title: Intraoperative Subcortical Fiber Mapping with Subcortico-Cortical Evoked Potentials.
abstract: OBJECTIVE
  During brain surgery, there are difficulties associated with identifying subcortical fibers with no clear landmarks. We evaluated the usefulness of cortical evoked potentials with subcortical stimuli (subcortico-cortical evoked potential [SCEP]) in identifying subcortical fibers intraoperatively.
  
  
  METHODS
  We used SCEP to identify the pyramidal tract in 4 patients, arcuate fasciculus in 1 patient, and both in 2 patients during surgical procedures. After resection, a 1 × 4-electrode plate was placed on the floor of the removal cavity and 1-Hz alternating electrical stimuli were delivered to this electrode. A 4 × 5 recording electrode plate was placed on the central cortical areas to map the pyramidal tract and temporoparietal cortical areas for the arcuate fasciculus. SCEPs were obtained by averaging electrocorticograms time locked to the stimulus onset.
  
  
  RESULTS
  The subcortical stimulation within 15 mm of the target fiber induced cortical evoked potentials in the corresponding areas, whereas the stimulation apart from 20 mm did not. Five patients showed transient worsening of neurologic symptoms after surgery. However, all patients recovered.
  
  
  CONCLUSIONS
  SCEP was useful for identifying subcortical fibers and confirmed the preservation of these fibers. This technique is expected to contribute to the effectiveness and safety of resective surgery in patients with lesions close to eloquent areas.
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan. Electronic address: enatsur@sapmed.ac.jp.
authors.forename: Rei
authors.initials: R
authors.lastname: Enatsu
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Kanno
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Shunya
authors.initials: S
authors.lastname: Ohtaki
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Akiyama
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Ochi
authors.affiliation: Department of Neurosurgery, Sapporo Medical University, Sapporo, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mikuni
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D004558:Electric Stimulation; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011712:Pyramidal Tracts / Q000502:physiology*
keywords: Arcuate fasciculus; Pyramidal tract; Subcortical stimulation; Subcortico-cortical evoked potential