EEG correlated functional MRI and postoperative outcome in focal epilepsy.
BACKGROUND
The main challenge in assessing patients with epilepsy for resective surgery is localising seizure onset. Frequently, identification of the irritative and seizure onset zones requires invasive EEG. EEG correlated functional MRI (EEG-fMRI) is a novel imaging technique which may provide localising information with regard to these regions. In patients with focal epilepsy, interictal epileptiform discharge (IED) correlated blood oxygen dependent level (BOLD) signal changes were observed in approximately 50% of patients in whom IEDs are recorded. In 70%, these are concordant with expected seizure onset defined by non-invasive electroclinical information. Assessment of clinical validity requires post-surgical outcome studies which have, to date, been limited to case reports of correlation with intracranial EEG. The value of EEG-fMRI was assessed in patients with focal epilepsy who subsequently underwent epilepsy surgery, and IED correlated fMRI signal changes were related to the resection area and clinical outcome.


METHODS
Simultaneous EEG-fMRI was recorded in 76 patients undergoing presurgical evaluation and the locations of IED correlated preoperative BOLD signal change were compared with the resected area and postoperative outcome.


RESULTS
21 patients had activations with epileptic activity on EEG-fMRI and 10 underwent surgical resection. Seven of 10 patients were seizure free following surgery and the area of maximal BOLD signal change was concordant with resection in six of seven patients. In the remaining three patients, with reduced seizure frequency post-surgically, areas of significant IED correlated BOLD signal change lay outside the resection. 42 of 55 patients who had no IED related activation underwent resection.


CONCLUSIONS
These results show the potential value of EEG-fMRI in presurgical evaluation.
Thornton
Rachel
R
Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, UK. r.thornton@ion.ucl.ac.uk
Laufs
Helmut
H
Rodionov
Roman
R
Cannadathu
Sajitha
S
Carmichael
David W
DW
Vulliemoz
Serge
S
Salek-Haddadi
Afraim
A
McEvoy
Andrew W
AW
Smith
Shelagh M
SM
Lhatoo
Samden
S
Elwes
Robert D C
RD
Guye
Maxime
M
Walker
Matthew C
MC
Lemieux
Louis
L
Duncan
John S
JS
D001921:Brain / Q000473:pathology / Q000503:physiopathology; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D019635:Neurosurgical Procedures; D010100:Oxygen / Q000097:blood; D011184:Postoperative Period; D012640:Seizures / Q000473:pathology / Q000503:physiopathology; D016896:Treatment Outcome
D010100:Oxygen