EEG/fMRI study of ictal and interictal epileptic activity: methodological issues and future perspectives in clinical practice.
OBJECTIVE
Electroencephalography/functional magnetic resonance imaging (EEG/fMRI) has been proposed recently as a tool to study electrophysiological activity and, consequently, detect brain regions activated during epileptiform EEG abnormalities. The purpose of the study was to review our two-year experience with studying ictal and interictal activities in patients with epilepsy.


METHODS
Using EEG/fMRI, we studied hemodynamic changes associated with ictal and interictal EEG abnormalities in 43 patients with partial (31 cases) or generalized (12 cases) epilepsy. Using two different paradigms (block design and event-related design), we studied several forms of EEG activity consisting of (i) interictal abnormalities constantly elicitable by specific stimulation (8 cases); (ii) focal and generalized interictal activity, such as focal spikes or typical and atypical generalized spike-and-wave discharges (18 cases); and (iii) focal and generalized ictal electro-clinical activity, such as tonic seizures or pseudo-absences in frontal lobe epilepsy, typical absences in idiopathic generalized epilepsy, complex partial seizures in temporal lobe epilepsy, and perisylvian seizures in special syndromes (17 patients).


RESULTS
EEG/fMRI revealed clear hemodynamic changes related to EEG abnormalities in 21 patients. In 18 of these patients, the changes were highly concordant with electro-clinical findings. In the remaining 22 patients, fMRI analysis data failed to show activation or deactivation clusters, probably owing either to lack or inadequate amount of temporal distribution of abnormal EEG activity, or to intrinsic methodological problems.


CONCLUSIONS
By defining the electro-clinical and hemodynamic correlates of EEG activity, fMRI may shed light on the neurophysiological mechanisms underlying epileptic phenomena. However, as several methodological issues have yet to be addressed, further studies are warranted to assess the reliability and usefulness of EEG/fMRI in clinical practice.
Di Bonaventura
Carlo
C
Department of Neurological Sciences, University of Rome, La Sapienza, Rome, Italy. c_dibonaventura@yahoo.it
Vaudano
Anna E
AE
Carnì
Marco
M
Pantano
Patrizia
P
Nucciarelli
Valter
V
Garreffa
Girolamo
G
Maraviglia
Bruno
B
Prencipe
Massimiliano
M
Bozzao
Luigi
L
Manfredi
Mario
M
Giallonardo
Anna T
AT
D000293:Adolescent; D000328:Adult; D001775:Blood Circulation / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography / Q000379:methods* / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000706:statistics & numerical data; D010100:Oxygen / Q000097:blood; D014743:Videotape Recording
D010100:Oxygen