The ECD inclusion criteria were derived from the experience in our laboratory and used in an article by authors from our laboratory. 4 Twenty-four ECDs met our statistical evaluation criteria (goodness-of-fit >80% 100 nAm < dipole moment <400 nAm) and were used for further analysis. 2, 3 The first peak of activity was identified in each MEG IID, and the source was estimated with equivalent current dipoles (ECDs) by using a spheric head conductivity model. The data were high-pass filtered at 7 Hz and low-pass filtered at 40 Hz, the standard clinical values used at our institution for searching for spikes and the clinical definition of epileptic activity. Specifically, no definite spike propagation was suggested by the EEG recording.Ī neurophysiologist with special training in MEG epilepsy analysis analyzed the MEG waveforms and performed the source analysis. EEG showed synchronous bilateral frontal lobe monospikes or polyspikes. 1 For the EEG, a neurologist blinded to the MEG data and analysis detected spikes by using the transverse bipolar, banana bipolar, and monopolar montages. We visually identified the IIDs on MEG and EEG raw data and classified them according to a standard clinical classification. Coregistration between MEG/EEG and the MR imaging was performed by using anatomic fiduciary points and a high-resolution 3T MR imaging scanner (Siemens Medical Solutions, Erlangen, Germany) with a magnetization-prepared rapid acquisition of gradient echo sequence (TI/TR/TE, 2530/3.45/1100 ms 1.3-mm thickness). EEG consisted of 19 electrodes to approximate a 10- to 20-electrode system during the 48-minute measurement. She was referred for an MEG evaluation and a 3T MR imaging as part of a presurgical evaluation.Ī 306-channel whole-head MEG with simultaneous EEG (Vector View Elekta Neuromag, Helsinki, Finland) with a passband of 0.01–270 Hz and a sampling rate of 600 Hz was used for the measurements. The recent ictal EEG at 11 years of age revealed right and left frontal onset IDs with right frontal predominance. The first video EEG captured her ictal discharges (IDs) over the right frontal region with her habitual seizure at 6 years of age. The previous interictal EEG revealed right dominant bilateral frontal independent interictal discharges (IIDs) as well as occasional right occipital IIDs. Her neurologic findings and developmental milestones were normal except for a slightly delayed age of walking. The seizures consisted of an abrupt onset of intense fear, shouting, laughing, clapping, or limb thrashing lasting 15–40 seconds. The patient was an 11-year-old girl with refractory complex partial seizures since the age of 4.
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