GENERALIZED EPILEPTIC DISCHARGES AND THE DEFAULT STATE OF THE BRAIN
Abstract number :
1.115
Submission category :
Year :
2005
Submission ID :
5167
Source :
www.aesnet.org
Presentation date :
12/3/2005 12:00:00 AM
Published date :
Dec 2, 2005, 06:00 AM
Authors :
Jean Gotman, Christophe Grova, Andrew P. Bagshaw, Eliane Kobayashi, Yahya Aghakhani, and Fran[ccedil]ois Dubeau
The objective of this study was to evaluate the brain regions showing increased and decreased metabolism in patients at the time of generalized bursts of epileptic discharges, in order to understand their mechanism of generation and their effect on brain function. Changes in BOLD signal were obtained in response to epileptic discharges observed in the EEG of 15 patients with idiopathic generalized epilepsy, by recording the EEG during the fMRI study. A group analysis was performed to determine the regions of positive BOLD response (activation) and negative BOLD response (deactivation) that were common to the patients. Significant group activations were found bilaterally and symmetrically in the thalamus, mesial mid-frontal region, insulae, midline and bilateral cerebellum and on the borders of the lateral ventricles. Significant group deactivations were found bilaterally and symmetrically in the anterior frontal and parietal region and in the posterior cingulate gyri, and in the left posterior temporal region. Activations in the thalamus and mid-frontal region confirm known involvement of these regions in the generation or spread of generalized epileptic discharges. Involvement of the insulae in generalized discharges has not been described before. Cerebellar activation is not believed to reflect the generation of discharges. Deactivations in frontal and parietal regions followed remarkably the pattern of the default state of brain function that has been described extensively in the literature on brain activation (Raichle et al, 2001), and which corresponds to a state of passive attention. This suspension or attenuation of the default state may reflect the actual state of reduced responsiveness observed in patients as a result of spike-wave discharges. This state would thus not be the direct result of the epileptic discharge.
Raichle ME, MacLeod AM, Snyder AZ, Powers WJ, Gusnard DA, Shulman GL. A default mode of brain function. Proc Natl Acad Sci U S A 2001; 98(2): 676-82. (Supported by Canadian Institutes of Health Research.)