Generalized Spike and Waves: Effect of Discharge Duration on Brain Networks as Revealed by BOLD fMRI
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In the past decade, the possibility of combining recordings of EEG and functional MRI (EEG–fMRI), has brought a new insight into the brain network underlying generalized spike wave discharges (GSWD). Nevertheless, how GSWD duration influences this network is not fully understood. In this study we aim to investigate whether GSWD duration had a threshold (non-linear) and/or a linear effect on the amplitude of the associated BOLD changes in any brain regions. This could help in elucidating if there is an hemodynamic background supporting the differentiation between interictal and ictal events. We studied a population of 42 patients with idiopathic generalized epilepsies (IGE) who underwent resting-state EEG–fMRI recordings in three centres (London, UK; Modena, Italy; Rome, Italy), applying a parametric analysis of the GSWD duration. Patients were classified as having Childhood Absence epilepsy, Juvenile Absence Epilepsy, or Juvenile Myoclonic Epilepsy. At the population level linear GSWD duration-related BOLD signal changes were found in a network of brain regions: mainly BOLD increase in thalami and cerebral ventricles, and BOLD decrease in posterior cingulate, precuneus and bilateral parietal regions. No region of significant BOLD change was found in the group analysis for the non-linear effect of GSWD duration. To explore the possible effect of both the different IGE sub-syndromes and the different protocols and scanning equipment used in the study, a full-factorial ANOVA design was performed revealing no significant differences. These findings support the idea that the amplitude of the BOLD changes is linearly related to the GSWD duration with no universal threshold effect of spike and wave duration on the brain network supporting this activity.
KeywordsEEG–fMRI Idiopathic generalized epilepsy Generalized spike and wave Absence seizure BOLD effect
This study was undertaken at UCLH/UCL who received a proportion of funding from the Department of Health’s NIHR Biomedical Research Centres funding scheme. EEG–fMRI co-registrations in Modena-Italy were supported by a Grant of ‘‘Fondazione Cassa di Risparmio di Modena,’’ Modena, Italy: Ricerca Internazionale 2010. Moreover, the work was funded through a Grant from the Medical Research Council (MRC Grant Number G0301067), European Federation of Neurological Society (EFNS) fellowship (edition 2007/2008), Funding received from the Central and East London NIHR CLRN, Funding received by a Grant “Mechanism, diagnosis and treatment of drug-resistant epilepsy; Area 1a Innovative Research” from Emilia-Romagna Region, Italy. M.P. was supported by a PhD bursary from University of Modena and Reggio Emilia. A.E.V. was supported by a research bursary from the Grant “Ricerca Internazionale 2010” of “Fondazione Cassa di Risparmio di Modena”. U.C. was funded by the Higher Education Commission of Pakistan. We are grateful to the Epilepsy Society, Chalfont St Peter, Buckinghamshire-UK, for supporting the MRI scanner and research facilities.
Conflict of Interest
We have no conflicts of interest to declare.
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