title: Application of magnetoencephalography in epilepsy patients with widespread spike or slow-wave activity.
abstract: OBJECTIVE
  To examine whether magnetoencephalography (MEG) can be used to determine patterns of brain activity underlying widespread paroxysms of epilepsy patients, thereby extending the applicability of MEG to a larger population of epilepsy patients.
  
  
  METHODS
  We studied two children with symptomatic localization-related epilepsy. Case 1 had widespread spikes in EEG with an operation scar from a resection of a brain tumor; Case 2 had hemispheric slow-wave activity in EEG with sensory auras. MEG was collected with a 204-channel helmet-shaped sensor array. Dynamic statistical parametric maps (dSPMs) were constructed to estimate the cortical distribution of interictal discharges for these patients. Equivalent current dipoles (ECDs) also were calculated for comparison with the results of dSPM.
  
  
  RESULTS
  In case 1 with widespread spikes, dSPM presented the major activity at the vicinity of the operation scar in the left frontal lobe at the peak of the spikes, and some activities were detected in the left temporal lobe just before the peak in some spikes. In case 2 with hemispheric slow waves, the most active area was located in the left parietal lobe, and additional activity was seen at the ipsilateral temporal and frontal lobes in dSPM. The source estimates correlated well with the ictal manifestation and interictal single-photon emission computed tomography (SPECT) findings for this patient. In comparison with the results of ECDs, ECDs could not express a prior activity at the left temporal lobe in case 1 and did not model well the MEG data in case 2.
  
  
  CONCLUSIONS
  We suggest that by means of dSPM, MEG is useful for presurgical evaluation of patients, not only with localized epileptiform activity, but also with widespread spikes or slow waves, because it requires no selections of channels and no time-point selection.
authors.affiliation: MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, USA. siraisi@nmr.mgh.harvard.edu
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shiraishi
authors.forename: Seppo P
authors.initials: SP
authors.lastname: Ahlfors
authors.forename: Steven M
authors.initials: SM
authors.lastname: Stufflebeam
authors.forename: Kyoko
authors.initials: K
authors.lastname: Takano
authors.forename: Maki
authors.initials: M
authors.lastname: Okajima
authors.forename: Susanne
authors.initials: S
authors.lastname: Knake
authors.forename: Keisaku
authors.initials: K
authors.lastname: Hatanaka
authors.forename: Shinobu
authors.initials: S
authors.lastname: Kohsaka
authors.forename: Shinji
authors.initials: S
authors.lastname: Saitoh
authors.forename: Anders M
authors.initials: AM
authors.lastname: Dale
authors.forename: Eric
authors.initials: E
authors.lastname: Halgren
mesh_terms: D000293:Adolescent; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000098:blood supply / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002675:Child, Preschool; D004569:Electroencephalography / Q000706:statistics & numerical data*; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D011300:Preoperative Care; D015899:Tomography, Emission-Computed, Single-Photon