Using patient-specific hemodynamic response functions in combined EEG-fMRI studies in epilepsy.
Combining electroencephalogram (EEG) and functional MRI (fMRI) allows localization of brain regions activated as a result of epileptic spikes. The statistical analysis of fMRI data usually includes a standard model of the hemodynamic response function (HRF) but it is not known how well this fits the actual HRF of epileptic spikes. The objective of this exploratory study was to compare the activated areas and t-statistical scores obtained with a standard HRF to those obtained with a patient-specific HRF. Eight patients with focal epilepsy were studied. We obtained an estimate of the patient-specific HRFs for each patient at the local maximum of activation in the standard HRF analysis. The activated areas obtained with the patient-specific HRFs were larger or similar to the originally activated areas. Additional activated areas were seen in five patients, and most were compatible with the EEG and anatomical MRI localization of epileptogenic and lesional regions. Using patient-specific HRFs brings increased sensitivity to the analysis of epileptic spikes by EEG-fMRI.
Kang
Joong Koo
JK
Montreal Neurological Institute, 3801 University Street, McGill University,Montréal, Québec, Canada H3A 2B4.
Bénar
Christian- G
C
Al-Asmi
Abdullah
A
Khani
Yahya Agha
YA
Pike
G Bruce
GB
Dubeau
François
F
Gotman
Jean
J
D002560:Cerebrovascular Circulation / Q000502:physiology*; D004569:Electroencephalography; D004827:Epilepsy / Q000473:pathology* / Q000503:physiopathology*; D007839:Functional Laterality / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D012015:Reference Standards