John Libbey Eurotext

Identifying seizure-onset zone and visualizing seizure spread by fMRI: a case report Volume 10, numéro 2, June 2008

Department of Neurosurgery, University of Pécs, Faculty of Business and Economics of University of Pécs, Department of Neurology, University of Pécs, Epilepsy Center, Szt. István Hospital, Budapest, Pécs Diagnostic Institute of University of Pécs, Hungary

Aim. To visualize by ictal, functional MRI, the initial haemodynamic change (i.e. putative seizure-onset zone) and subsequent seizure spread during an epileptic seizure. Methods. A 20-year-old woman was investigated during a simple partial seizure consisting of right-sided mouth clonus. An internal reference curve, correlated with signal change pixelwise, was applied to obtain correlation coefficient maps. The reference curve was shifted scan by scan to examine the correlation at each time point. To demonstrate seizure onset and propagation, a lag time map was produced showing the temporal sequence of activation in various brain regions. Results. fMRI analysis showed that the lower part of the insular cortex was activated first, and its signal alteration preceded the clinical beginning of the seizure (i.e. mouth clonus) by more than one minute. Most of the activations started before clinical seizure onset. The activation corresponding to the motor area of the right face showed only a 7.5 second-long, pre-ictal phase. BOLD signal alterations were also observed in the left caudate nucleus, left thalamus, along with various areas of the left cerebral and cerebellum hemispheres. Conclusions. The present study demonstrates a whole-brain activity simultaneously in time and space, during an epileptic seizure. Our results also support the existence of the pre-ictal state in epilepsy. Replication of our results would be of major interest for presurgical evaluation of patients with drug-resistant epilepsy.