Fieber) einher und dauern mehr als 15 Minuten, treten mehrfach innerhalb von 24 Stunden auf und betreffen nur einen Teil des Körpers. In einigen Ländern empfehlen Ärzte für Kinder mit komplizierten Fieberkrämpfen routinemäßig die Durchführung einer Elektroenzephalografie (EEG), bei der die elektrische Aktivität des Gehirns aufgezeichnet wird. Die EEG könnte dabei helfen, die Ursachen der Krämpfe zu identifizieren und das Risiko künftiger Fieberkrämpfe vorherzusagen.
Studienmerkmale
Wir durchsuchten die wissenschaftlichen Datenbanken nach randomisierten kontrollierten Studien (klinische Studien, in denen Menschen nach dem Zufallsprinzip einer von zwei oder mehr Behandlungsgruppen zugeteilt werden; diese Prinzipien gelten als „Goldstandard“ des Studiendesigns), in denen Kinder unter fünf Jahren mit einem ersten komplizierten Fieberkrampf in Bezug auf die folgenden diagnostischen Unterschiede miteinander verglichen wurden: Durchführung einer EEG, keine Durchführung einer EEG oder verzögerte Durchführung einer EEG (nach einem zweiten Fieberkrampf). Wir wollten uns die Anzahl der Fieberkrämpfe ansehen, die einen, zwei, 12 und 24 Monate nach der EEG auftraten.
Hauptergebnisse und Qualität der Evidenz
Trotz unserer Recherche in allen möglichen Quellen konnten wir keine randomisierten kontrollierten Studien zu dieser Fragestellung bis zum 6. Juli 2015 finden. Daraus schlossen wir, dass es keine Evidenz von hoher Qualität dazu gibt, ob nach komplizierten Fieberkrämpfen bei Kindern eine EEG durchgeführt werden sollte oder nicht, und wann dies erfolgen sollte. Deshalb werden gut konzipierte, randomisierte kontrollierte Studien benötigt. Wir haben die Absicht, diesen Review regelmäßig zu aktualisieren und hoffen, dass künftig neue randomisierte Studien zu dieser Fragestellung durchgeführt werden.
Authors' conclusions
Background
Description of the condition
This review is an update of a previously published review in The Cochrane Database of Systematic Reviews (2014, Issue 1) on 'EEG for children with complex febrile seizures'.
According to the National Institutes of Health (NIH) and the International League Against Epilepsy (ILAE), febrile seizures can occur between the ages of one month and five years (Freeman 1980; ILAE 1993), and are associated with fever with no intracranial infection or defined cause (Freeman 1980). Febrile seizures can be classified as simple or complex. Simple febrile seizures are generalised tonic or tonic‐clonic convulsions lasting less than 15 minutes that occur only once in a 24‐hour period in a neurologically and developmentally normal child. If focal features are present, the seizures last longer than 15 minutes, the child has a pre‐existing neurological condition and the seizures occur multiple times (recurrent within 24 hours) or within the same febrile event, the febrile seizures are referred to as complex (Francis 2006; Kevin 2001; Kliegman 1996; Waruiru 2004). The incidence of febrile seizures varies from 2% to 5% in Western Europe and the US (Joshi 2005; Waruiru 2004), from 5% to 10% in India and is reported at 8.8% in Japan and 14% in Guam (Waruiru 2004). Data from the low‐to middle income countries are limited (Waruiru 2004).
A child with febrile seizures usually does not need to be hospitalised. However, when the seizure is prolonged or is accompanied by a serious infection, or when the source of the infection cannot be determined, hospitalisation for observation may be recommended. Prolonged daily use of oral antiepileptic drugs to prevent febrile seizures is usually not recommended because of their potential for adverse effects and their questionable effectiveness in preventing such seizures (Kliegman 1996; Offringa 2012).
Description of the intervention
An electroencephalograph (EEG) records brain waves detected by electrodes placed on the scalp. Reporting of paroxysmal EEG abnormalities in children with febrile seizures may vary widely (Panayiotopoulos 2005). The reasons may be related to differences in participant selection by different authors, the criteria used in different studies to define paroxysmal discharges or the timing of the EEG.
The American Academy of Pediatrics practice parameter on febrile seizures recommends that an EEG should not be part of a routine investigation after a simple febrile seizure in neurologically normal children because of its lack of usefulness in predicting recurrence risk or future epilepsy (American Academy of Pediatrics 1996; Joshi 2005; Kuturec 1997). The quality standards subcommittees of the American Academy of Neurology, the Child Neurology Society and the American Epilepsy Society recommend an EEG in the initial evaluation of the first afebrile seizure, as an abnormal EEG predicts recurrence (Hirtz 2000; Joshi 2005). The precise role of EEG in the evaluation of children with complex febrile seizure has not been established; however, it is common for both paediatricians and specialists to recommend EEGs on these children in some countries (Joshi 2005; Millichap 1991). An EEG taken within the first week after a febrile seizure is termed an 'early EEG', whereas an EEG taken anytime between the first week and one month after the seizure activity is termed a 'late EEG'. Few retrospective studies have tried to assess the use of EEGs in complex febrile seizure (Maytal 2000; Yucel 2004).
