Audit of EEG Reporting Temporal Abnormalities

Abstract

The electroencephalogram (EEG) is a valuable neurodiagnostic tool in the evaluation of patients suspected of having epilepsy. A normal EEG does not necessarily exclude epilepsy but the detection of epileptiform abnormalities (such as spikes, sharp waves and spike-slow-wave discharges) indicates a seizure tendency which may support the clinical diagnosis of epilepsy and provide additional information regarding seizure type and focus.Unfortunately, there is often considerable diversity among clinicians in the interpretation of tracings. Spikes, sharp waves or spike-slow-wave discharges are sometimes difficult to identify correctly. The disagreement regarding spike detection ABSTRACT: Background: To ensure the overall quality of our electroencephalogram (EEG) laboratory, we decided to perform an audit of EEGs interpreted at our institution, focusing initially on EEGs reporting temporal abnormalities. Methods: Reports of all EEGs performed between January 1st and June 30th, 2006 were reviewed in order to identify tracings mentioning abnormalities in the temporal regions. These records were then independently reviewed by two epileptologists on two distinct occasions, separated by an interval of at least six months. If the recording was considered normal after this process, the cause for misinterpretation was identified and the patient's chart was reviewed to determine if he was epileptic or not based on available evidence until June 2009. Results: In the first half of 2006, 143 out of 773 EEGs mentioned temporal abnormalities (18.5%). In general, intra-and interrater agreement ratios between our two epileptologists were moderate to substantial for normality, presence of epileptic activity and presence of slowing. Forty-five recordings (31.5%) were reported as normal independently by them on two distinct sittings six months apart. The most common causes for misinterpretation were the presence of benign epileptiform variants, normal sharply contoured patterns of somnolence or hyperventilation. Chart review confirmed that most were non-epileptic patients (60% non-epileptic, 27% epileptic, 13% unknown). Conclusion: Moderate to substantial intra-and interrater agreement as well as frequent misinterpretation of physiological variants indicate that some corrective measures need to be implemented to improve the consistency of EEG interpretation amongst our group of electroencephalographers. RÉSUMÉ: Vérification de la notification d'anomalies temporales à l'EEG.Contexte : Nous avons décidé de procéder à la vérification des EEG interprétés à notre institution afin de nous assurer de la qualité globale de notre laboratoire d'EEG, en ciblant initialement les EEG qui rapportaient des anomalies temporales. Méthodologie : Tous les rapports d'EEG effectués entre le premier janvier et le 30 juin 2006 ont été révisés pour identifier les tracés mentionnant des anomalies dans les régions temporales. Ces dossiers ont ensuite été révisés par deux épileptologues à deux reprises, à six mois d'intervalle. Si l'enregistrement était considéré ...

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