Abstracts

Rationale: The hypothesis was tested that secondary generalized seizures (SGS) are not truly generalized and may involve selective cortical regions. Methods: The spread from focal to generalized seizures was studied in 20 SGS in 15 surgery candidates. Electrode contacts were assigned the following regions: frontal inferior/fronto-orbital; prefrontal lateral; anterior cingulate; temporal lateral; the hippocampus; the amygdala; the insula, the basal ganglia, and the SMA. A behavioural analysis of the ictal video-recordings was performed by two independent readers in order to ascertain the onset of the SGS. The SGS onset was designated as the moment when the seizure clearly involved the whole body, including the head, face, and all limbs. The EEG recordings were then analyzed and evaluated using the rating scale developed by Blumenfeld et al (2003). Positive ratings were assigned to ictal EEG patterns; negative ratings were assigned to patterns resembling interictal slowing. The seizure ratings in each region were compared with the seizure rating in the hippocampus. The Kruskal-Wallis ANOVA test followed by the Mann-Whitney U test were used. Results: The ranking significantly differed in the cingulate and fronto-orbital cortex; moreover a trend to significance appeared in the lateral prefrontal cortex. In these regions, the slow activity dominated. It was interesting to note that the slow waves appeared mainly in regions that are critical for regulation of the thalamocortical circuitries. At variance with SGS, in absence seizures, the orbital, dorsolateral and medial frontal cortices are associated with spiking at seizure onset (Holmes et al 2004). This may indicate a substantial difference between the mechanisms of seizure spread in primary and secondary generalized seizures. Conclusions: Conclusion: Our data suggest that the secondary generalization involves selective cortical networks. The beginning of SGS does not implicate global cortical involvement. Supported by MSMT CR Research Project: MSM0021622404