title: Intraoperative dorsal language network mapping by using single-pulse electrical stimulation.
abstract: The preservation of language function during brain surgery still poses a challenge. No intraoperative methods have been established to monitor the language network reliably. We aimed to establish intraoperative language network monitoring by means of cortico-cortical evoked potentials (CCEPs). Subjects were six patients with tumors located close to the arcuate fasciculus (AF) in the language-dominant left hemisphere. Under general anesthesia, the anterior perisylvian language area (AL) was first defined by the CCEP connectivity patterns between the ventrolateral frontal and temporoparietal area, and also by presurgical neuroimaging findings. We then monitored the integrity of the language network by stimulating AL and by recording CCEPs from the posterior perisylvian language area (PL) consecutively during both general anesthesia and awake condition. High-frequency electrical stimulation (ES) performed during awake craniotomy confirmed language function at AL in all six patients. Despite an amplitude decline (≤32%) in two patients, CCEP monitoring successfully prevented persistent language impairment. After tumor removal, single-pulse ES was applied to the white matter tract beneath the floor of the removal cavity in five patients, in order to trace its connections into the language cortices. In three patients in whom high-frequency ES of the white matter produced naming impairment, this "eloquent" subcortical site directly connected AL and PL, judging from the latencies and distributions of cortico- and subcortico-cortical evoked potentials. In conclusion, this study provided the direct evidence that AL, PL, and AF constitute the dorsal language network. Intraoperative CCEP monitoring is clinically useful for evaluating the integrity of the language network.
authors.affiliation: Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Yamao
authors.forename: Riki
authors.initials: R
authors.lastname: Matsumoto
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kunieda
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Arakawa
authors.forename: Katsuya
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Kiyohide
authors.initials: K
authors.lastname: Usami
authors.forename: Sumiya
authors.initials: S
authors.lastname: Shibata
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Nobukatsu
authors.initials: N
authors.lastname: Sawamoto
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Mikuni
authors.forename: Akio
authors.initials: A
authors.lastname: Ikeda
authors.forename: Hidenao
authors.initials: H
authors.lastname: Fukuyama
authors.forename: Susumu
authors.initials: S
authors.lastname: Miyamoto
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery*; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D003399:Craniotomy / Q000379:methods; D056324:Diffusion Tensor Imaging; D004558:Electric Stimulation / Q000379:methods*; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D007802:Language; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology / Q000502:physiology; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome; D066127:White Matter / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D055815:Young Adult
keywords: arcuate fasciculus; awake craniotomy; cortico-cortical evoked potential; dorsal language network; subcortico-cortical evoked potential