Abstracts

Rationale: In patients with mesial lobe epilepsy, it is often challenging to identify the epileptogenic zone where is considered to be resected, because of the absence of definite lateralizing and localizing information in various neuro-imaging and the lack of definite informative encephalography (EEG) correlates. The aim of this study was to investigate that the spatial filtering analysis: dynamic statistical parametric mapping (dSPM) of ictal magnetoencephalographic (MEG) activities could provide valuable information on the lateralization of the epileptogenic zone.Methods: The objectives were two patients whose ictal MEG were recorded. MEG was performed in a magnetically shielded room using a 204-channel planner type gradiometer and 102ch magnetometer (Vector View System, Elekta AB, Stockholm, Sweden) with a 600 Hz sampling rate. EEG was simultaneously recorded using 20 scalp electrodes, placed according to the international 10–20 system. Significant magnetic field change at ictal origin were superimposed on magnetic resonance images (MRI) using dSPM analysis and MEG interictal spike sources were also demonstrated on individual MRI using a single dipole method to project equivalent current dipoles (ECDs). We investigated epileptogenic zone by MEG data described above, EEG, 99mTc-ECD-SPECT and 18F-FDG-PET.Results: Patient 1; 13 years old boy. He had seizures (automatic behavior with impairment of consciousness) a few times a day from 12 years old. There were no remarkable abnormal lesions in brain MRI, though bilateral frontal lobe hypoperfusion on 99mTc-ECD-SPECT and hypometabolism on 18F-FDG-PET during interictal period. Inter-ictal EEG showed spikes in midline frontal. ECDs were clustered at the mesial frontal lobe with slightly right side dominancy. Ictal EEG showed no laterality but, dSPM showed significant magnetic field changes at nucleus accumbens in the right frontal lobe, then propagated to the right temporal lobe. Patient 2; 8 years old girl. She had left side gyratory seizures with levoversion at 6 years old. At present she had tonic movement seizures subsequent to scintillation feeling at the left side eye sight more than 10 times a day. Brain MRI, 99mTc-ECD-SPECT and 18F-FDG-PET had no abnormalities. Interictal EEG showed the right frontal dominant spikes. Ictal EEG showed epileptic spikes originated from the bilateral centro-temporal. Interictal MEG showed cluster of ECDs at the right parietal lobe, and dSPM showed significant magnetic field changes at the same lesions.Conclusions: dSPM analysis of ictal MEG is useful for laterality diagnosis among the patients with mesial lobe epilepsy and can demonstrate the propagation of seizures activities adequately.