title: Magnetoencephalographic mapping: basic of a new functional risk profile in the selection of patients with cortical brain lesions.
abstract: OBJECTIVE
  Surgical management of cortical lesions adjacent to or within the eloquent cerebral cortex requires a critical risk: benefit analysis of the procedure before intervention. This study introduced a measure of surgical risk, based on preoperative magnetoencephalographic (MEG) sensory and motor mapping, and tested its value in predicting surgical morbidity.
  
  
  METHODS
  Forty patients (21 men and 19 women; mean age, 36.5 yr) with cortical lesions (12 arteriovenous malformations and 28 tumors) in the vicinity of the sensorimotor cortex were classified into high-, medium-, or low-risk categories by using the MEG-defined functional risk profile (FRP). This was based on the minimal distance between the lesion margin and the sensory and motor MEG sources, superimposed on a magnetic resonance imaging scan. Case management decisions were based on the MEG mapping-derived FRP in combination with biopsy pathological findings, radiographic findings, and anatomic characteristics of the lesion. A recently developed protocol was used to transform MEG source locations into the stereotactic coordinate system. This procedure provided intraoperative access to MEG data in combination with stereotactic anatomic data displays routinely available on-line during surgery.
  
  
  RESULTS
  It was determined that 11 patients diagnosed as having gliomas had high FRPs. The margin of the lesion was less than 4 mm from the nearest MEG dipole or involved the central sulcus directly. A nonoperative approach was used for six patients of this group, based on the MEG mapping-derived FRP. In the group with arteriovenous malformations, 6 of 12 patients with high or medium FRPs underwent nonoperative therapy. The remaining 28 patients, whose lesions showed satisfactory FRPs, underwent uneventful lesion resection, without postoperative neurological deficits.
  
  
  CONCLUSIONS
  Our results suggest that MEG mapping-derived FRPs can serve as powerful tools for use in presurgical planning and during surgery.
authors.affiliation: Department of Physiology, New York University School of Medicine, New York, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hund
authors.forename: A R
authors.initials: AR
authors.lastname: Rezai
authors.forename: E
authors.initials: E
authors.lastname: Kronberg
authors.forename: J
authors.initials: J
authors.lastname: Cappell
authors.forename: M
authors.initials: M
authors.lastname: Zonenshayn
authors.forename: U
authors.initials: U
authors.lastname: Ribary
authors.forename: P J
authors.initials: PJ
authors.lastname: Kelly
authors.forename: R
authors.initials: R
authors.lastname: Llinás
mesh_terms: D000328:Adult; D000368:Aged; D001925:Brain Damage, Chronic / Q000175:diagnosis* / Q000503:physiopathology; D001931:Brain Mapping / Q000295:instrumentation*; D001932:Brain Neoplasms / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D002540:Cerebral Cortex / Q000098:blood supply / Q000503:physiopathology / Q000601:surgery*; D004867:Equipment Design; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D015225:Magnetoencephalography / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology / Q000601:surgery; D009460:Neurologic Examination; D011183:Postoperative Complications / Q000175:diagnosis* / Q000503:physiopathology; D012306:Risk; D012307:Risk Factors; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D013003:Somatosensory Cortex / Q000503:physiopathology / Q000601:surgery; D013238:Stereotaxic Techniques / Q000295:instrumentation