Concordance of Epileptic Networks Associated with Epileptic Spikes Measured by High-Density EEG and Fast fMRI.
OBJECTIVE
The present study aims to investigate whether a newly developed fast fMRI called MREG (magnetic resonance encephalography) measures metabolic changes related to interictal epileptic discharges (IED). For this purpose BOLD changes are correlated with the IED distribution and variability.


METHODS
Patients with focal epilepsy underwent EEG-MREG using a 64 channel cap. IED voltage maps were generated using 32 and 64 channels and compared regarding their correspondence to the BOLD response. The extents of IEDs (defined as number of channels with >50% of maximum IED negativity) were correlated with the extents of positive and negative BOLD responses. Differences in inter-spike variability were investigated between interictal epileptic discharges (IED) sets with and without concordant positive or negative BOLD responses.


RESULTS
17 patients showed 32 separate IED types. In 50% of IED types the BOLD changes could be confirmed by another independent imaging method. The IED extent significantly correlated with the positive BOLD extent (p = 0.04). In 6 patients the 64-channel EEG voltage maps better reflected the positive or negative BOLD response than the 32-channel EEG; in all others no difference was seen. Inter-spike variability was significantly lower in IED sets with than without concordant positive or negative BOLD responses (with p = 0.04).


CONCLUSIONS
Higher density EEG and fast fMRI seem to improve the value of EEG-fMRI in epilepsy. The correlation of positive BOLD and IED extent could suggest that widespread BOLD responses reflect the IED network. Inter-spike variability influences the likelihood to find IED concordant positive or negative BOLD responses, which is why single IED analysis may be promising.
Department of Neuropediatrics and Muscular Diseases, University Medical Center Freiburg, Freiburg, Germany.
Vera
V
Jäger
Section for Epileptology, University Medical Center Freiburg, Freiburg, Germany.
Matthias
M
Dümpelmann
Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
Pierre
P
LeVan
Section for Epileptology, University Medical Center Freiburg, Freiburg, Germany.
Georgia
G
Ramantani
Department for Neuroradiology, University Medical Center Freiburg, Freiburg, Germany.
Irina
I
Mader
Section for Epileptology, University Medical Center Freiburg, Freiburg, Germany.
Andreas
A
Schulze-Bonhage
Department of Neuropediatrics and Muscular Diseases, University Medical Center Freiburg, Freiburg, Germany.
Julia
J
Jacobs
D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology; D002648:Child; D004569:Electroencephalography / Q000379:methods*; D004827:Epilepsy / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult