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Epilepsy Research 53 (2003) 173185 Epileptic seizures are preceded by a decrease

Summary: Epilepsy Research 53 (2003) 173­185
Epileptic seizures are preceded by a decrease
in synchronization
Florian Mormanna,b,, Thomas Kreuza,c, Ralph G. Andrzejaka,c,
Peter Davidb, Klaus Lehnertza, Christian E. Elgera
a Department of Epileptology, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany
b Helmholtz Institute for Radiation and Nuclear Physics, University of Bonn, Nußallee 14-16, 53115 Bonn, Germany
c John von Neumann Insitute for Computing, Forschungszentrum Jülich, 52425 Jülich, Germany
Received 18 October 2002; accepted 30 December 2002
The exact mechanisms leading to the occurrence of epileptic seizures in humans are still poorly understood. It is widely accep-
ted, however, that the process of seizure generation is closely associated with an abnormal synchronization of neurons. In order
to investigate this process, we here measure phase synchronization between different regions of the brain using intracranial EEG
recordings. Based on our preliminary finding of a preictal drop in synchronization, we investigate whether this phenomenon can
be used as a sensitive and specific criterion to characterize a preseizure state and to distinguish this state from the interictal interval.
Applying an automated technique for detecting decreased synchronization to EEG recordings from a group of 18 patients
with focal epilepsy comprising a total of 117 h, we observe a characteristic decrease in synchronization prior to 26 out of 32
analyzed seizures at a very high specificity as tested on interictal recordings. The duration of this preictal state is found to range
from several minutes up to a few hours. Investigation of the spatial distribution of preictal desynchronization indicates that the
process of seizure generation in focal epilepsy is not necessarily confined to the focus itself but may instead involve more distant,


Source: Andrzejak, Ralph Gregor - Departament de Tecnologia, Universitat Pompeu Fabra


Collections: Computer Technologies and Information Sciences