SIMULTANEOUS EEG AND FMRI STUDY OF THE OCCIPITAL LOBE SEIZURES
Abstract number :
1.026
Submission category :
Year :
2002
Submission ID :
1598
Source :
www.aesnet.org
Presentation date :
12/7/2002 12:00:00 AM
Published date :
Dec 1, 2002, 06:00 AM
Authors :
Seyed M. Mirsattari, John R. Ives, Ravi S. Menon, Laio-Wu S. Leung, Warren T. Blume, Nagalingan Rajakumar, Frank Bihari. Clinical Neurological Sciences, University of Western Ontario, London, Ontario, Canada; Neurology, Harvard University, Boston, MA; Fun
RATIONALE: Functional MRI (fMRI) has the potential to overcome limitations inherent to EEG study of epileptiform activity and provide real time cortical and subcortical activation maps of epileptiform discharges. The feasibility of simultaneous fMRI/EEG was investigated in an animal model of epilepsy.
METHODS: Male Spargue-Dawley rats were anesthetized with isoflurane. Burr holes were made using Paxinos and Watson[ssquote]s stereotactic atlas as the reference. Using a MRI compatible stereotactic frame of our own design, carbon fiber EEG electrodes were placed above the dura. EEG was transmitted from the magnet to the recording system using a modified version of a device developed by Ives et al. A microsyringe was adavanced into the primary visual cortex (V1) of the animal. Various degrees of epileptiform activity were induced in the magnet using by altering the dose of intracortically injected sodium penicillin G (0-100 IU) in an injection volume of 0.2 [mu]l. Segmented and navigator-echo corrected EPI sequences developed for fMRI on our 4 T Varian whole body MR scanner were used along with a custom designed RF coil. A 5 x 5 cm FOV with eleven 2 mm slices was used, resulting in an in-plane resolution of 391 microns. The 11 slices could be repeated with a TR of 1.7 s at a TE of 15 ms. The animals were then sacrificed and perfused with 4% PFA for immunohistochemistry using C-fos and parvalbumin double labeling.
RESULTS: Activation maps with fMRI were made using a pixel cross-correlation method using the low-pass filtered EEG as a reference vector. Activated areas in fMRI bore a remarkable resemblance to the autoradiography studies of Collins and Caston (1979) showing the utility of a multimodality approach to study of epileptic activities in discerning spread of occipital seizures in a pattern predicted by functional connectivity of the cortical and subcortical visual systems.
CONCLUSIONS: Multimodality study of seizures and other epileptiform activities is a promising stool to study the neurobiology of epileptiform discharges, their precise anatomic localization and propagation.
[Supported by: Canadian Institute of Health Research]