Transitional sharp waves at ictal onset--a neocortical ictal pattern.

Azar NJ, Lagrange AH, Abou-Khalil BW
Clin Neurophysiol. 2009 120 (4): 665-72

PMID: 19264545 · DOI:10.1016/j.clinph.2009.01.010

OBJECTIVE - Some seizures are characterized by a transitional sharp wave (TShW) at ictal onset. We evaluated the clinical significance and localizing value of TShW in partial-onset seizures.

METHODS - We identified and analyzed all scalp ictal recordings with a TShW at ictal onset in the Vanderbilt Epilepsy Monitoring Unit over a period of 12 months.

RESULTS - A total of 52 ictal discharges in 13 patients started with a TShW. The center of TShW field was concordant with the final localization/lateralization, while that of the subsequent ictal discharge was concordant in only 6 patients. The subsequent rhythmic ictal discharge was non-localizing in 4 patients and misleading in the remaining 3 patients. The final localization was neocortical temporal or frontal in 11 patients, occipito-parietal in one, and undetermined in 1 patient. None of 61 ictal discharges in 15 patients with mesial temporal lobe epilepsy studied in the same time period started with a TShW.

CONCLUSION - In this patient series, the TShW was a marker of neocortical seizure onset. The TShW field provided more accurate localization or lateralization of the ictal focus than the following rhythmic ictal discharge.

SIGNIFICANCE - TShW at seizure onset should suggest a neocortical rather than hippocampal seizure onset.

MeSH Terms (15)

Adolescent Adult Brain Mapping Electroencephalography Epilepsies, Partial Female Humans Magnetic Resonance Imaging Male Middle Aged Neocortex Retrospective Studies Signal Processing, Computer-Assisted Tomography, Emission-Computed, Single-Photon Young Adult

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