Sequential analysis of fMRI images: A new approach to study human epileptic networks.
OBJECTIVE
The aim of this study was to introduce a new approach for analysis of functional magnetic resonance imaging (fMRI) data in order to illustrate the temporal development of the blood oxygenation level-dependent (BOLD) signal changes induced by epileptic seizures.


METHODS
In order to sequentially analyze the fMRI images acquired during epileptic seizures, a continuous series of echo planar imaging (EPI) scans covering the complete period of a seizure was acquired. Data were segmented into 10-s blocks. Each block, representing a unique experimental condition, was contrasted with a neutral (no seizure) baseline condition. Visual comparison of the activations from one block to the next highlighted the course of activations and deactivations during the seizure event. This analysis was applied to three independent seizures of one patient with peri-rolandic epilepsy secondary to chronic encephalitis: one seizure before epilepsy surgery and two after unsuccessful tailored resection. Observations were compared to results from invasive subdural electroencephalography (EEG) monitoring, single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM), and independent component analysis (ICA), a model-free method of BOLD-signal analysis.


RESULTS
The initial increase in BOLD signal occurred 10-40 s before clinical onset in the same location compared to the seizure-onset zone determined by invasive subdural evaluation and SISCOM. Sequential involvement of cortical and subcortical structures was in agreement with SISCOM, intracranial EEG recordings, and ICA results.


CONCLUSIONS
In selected patients, sequential analysis of changes in BOLD signal induced by epileptic seizures might represent a useful approach for investigating the temporal development of brain activity during epileptic seizures, thereby allowing imaging of those cerebral structures involved in seizure generation and propagation.
Donaire
Antonio
A
Hospital Clínic, Barcelona, Spain. donaire@clinic.ub.es
Falcón
Carlos
C
Carreno
Mar
M
Bargallo
Nuria
N
Rumià
Jordi
J
Setoain
Javier
J
Maestro
Iratxe
I
Boget
Teresa
T
Pintor
Luis
L
Agudo
Rolando
R
Falip
Merce
M
Fernández
Santiago
S
D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000503:physiopathology*; D017352:Echo-Planar Imaging / Q000706:statistics & numerical data; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology* / Q000601:surgery; D019305:Epilepsy, Rolandic / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D008297:Male; D010100:Oxygen / Q000097:blood; D013355:Subdural Space; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome
D010100:Oxygen