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Cortical Location of Benign Paroxysmal Rhythms in the Electrocorticogram

Published online by Cambridge University Press:  14 September 2018

Richard S. McLachlan  and
Neda Lubus
Richard S. McLachlan*
Affiliation:
Department of Clinical Neurological Sciences, London Health Sciences Centre, London, ON Canada
Neda Lubus
Affiliation:
Department of Clinical Neurological Sciences, London Health Sciences Centre, London, ON Canada
*
Richard S. McLachlan, Shaikh Khalifa Medical Center, P. O. Box 51900, Abu Dhabi, United Arab Emirates
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Abstract:

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Background:

Six/second spike waves, 14 and 6/second positive spikes and small sharp spikes are apiculate paroxysmal rhythms in the electroencephalogram, thought to be of no diagnostic importance. The cortical origin of these discharges is documented in this report.

Methods:

These waveforms were assessed in recordings from the surface of the cerebral cortex using implanted subdural electrodes in 61 patients monitored for possible epilepsy surgery.

Results:

Eight patients had 6/second spike wave, four had 14 and 6/second positive spikes and 3 had small sharp spikes. The 6/second spike waves were localised to the posterior cingulate gyrus, a more restricted region than would be predicted from scalp recordings and the 14 and 6/second spikes to the posterior mesial temporal cortex. Small sharp spikes were more widely distributed but also predominated in the posterior mesial temporal area. None of the discharges were congruent with the focus of seizure origin and no interaction with other interictal spikes was found.

Conclusions:

These benign paroxysmal rhythms can appear incidentally in the electrocorticograms of patients with focal epilepsy and should not be confused with focal pathological spike activity or considered to be of any value in localizing the seizure focus.

Résumé:

Résumé:Introduction:

Les pointe-ondes à 6 cycles/secondes, les pointes positives à 14 et 6 cycles/seconde et les pointes brèves sont des rythmes paroxystiques apiculés auxquels on n’attribue pas d’importance diagnostique à l’électroencéphalogramme. L’origine corticale de ces décharges est documentée dans cet article.

Méthodes:

Ces ondes ont été évaluées lors d’enregistrements faits à la surface du cortex cérébral au moyen d’électrodes sous-durales implantées chez 61 patients sous observation en vue d’une chirurgie de l’épilepsie.

Résultats:

Huit patients avaient des pointe-ondes à 6 cycles/seconde, 4 avaient des pointes positives à 14 et 6 cycles/seconde et 3 avaient des pointes brèves. Les pointeondes à 6 cycles/seconde ont été localisées à la circonvolution postérieure du corps calleux, une région plus restreinte que celle prédite à partir des enregistrements de surface, et les pointes à 14 et 6 cycles/seconde au cortex temporal mésial postérieur. Aucune des décharges n’était congruente avec le foyer d’origine de la crise et aucune interaction avec d’autres pointes interictales n’a été observée.

Conclusions:

Ces rythmes paroxystiques bénins peuvent apparaître accessoirement à l’électrocorticogramme de patients présentant une épilepsie focale et ne devraient pas être confondus avec une activité de pointes pathologiques focales ou considérés comme un élément de localisation valable d’un foyer épileptique.

Type
Original Article
Information
Canadian Journal of Neurological Sciences , Volume 29 , Issue 2 , May 2002 , pp. 154 - 158
Copyright
Copyright © Canadian Neurological Sciences Federation 2002

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