MEG time-frequency analyses for pre- and post-surgical evaluation of patients with epileptic rhythmic fast activity.
OBJECTIVE
To evaluate the effectiveness of surgery for epilepsy, we analyzed rhythmic fast activity by magnetoencephalography (MEG) before and after surgery using time-frequency analysis. To assess reliability, the results obtained by pre-surgical MEG and intraoperative electrocorticography were compared.


METHODS
Four children with symptomatic localization-related epilepsy caused by circumscribed cortical lesion were examined in the present study using 204-channel helmet-shaped MEG with a sampling rate of 600Hz. One patient had dysembryoplastic neuroepithelial tumor (DNT) and three patients had focal cortical dysplasia (FCD). Aberrant areas were superimposed, to reconstruct 3D MRI images, and illustrated as moving images.


RESULTS
In three patients, short-time Fourier transform (STFT) analyses of MEG showed rhythmic activities just above the lesion with FCD and in the vicinity of DNT. In one patient with FCD in the medial temporal lobe, rhythmic activity appeared in the ipsilateral frontal lobe and temporal lateral aspect. These findings correlate well with the results obtained by intraoperative electrocorticography. After the surgery, three patients were relieved of their seizures, and the area of rhythmic MEG activity disappeared or become smaller. One patient had residual rhythmic MEG activity, and she suffered from seizure relapse.


CONCLUSIONS
Time-frequency analyses using STFT successfully depicted MEG rhythmic fast activity, and would provide valuable information for pre- and post-surgical evaluations to define surgical strategies for patients with epilepsy.
Sueda
Keitaro
K
Department of Pediatrics, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan.
Takeuchi
Fumiya
F
Shiraishi
Hideaki
H
Nakane
Shingo
S
Asahina
Naoko
N
Kohsaka
Shinobu
S
Nakama
Hideyuki
H
Otsuki
Taisuke
T
Sawamura
Yutaka
Y
Saitoh
Shinji
S
D001931:Brain Mapping; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D002648:Child; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008297:Male; D011877:Radionuclide Imaging; D016896:Treatment Outcome