How the intervention might work
An EEG performed in the evaluation of complex febrile seizures may help identify the nature of the underlying acute or remote cerebral pathology and predict the risk of future seizures.
Why it is important to do this review
Much uncertainty remains about the use of an EEG and its timing in children with complex febrile seizures, hence it is necessary to carry out this review. This is an update of previously published review in The Cochrane Database of Systematic Review published in 2014, which found no evidence to support or refute the use of EEG for children with complex febrile seizures.
Objectives
To assess the use of EEG and its timing after complex febrile seizures in children younger than five years of age.
Methods
Criteria for considering studies for this review
Types of studies
We planned to include parallel‐group randomised controlled trials (RCTs).
Types of participants
Participants in the studies eligible for inclusion were children of either sex younger than five years of age with a first episode of complex febrile seizure.
Participants would be included in the review only:
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if the EEG was performed after the first complex febrile seizure episode; or
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if recruitment of participants into the study was delayed and the EEG was performed before the participant's second seizure.
We excluded studies in which children had other neurological disorders (e.g. behavioural disorders, cerebral palsy, mental retardation).
Types of interventions
The intervention was EEG investigation. We selected two comparisons.
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Children without administration of an EEG versus children with administration of an EEG (early or late or at any time).
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Children with administration of an early EEG versus children with administration of a late EEG.
Types of outcome measures
Primary outcomes
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Proportions of children developing seizures of any type after follow‐up periods of one month, six months, 12 months and two years in two comparison groups of EEG versus no EEG and early EEG versus late EEG.
We decided to include any type of seizure in the outcome. We recorded the available outcome measures with respect to a particular time period. In addition, we planned to contact the original trial authors to enquire whether outcome measurements had been recorded for other time periods of interest. We believe that the most important clinically relevant time period was two years.
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Risk of recurrence between no EEG and EEG (early EEG, late EEG or any other time), which will act as a surrogate outcome.
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Total number of seizure episodes in each group during two‐year follow‐up.
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Time to development of seizures as time to event outcome.
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Adverse events (although the EEG may not cause any adverse event per se, adverse events may be related to sedation given to children and may be transient).
Search methods for identification of studies
Electronic searches
Searches were run for the original review on 18 October 2012, and subsequent searches were run on 17 October 2013 and 6 July 2015. For the latest update, we searched the following databases using the search strategies shown in Appendix 1.
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The Cochrane Epilepsy Group Specialized Register (6 July 2015).
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The Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 6).
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MEDLINE (Ovid, 1946 to 6 July 2015).
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ClinicalTrials.gov (6 July 2015).
Searching other resources
We searched the references of all studies retrieved in full to identify additional research papers. We contacted authors of relevant articles and experts in the field to ask about additional research papers and unpublished trials. We looked for conference proceedings for trials relevant to our review. We decided not to impose language restrictions.
Data collection and analysis
Selection of studies
Two review authors (PBS (methodology expert), SJ (content expert)) carried out the searches (Lefebvre 2011), and independently carried out an initial screening of the titles of research papers. If papers were potentially relevant, the review authors independently screened the abstracts. We retrieved the full text for all articles whose abstracts were relevant. When full‐text articles were not available, we contacted the study authors and asked them to provide the full text of the article. We decided to use this search methodology during screening of the cross‐references of the full‐text retrieved articles and articles suggested by authors and experts in the field. Two review authors (PBS, SJ) independently reviewed the full‐text articles and classified each into one of the following groups.
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Included studies.
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Excluded studies.
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Studies pending decision (if required, we contacted study authors to request additional details of the study).
We recorded the information on the eligibility assessment form included in Appendix 2.
We attempted to identify duplicate publications by assessing similar study types, same place or same authors (maybe with different sequence). We used reference management software (Mozilla with Zotero) to identify and exclude duplicate publications. In cases of doubt, we contacted the study authors to avoid inclusion of duplicate publications in this review.
We agreed to resolve any disagreements by discussion and to reach a final decision by consensus or by consultation with the Cochrane Epilepsy Group. We used standard methodological procedures expected by Cochrane.
Data extraction and management
We could not extract the data in the present review, as no study met the inclusion criteria. We planned to conduct the data extraction process as follows.
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Two review authors (PBS, SJ) planned to extract required data from the full‐text articles of the included studies independently. (We have included the data extraction form in Appendix 3.) The data extraction form had five components.
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Identification of study.
