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Brain Advance Access published online on June 23, 2005
Brain, doi:10.1093/brain/awh533
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© The Author (2005). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oupjournals.org
Received October 5, 2004
Revised March 19, 2005
Accepted April 4, 2005

Article

Functional MRI of the pre-ictal state

Paolo Federico 1, David F. Abbott 2, Regula S. Briellmann 2, A. Simon Harvey 3, and Graeme D. Jackson 4*

1 Brain Research Institute, Heidelberg West, Victoria, Australia; Department of Medicine, The University of Melbourne, Australia; Department of Clinical Neurosciences, University of Calgary, Alberta, Canada
2 Brain Research Institute, Heidelberg West, Victoria, Australia; Department of Medicine, The University of Melbourne, Australia
3 Brain Research Institute, Heidelberg West, Victoria, Australia; Department of Medicine, The University of Melbourne, Australia; Department of Neurology, Royal Children's Hospital, Parkville, Victoria, Australia
4 Brain Research Institute, Heidelberg West, Victoria, Australia; Department of Medicine, The University of Melbourne, Australia; Department of Radiology, The University of Melbourne, Australia; Department of Neurology, Royal Children's Hospital, Parkville, Victoria, Australia

* To whom correspondence should be addressed.
Graeme D. Jackson, E-mail: BRI{at}brain.org.au


  Abstract

The mechanisms underlying the transition from interictal to ictal states are poorly understood. Non-linear mathematical analysis of EEG frequency components has confirmed the presence of a pre-ictal state in focal epilepsy. We report on functional MRI (fMRI) analysis of the pre-ictal state in three patients with intractable focal epilepsy. Each subject had a typical partial seizure in the scanner while continuous blood oxygen level dependent (BOLD) fMRI images were acquired. The pre-ictal BOLD changes were first analysed by statistically comparing BOLD signals of two one-minute blocks. Further examination of the full time course was then performed. Each patient showed highly significant, focal BOLD signal changes. In Patient 1, a striking pre-ictal BOLD signal increase was seen over the region of the seizure focus identified on complementary epilepsy investigations. No significant BOLD signal decreases were observed. Patient 2 showed widespread pre-ictal BOLD increase contralateral to the presumed seizure focus, as well as a focal BOLD decrease near the presumed seizure focus. In Patient 3, pre-ictal BOLD increase was co-localized with the site of hyperperfusion seen on ictal single photon emission computed tomography (SPECT). However, this was contralateral to the seizure focus localization based on seizure symptomatology. No significant BOLD decreases were seen. The time course data in each patient studied showed change of the BOLD signal several minutes before the onset of the seizure. Highly significant BOLD fMRI signal changes occur before the onset of seizures, supporting the presence of a pre-ictal state. These changes can be localized to the site of the presumed seizure focus, as well as to other brain regions, suggesting that the pre-ictal BOLD signal changes and their underlying mechanisms are complex.

Keywords: pre-ictal; functional MRI; epilepsy; seizure; EEG; magnetic resonance.
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