ELECTROGRAPHIC VARIATION OF SEIZURES ARISING FROM THE SAME ICTAL ZONE IN PATIENTS WITH MULTIFOCAL EPILEPSY
Abstract number :
2.082
Submission category :
Year :
2002
Submission ID :
3291
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Kevin M. Rathke, Barbara Schauble, Elson L. So. Neurology, Mayo Clinic, Rochester, MN; Neurology, Mayo Clinic, Rochester, MN; Neurology, Mayo Clinic, Rochester, MN
RATIONALE: We have previously shown that in patients with multifocal epilepsy seizures arising from the same ictal zone (as determined by intracranial EEG) often have dissimilar clinical semiologies (Neurology:58(6)(Suppl 2), p. 40, 2002) and hypothesize that there may be more than one focus for generating electrographic seizures within a single ictal zone.
METHODS: We performed blinded reviews of the intracranial EEGs of 17 multifocal epilepsy patients. Two seizures arising from the same ictal zone were reviewed in each patient (total of 34 seizures reviewed). Video and EEG recordings were reviewed separately and blinded from each other, and without prior knowledge of the clinical history or neuroimaging findings. The morphology of EEG discharge at seizure onset was compared between pairs of seizures with dissimilar and pairs with similar semiology.
RESULTS: Seizures in thirteen of the 17 patients (76.5%) had dissimilar semiology. Seizures in the other four patients (23.5%) were similar in semiology. EEG discharge morphology at seizure onset was different in 7/13 patients (54%) whose seizures were dissimilar in semiology despite the same intracranial ictal zone localization. In contrast, morphology of the EEG discharge was the same in all patients whose seizures were similar in semiology. In the 13 patients with dissimilar seizure semiology, differences observed in their EEG discharge morphology could be divided into the following four categories: (I) rhythmic beta discharge in one seizure and 3 to 5 Hz spike-waves in the other seizures (4 patients); (II) rhythmic beta discharge in one seizure and rhythmic theta discharge in the other seizure (1 patient); (III) rhythmic beta discharge/electrodecrement in one seizure and electrodecrement only in the other seizure (in 1 patient); (IV) electrodecrement in one seizure and 4 Hz spike-wave in the other seizure (in 1 patient).
CONCLUSIONS: Our study suggests that subpopulations of seizure foci may exist within a single ictal zone in patients with multifocal epilepsy. The findings may explain our initial observation that seizures arising from the same ictal zone can have dissimilar semiology.
[Supported by: Mayo Foundation for Research and Education]