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Characteristics of included studies with a brief description in tabular form of methods, participants, interventions and outcomes, and notes on specific issues (if any).
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'Risk of bias' table, as per guidelines of the Cochrane Handbook for Systematic Reviews of Interventions (Altman 2011).
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Measurements of treatment effects extracted.
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Information pertaining to any discrepancy noted in records of the clinical trial registry.
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We agreed to resolve any disagreements by discussion and to reach a final decision by consensus or by consultation with the Cochrane Epilepsy Group. We agreed to follow guidelines of a quality of reporting meta‐analysis, or QUOROM statement, and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (formerly QUOROM) (Moher 2009).
Assessment of risk of bias in included studies
We could not assess the risk of bias in the present review, as no study met the inclusion criteria.
We wanted to report the following bias as recommended in the Cochrane Handbook for Systematic Reviews of Interventions for 'Risk of bias' tables (Altman 2011; Appendix 4). We agreed to fill the description for each domain with the quote from the article or correspondence and then comment with judgement regarding particular bias (yes, no or unclear); we planned to undertake a summary assessment of risk of bias for each outcome (across domains) within and across studies and to make judgements about the risk of bias as low, unclear or high. We planned to report a risk of bias graph and a risk of bias summary figure. Two review authors (PBS, SJ) intended to assess the risk of bias independently. We agreed to resolve any disagreements by discussion and to reach a final decision by consensus or by consultation with the Cochrane Epilepsy Group.
We provided a list of excluded studies with reasons for exclusion in tabular form (see Characteristics of excluded studies table).
We planned to report in tabular form the details of any ongoing studies in terms of methods, interventions and outcomes or trial registration numbers; however, we found no ongoing studies.
Measures of treatment effect
We could not measure the treatment effect in the present review, as no study met the inclusion criteria. We planned to measure treatment effect as follows.
We planned to calculate the proportions of children developing seizures after follow‐up periods of one month, six months, 12 months and two years. We also planned to calculate risk of recurrence between no EEG and EEG (early EEG, late EEG or any other time), total number of seizure episodes in each group during the two‐year follow‐up, time to development of seizures as time to event outcome and adverse events (if any). We agreed to use odds ratio for dichotomous outcomes and mean difference for continuous data. We decided to convert extracted data to the above measures for treatment effects, if they were given in other forms. We planned to extract or calculate 95% confidence intervals for all data. In the case of insufficient information, we intended to contact study authors to ask for additional details.
Unit of analysis issues
We did not anticipate any unit of analysis issues.
Dealing with missing data
We contacted study authors to ask for missing data such as method of randomisation not stated in the paper or whether the outcome of interest was not reported but had been analysed. The reasons for missing data if found would have helped us with imputation of missing data.
Assessment of heterogeneity
We could not assess the heterogeneity in the present review, as no study met the inclusion criteria. We planned to assess heterogeneity as follows.
We planned to assess clinical heterogeneity by comparing participant factors, interventional factors, outcome factors and methodological heterogeneity by study methods. We also planned to assess statistical heterogeneity by measuring variability in interventional effects by visually comparing the overlap of confidence intervals on forest plots. If confidence intervals for the results of individual studies had poor overlap, this might have indicated the presence of statistical heterogeneity. We also planned to measure statistical heterogeneity using the I2 statistic and interpreting it as follows (Deeks 2011).
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0% to 40%: might not be important.
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30% to 60%: may represent moderate heterogeneity.
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50% to 90%: may represent substantial heterogeneity.
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75% to 100%: might represent considerable heterogeneity.
Assessment of reporting biases
During this stage, the review authors planned to determine primary and secondary outcomes of the included studies from clinical trial registries (if possible) to assess any discrepancy in reporting. If we found any, we planned to report them. We agreed to assess funnel plot asymmetry if we identified more than 10 studies. Reasons for asymmetry include publication bias, outcome reporting bias and heterogeneity.
Data synthesis
We could not attempt data synthesis in the present review, as no study met the inclusion criteria. We planned to perform data synthesis as follows.
We planned to analyse each trial and record data on the data extraction form. Review authors intended to enter the results of each study independently using Review Manager 5 (RevMan 2014). We planned to carry out a meta‐analysis according to Cochrane guidelines (Higgins 2011); the most common method available using Review Manager 5 is the Mantel‐Haenszel method. If RCTs were clustered, we would have used the inverse method. In case of heterogeneity, we planned to carry out a thorough assessment (see Assessment of heterogeneity).
Subgroup analysis and investigation of heterogeneity
We could not attempt the above in the present review, as no study met the inclusion criteria. The process agreed upon was as follows.
We planned to carry out subgroup analyses based on sex, duration of disease, duration of hospitalisation and length of follow‐up. In cases of significant heterogeneity, we might have followed the steps outlined below.
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Recheck extraction and recording of data.
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Change from random‐effects model to fixed‐effect model.
