title: Can ictal-MEG obviate the need for phase II monitoring in people with drug-refractory epilepsy? A prospective observational study.
abstract: OBJECTIVE
  To determine if ictal-magnetoencephalography (ictal-MEG) source localization (SL) added information towards delineating the ictal-onset zone (IOZ), whether and how it helped final decision-making in epilepsy-surgery.
  
  
  METHODS
  Definite focal clusters on ictal-MEG were available for 32 DRE-patients, data was analyzed (single equivalent current dipole (ECD) model), SL done. Clinical history, long-term video-EEG (VEEG) monitoring, epilepsy-protocol MRI, FDG-PET, ictal-SPECT and interictal-MEG were discussed at the multispeciality Epilepsy Surgery Case-conference (ESC). Cases were reviewed with ictal-MEG SL presented only at the last ESC (after decision using other available modalities). Patients were grouped as VEEG localization and MRI-lesion concordant (Group-A), discordant (Group-B), and no MRI-lesion (Group-C). Final hypothesis or decision, surgical outcome in those operated, and how ictal-MEG data influenced them were recorded.
  
  
  RESULTS
  Five lesion-negative patients had identification of lesions after review of MRI with ictal-MEG SL. The difference between numbers of patients cleared for surgery without and with ictal MEG data was statistically significant (p=0.0044); but the difference in those cleared for phase II monitoring was not (p=1.00). Ictal MEG influenced decisions on possibility of surgery in 9 and converted decisions of phase II monitoring in 11 patients to electrocorticography-guided lesionectomy (20 in all; Group A-11, Group B-4, Group C-5); five were operated, with good seizure-control on follow-up.
  
  
  CONCLUSIONS
  Delineation of IOZ by ictal-MEG helped convert DRE patients unsuitable for surgery or planned for phase II monitoring into candidates suitable for surgery, even ECoG-guided resections, and resulted in favorable outcomes in those who were operated.
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: bhargavi.ramanujam@gmail.com.
authors.forename: Bhargavi
authors.initials: B
authors.lastname: Ramanujam
authors.affiliation: National Brain Research Centre, Manesar, Haryana, India. Electronic address: kbharti82@gmail.com.
authors.forename: Kamal
authors.initials: K
authors.lastname: Bharti
authors.affiliation: National Brain Research Centre, Manesar, Haryana, India. Electronic address: vibs999@gmail.com.
authors.forename: Vibhin
authors.initials: V
authors.lastname: Viswanathan
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: drajaygarg@gmail.com.
authors.forename: Ajay
authors.initials: A
authors.lastname: Garg
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: madhavi.dave.97@gmail.com.
authors.forename: Madhavi
authors.initials: M
authors.lastname: Tripathi
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: drcsbal@gmail.com.
authors.forename: Chandrashekhar
authors.initials: C
authors.lastname: Bal
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: saratpchandra2@gmail.com.
authors.forename: P Sarat
authors.initials: PS
authors.lastname: Chandra
authors.affiliation: All India Institute of Medical Sciences, New Delhi, India. Electronic address: manjari.tripathi1@gmail.com.
authors.forename: Manjari
authors.initials: M
authors.lastname: Tripathi
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D001931:Brain Mapping; D002648:Child; D000069279:Drug Resistant Epilepsy / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult
keywords: Drug refractory epilepsy; Epilepsy surgery; Ictal MEG; Intracranial EEG; Source localization