title: Intraoperative cortico-cortical evoked potentials for the evaluation of language function during brain tumor resection: initial experience with 13 cases.
abstract: OBJECTIVE
  The objective in the present study was to evaluate the usefulness of cortico-cortical evoked potentials (CCEP) monitoring for the intraoperative assessment of speech function during resection of brain tumors.
  
  
  METHODS
  Intraoperative monitoring of CCEP was applied in 13 patients (mean age 34 ± 14 years) during the removal of neoplasms located within or close to language-related structures in the dominant cerebral hemisphere. For this purpose strip electrodes were positioned above the frontal language area (FLA) and temporal language area (TLA), which were identified with direct cortical stimulation and/or preliminary mapping with the use of implanted chronic subdural grid electrodes. The CCEP response was defined as the highest observed negative peak in either direction of stimulation. In 12 cases the tumor was resected during awake craniotomy.
  
  
  RESULTS
  An intraoperative CCEP response was not obtained in one case because of technical problems. In the other patients it was identified from the FLA during stimulation of the TLA (7 cases) and from the TLA during stimulation of the FLA (5 cases), with a mean peak latency of 83 ± 15 msec. During tumor resection the CCEP response was unchanged in 5 cases, decreased in 4, and disappeared in 3. Postoperatively, all 7 patients with a decreased or absent CCEP response after lesion removal experienced deterioration in speech function. In contrast, in 5 cases with an unchanged intraoperative CCEP response, speaking abilities after surgery were preserved at the preoperative level, except in one patient who experienced not dysphasia, but dysarthria due to pyramidal tract injury. This difference was statistically significant (p < 0.01). The time required to recover speech function was also significantly associated with the type of intraoperative change in CCEP recordings (p < 0.01) and was, on average, 1.8 ± 1.0, 5.5 ± 1.0, and 11.0 ± 3.6 months, respectively, if the response was unchanged, was decreased, or had disappeared.
  
  
  CONCLUSIONS
  Monitoring CCEP is feasible during the resection of brain tumors affecting language-related cerebral structures. In the intraoperative evaluation of speech function, it can be a helpful adjunct or can be used in its direct assessment with cortical and subcortical mapping during awake craniotomy. It can also be used to predict the prognosis of language disorders after surgery and decide on the optimal resection of a neoplasm.
authors.affiliation: Department of Neurosurgery;
authors.forename: Taiichi
authors.initials: T
authors.lastname: Saito
authors.forename: Manabu
authors.initials: M
authors.lastname: Tamura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Muragaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Maruyama
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kubota
authors.forename: Satoko
authors.initials: S
authors.lastname: Fukuchi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nitta
authors.forename: Mikhail
authors.initials: M
authors.lastname: Chernov
authors.forename: Saori
authors.initials: S
authors.lastname: Okamoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sugiyama
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kurisu
authors.forename: Kuniyoshi L
authors.initials: KL
authors.lastname: Sakai
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Okada
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iseki
mesh_terms: D000328:Adult; D001932:Brain Neoplasms / Q000601:surgery*; D002648:Child; D003399:Craniotomy; D005071:Evoked Potentials; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D019635:Neurosurgical Procedures / Q000379:methods; D013060:Speech / Q000502:physiology*; D014851:Wakefulness; D055815:Young Adult
keywords: CCEP = cortico-cortical evoked potentials; ECoG = electrocorticography; FLA = frontal language area; TLA = temporal language area; awake craniotomy; brain tumor; cortico-cortical evoked potentials; diagnostic and operative techniques; language function; oncology; surgery