Abstracts

RATIONALE: The transition of the brain activity toward an epileptic seizure is still a poorly understood phenomena. Dynamics changes in brain activity have been detected several minutes before the seizure emergence in populations of patients with mesial temporal lobe epilepsy (MTLE), using non-linear analyzes of intracranial EEG recordings. Similar detections of a preictal state were also obtained with standard scalp EEG recordings using a modified non-linear method (The Lancet 2001; 357: 183-88)
METHODS: Here we applied the non-linear similarity analyzis to 41 seizures from 11 patients with refractory partial epilepsy originating from various sites of the neocortex.
RESULTS: 1) A preictal state was detected in 90% of the patients and in 83% of the seizures whatever their localization, with a mean anticipation time of 7.5 minutes. 2) Similar preictal dynamical changes were detected when non-linear analysis methods were applied to either intracranial or to scalp EEG recordings. 3) The recording sites exhibiting these preictal changes were distributed both within the epileptogenic focus and at remote locations. 4) Most preictal dynamics changes were not correlated with linear changes in the frequency spectrum, or changes of visually inspected EEG and patients[ssquote] behavior.
CONCLUSIONS: The present results, together with those recently obtained in a MTLE population, suggest that preictal dynamical changes are a general phenomenon associated with seizure emergence in a wide population of patients with partial epilepsy whatever the localization of the epileptogenic focus. The possibility to anticipate the onset of seizures has considerable therapeutic consequences.