Abstracts

Not infrequently, the breach rhythm may be mistaken for potentially epileptogenic activity by the visual EEG analysis. We performed linear and non-linear EEG analysis on the data from the patients who had experienced a craniectomy for hematoma evacuation to elucidate the findings indicating a hemisphere of seizure origin.
The resting scalp EEG under eyes closed, artifact-rejected state from sixteen patients were analyzed. There were six patients who have experienced more than four epileptic seizures after craniectomy (group A) and 10 patients without epileptic seizure (group B). From two adjacent lead positions over the centro-temporal area ipsilateral to the skull defect, we calculated the correlation dimension (D2), the Lyapunov exponent (L1) and the temporal linear mode of complexity (TLMC) as well as relative spectral power of delta (0.5-4Hz), theta (4-8Hz), alpha (8-13Hz) and beta (13-30Hz) components.
There were no significant difference on the L1, TLMC, and relative spectral power of all frequency bands between two groups. But, the EEG of group A showed significantly lower D2 than that of group B (p=0.031), indicating a decreased complexity of the non-linear dynamics in the epileptogenic cerebral hemisphere.
Our results shows that non-linear component, especially D2, of breach rhythm can disclose the epileptogenic regions which cannot be detected by visual or linear analysis of EEG. The non-linear analysis of EEG may be a valuable additional non-invasive method in the predicting the occurrence of poststroke seizure or the prognosis of partial seizure disorders arising near the skull defect.