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Perform sensitivity analysis (see Sensitivity analysis).
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Explore heterogeneity by subgroup analysis.
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Present systematic review without meta‐analysis.
Sensitivity analysis
Sensitivity analysis is a repeat primary analysis in which alternative decisions and ranges of values are substituted for decision making related to assessment of the robustness of conclusions.
We could not attempt sensitivity analysis in the present review, as no study met the inclusion criteria.
We planned to carry out the following steps in a sensitivity analysis.
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Some studies have larger effects than others because:
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random error means that multiple replications of the same study will produce different effect estimates because of sampling variation, even if replications would yield the right answer on average. The results of smaller studies are subject to greater sampling variation and hence are less precise. Imprecision is reflected in the confidence interval around the intervention effect estimate from each study and in the weight given to the results of each study in a meta‐analysis. More precise results are given more weight.
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In cases of missing values, use of following imputation methods are suggested:
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many methods for imputation techniques have been proposed. In cases of dichotomous data, best case‐worst case analysis is performed, so it is possible to find out how the risk factor or the result value may vary in different situations. For continuous data, the last value takes the role of the missing value. These imputations are important because RCTs have to be analysed as intention‐to‐treat analyses.
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Use the random‐effects model instead of the fixed‐effect model.
The above sensitivity analyses were pre‐specified, but it was not possible to specify all sensitivity analyses, as many potential issues might develop only in the course of completing the review. In case sensitivity analysis had an influence on the robustness of the conclusion, we planned to attempt to resolve the uncertainty by contacting trial authors and consulting the Cochrane Epilepsy Group. As it might not be possible to report all sensitivity analyses in detail, we planned to provide a summary table. Sensitivity analysis would have helped us to explore the influence of various factors.
'Summary of findings' tables
We planned to provide 'Summary of findings' tables, prepared with the help of GRADEpro software (GRADEpro 2014). We planned to report a rating of overall quality of evidence for each outcome, as well as conclusions, and implications for practice and research (Appendix 5). Two review authors (PBS, SJ) agreed to prepare the 'Summary of findings' tables independently. We agreed to resolve any disagreements by discussion and to reach final decisions by consensus or by consultation with the Cochrane Epilepsy Group.
We conducted the review according to the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).
Results
Description of studies
Results of the search
With the help of the Trials Search Co‐ordinator of the Cochrane Epilepsy Group, the search identified 37 potentially eligible studies. The summary of the results of the search is included in Appendix 6. For this update, literature searches identified four studies. After assessing the titles and abstracts, the review authors excluded all 37 studies; therefore, no studies were eligible for inclusion in the review (see Characteristics of excluded studies table).
Included studies
None of the studies met the inclusion criteria; thus, we did not include any study in the present review.
Excluded studies
We excluded all 37 studies because the study design and the intervention were not of interest for this review (see Excluded studies; Characteristics of excluded studies table).
Risk of bias in included studies
We included no studies in this review, hence, the risk of bias is not applicable.
Effects of interventions
In the absence of any suitable studies for this review, analyses were not possible. Although we could not attempt data collection and analysis as was decided in the protocol, we decided to describe the process of different aspects of data collection and analysis, as the review will be updated regularly and the full protocol may not be easily accessible to all users of this evidence.
We could provide no 'Summary of findings' table in the present review, as no study met the inclusion criteria.
Discussion
Summary of main results
We did not find any RCTs of EEG for children with complex febrile seizures. Hence, currently no randomised high‐quality evidence can be reported for an EEG and its timing after complex febrile seizures in children younger than five years of age.
Overall completeness and applicability of evidence
We performed a comprehensive search of the literature as described in Appendix 6, and assessed 37 studies that may have been relevant to the review. We excluded all 37 studies so we identified no RCTs.
Quality of the evidence
We found no studies.
Potential biases in the review process
None.
Agreements and disagreements with other studies or reviews
We found no other similar review. However, a few published non‐randomised studies to date have looked specifically at complex febrile seizures and the role of EEG in its evaluation (Joshi 2005; Maytal 2000; Yucel 2004). In one retrospective review of 33 neurologically normal children with EEGs within one week of complex febrile seizures, Maytal et al. found none with abnormalities, but Yucel et al. reported abnormalities in 71 of 159 children with complex febrile seizures analysed retrospectively over seven years. In the Yucel et al. group, 16 had abnormal EEG records in the first week. Of 71 children with abnormal EEG records, 51 were diagnosed with epilepsy on follow‐up. One other study by Joshi et al. showed that children with complex febrile seizures are approximately 3.5 times more likely to display an abnormal EEG within seven days post ictus in comparison with children with complex febrile seizures in whom the EEG was performed beyond the seven‐day period post ictus. Hence, conflicting reports describe the utility of EEG and its timing after complex febrile seizures among children.
