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EEG Results are Rarely the Same if Repeated within Six Months in Childhood Epilepsy

Published online by Cambridge University Press:  18 September 2015

Peter Camfield ,
Kevin Gordon ,
Carol Camfield ,
John Tibbies ,
Joseph Dooley  and
Bruce Smith
Peter Camfield
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
Kevin Gordon
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
Carol Camfield*
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
John Tibbies
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
Joseph Dooley
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
Bruce Smith
Affiliation:
Department of Pediatrics and Mathematics, Dalhousie University and the IWK Children’s Hospital, Halifax, Nova Scotia
*
IWK Children’s Hospital, Box 3070, Halifax, Nova Scotia, Canada B3J 3G9
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Abstract

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Objective

To assess the reliability of interictal spike discharge in routine electroencephalography (EEG) testing in children.

Method

EEG results of all children diagnosed in Nova Scotia with epilepsy onset between 1977–85 (excluding myoclonic, akinetic-atonic and absence) were reviewed. The results of the EEG at time of diagnosis (EEG1) were compared with those of a second EEG (EEG2) within 6 months.

Results

Of 504 children with epilepsy, 159 had both EEG1 and EEG2. EEG2 was more likely ordered if EEG1 was normal or showed focal slowing but less likely if EEG1 contained sleep (p < 0.05). EEG1 and EEG2 were both normal in 23%. If EEG1 was abnormal, there was a 40–70% discordance for the type of abnormality on EEG2. Abnormalities were present on both EEG1 and EEG2 in 67 cases. Of the 42/67 with major focal abnormalities on EEG1, 7 had only generalized spike wave on EEG2. Of the 17/67 with only generalized spike wave on EEG 1, 7 showed only major focal abnormalities on EEG2. Statistical testing showed low Kappa scores indicating low reliability.

Conclusions

The interictal EEG in childhood epilepsy appears to be an unstable test. A repeat EEG within 6 months of a first EEG may yield different and sometimes conflicting information.

Résumé

Résumé<span class='italic'><span class='bold'>Objectif</span></span>

Le but de l’étude était d’évaluer la fiabilité des décharges de pointes interictales dans les EEGs de routine chez l’enfant.

<span class='italic'><span class='bold'>Méthode</span></span>

Nous avons révisé les EEGs de tous les enfants chez qui on a posé un diagnostic initial d’épilepsie entre 1977 et 1985 (excluant l’épilepsie myoclonique, akinétique-atonique et les absences). Le résultat de l’EEG initial (EEG1) a été comparé à celui du second EEG fait dans les six mois du premier (EEG2).

<span class='italic'><span class='bold'>Résultats</span></span>

Parmi les 504 enfants épileptiques, 159 ont subi les deux examens, l’EEG 1 et PEEG2. L’enfant était plus susceptible d’avoir subi TEEG2 si l’EEG1 était normal ou montrait un ralentissement focal et il était moins probable qu’il l’ait subi si l’EEG1 incluait du sommeil (p < 0.05). Les deux EEGs étaient normaux chez 23% des enfants. Si l’EEG1 était anormal, il y avait une discordance de 40 à 70% quant au type d’anomalie présente à l’EE2. Les deux EEGs étaient anormaux chez 67 cas. Parmi les 42/67 cas dont l’EEG présentait des anomalies focales majeures, 7 avaient seulement des complexes pointe-onde généralisés à TEEG2. Parmi les 17/67 cas dont l’EEG présentait des complexes pointe-onde à l’EEG1, 7 présentaient seulement des anomalies focales majeures à l’EEG2. L’analyse statistique a montré un score de Kappa bas indiquant un faible degré de fiabilité.

<span class='italic'><span class='bold'>Conclusions</span></span>

L’EEG interictal dans l’épilepsie de l’enfant semble être une épreuve instable. Un EEG de contrôle dans les six mois du premier peut fournir une information différente et parfois discordante.

Type
Original Articles
Information
Canadian Journal of Neurological Sciences , Volume 22 , Issue 4 , November 1995 , pp. 297 - 300
Copyright
Copyright © Canadian Neurological Sciences Federation 1995

References

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