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Triphasic Waves Versus Nonconvulsive Status Epilepticus: EEG Distinction

Published online by Cambridge University Press:  02 December 2014

Jean-Martin Boulanger ,
Charles Deacon ,
Diane Lécuyer ,
Sylvie Gosselin  and
Jean Reiher
Jean-Martin Boulanger
Affiliation:
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada
Charles Deacon*
Affiliation:
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada
Diane Lécuyer
Affiliation:
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada
Sylvie Gosselin
Affiliation:
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada
Jean Reiher
Affiliation:
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, Quebec, Canada
*
Department of Neurology, Centre Hospitalier Universitaire de Sherbrooke, 3001 12th Avenue North, Sherbrooke, Quebec, J1H 5N4, Canada.
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Abstract:

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Background:

Triphasic waves (TWs) and generalized nonconvulsive status epilepticus (GNCSE) share morphological features that may create diagnostic ambiguity.

Objective::

To describe electroencephalographic differences between TWs and GNCSE.

Methods:

We retrospectively compared the electroencephalograms (EEGs) of two groups of patients presenting with decreased level of consciousness; those with TWs associated with metabolic encephalopathy and those with GNCSE. We studied the following: demographics, etiology and EEG morphological features. All EEGs were classified blindly (TWs or GNCSE) by two expert EEGers. Agreement between experts and concordance with clinical diagnosis were measured.

Results:

We analysed 87 EEGs (71 patients) with TWs and 27 EEGs (13 patients) with GNCSE. Agreement between experts and concordance with clinical diagnosis were excellent. When compared to TWs, epileptiform discharges associated with GNCSE had a higher frequency (mean=2.4Hz vs 1.8Hz) (p<0.001), a shorter duration of phase one (p=0.001), extra-spikes components (69% vs 0%) (p<0.001) and less generalized background slowing (15.1% vs 91.1%) (p<0.001). Amplitude predominance of phase two was common with TWs (40.8% vs 0%) (p=0.01). Lag of phase two was absent in all cases of GNCSE but present in 40.8% of patients with TWs. Noxious or auditory stimulation frequently increased the TWs (51%) while it had no effect on the epileptiform pattern (p=0.008).

Conclusion:

Certain EEG morphological criteria and the response to stimulation are very helpful in distinguishing TWs from GNCSE.

Résumé:

RÉSUMÉ:Introduction:

Les ondes triphasiques (OT) et le status épileptique généralisé nonconvulsif (SEGNC) peuvent être difficiles à distinguer sur l'EEG.

Méthode:

Nous avons analysé rétrospectivement les EEGs de deux groupes de patients: ceux avec OT dans un contexte d'encéphalopathie métabolique et ceux avec SEGNC. Tous les patients avaient une altération de la conscience. Les caractéristiques suivantes furent analysées: âge, étiologie sous-jacente et plusieurs caractéristiques morphologiques de l'EEG. Tous les EEGs ont été classifiés à l'aveugle (OT ou SEGNC) par deux électroencéphalographistes experts et l'exactitude par rapport au diagnostic clinique a été évaluée de même que la concordance entre les deux experts.

Résultats:

87 EEGs (71 patients) avec OT et 27 EEGs (13 patients) avec SEGNC ont été analysés. La concordance entre les experts et l'exactitude de l'interprétation par rapport au diagnostic clinique étaient excellentes. Par rapport aux OT, les décharges épileptiformes associées au SEGNC avaient: une fréquence plus élevée (2,4 Hz vs 1,8Hz) (p<0.001), une phase 1 de plus courte durée (p=0.001), des polypointes associées aux décharges (69% vs 0%) (p<0.001) et moins de ralentissement généralisé des rythmes de fond (15,1% vs 91,1%) (p<0.001). La prédominance d'amplitude de la phase 2 était fréquente avec les OT (40,8 % vs 0%) (p=0.01) de même qu'un délai de la phase 2 (40,8% vs 0%). La stimulation douloureuse ou auditive causait une augmentation des OT (51%) alors qu'elle n'avait aucun effet sur les anomalies épileptiformes.

Conclusion:

Certaines caractéristiques électrographiques morphologiques et l'effet de la stimulation sont très utiles pour distinguer les OT des anomalies épileptiformes du SEGNC.

Type
Original Articles
Information
Canadian Journal of Neurological Sciences , Volume 33 , Issue 2 , May 2006 , pp. 175 - 180
Copyright
Copyright © The Canadian Journal of Neurological 2006

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