title: Passive language mapping combining real-time oscillation analysis with cortico-cortical evoked potentials for awake craniotomy.
abstract: OBJECTIVE Electrocortical stimulation (ECS) is the gold standard for functional brain mapping; however, precise functional mapping is still difficult in patients with language deficits. High gamma activity (HGA) between 80 and 140 Hz on electrocorticography is assumed to reflect localized cortical processing, whereas the cortico-cortical evoked potential (CCEP) can reflect bidirectional responses evoked by monophasic pulse stimuli to the language cortices when there is no patient cooperation. The authors propose the use of "passive" mapping by combining HGA mapping and CCEP recording without active tasks during conscious resections of brain tumors. METHODS Five patients, each with an intraaxial tumor in their dominant hemisphere, underwent conscious resection of their lesion with passive mapping. The authors performed functional localization for the receptive language area, using real-time HGA mapping, by listening passively to linguistic sounds. Furthermore, single electrical pulses were delivered to the identified receptive temporal language area to detect CCEPs in the frontal lobe. All mapping results were validated by ECS, and the sensitivity and specificity were evaluated. RESULTS Linguistic HGA mapping quickly identified the language area in the temporal lobe. Electrical stimulation by linguistic HGA mapping to the identified temporal receptive language area evoked CCEPs on the frontal lobe. The combination of linguistic HGA and frontal CCEPs needed no patient cooperation or effort. In this small case series, the sensitivity and specificity were 93.8% and 89%, respectively. CONCLUSIONS The described technique allows for simple and quick functional brain mapping with higher sensitivity and specificity than ECS mapping. The authors believe that this could improve the reliability of functional brain mapping and facilitate rational and objective operations. Passive mapping also sheds light on the underlying physiological mechanisms of language in the human brain.
authors.affiliation: Department of Neurosurgery and.
authors.forename: Yukie
authors.initials: Y
authors.lastname: Tamura
authors.affiliation: Department of Neurosurgery and.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ogawa
authors.affiliation: Guger Technologies OG, Graz, Austria; and.
authors.forename: Christoph
authors.initials: C
authors.lastname: Kapeller
authors.affiliation: Guger Technologies OG, Graz, Austria; and.
authors.forename: Robert
authors.initials: R
authors.lastname: Prueckl
authors.affiliation: Center for Advanced Research and Education, School of Medicine, Asahikawa Medical University, Hokkaido, Japan.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Takeuchi
authors.affiliation: Department of Neurosurgery and.
authors.forename: Ryogo
authors.initials: R
authors.lastname: Anei
authors.affiliation: Department of Neurology, Albany Medical Center, Albany, New York.
authors.forename: Anthony
authors.initials: A
authors.lastname: Ritaccio
authors.affiliation: Guger Technologies OG, Graz, Austria; and.
authors.forename: Christoph
authors.initials: C
authors.lastname: Guger
authors.affiliation: Department of Neurosurgery and.
authors.forename: Kyousuke
authors.initials: K
authors.lastname: Kamada
mesh_terms: D000328:Adult; D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D001932:Brain Neoplasms / Q000601:surgery*; D003399:Craniotomy / Q000379:methods*; D005071:Evoked Potentials; D005260:Female; D005625:Frontal Lobe; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D013702:Temporal Lobe; D014851:Wakefulness
keywords: BIS = bispectral index; CCEP = cortico-cortical evoked potential; ECS = electrocortical stimulation; ECoG = electrocorticography; ERD, ERS = event-related desynchronization, event-related synchronization; HGA = high gamma activity; PN = picture naming; WR = word reading; awake craniotomy; corticocortical evoked potentials; diagnostic and operative techniques; electrocortical stimulation; electrocorticography; fMRI = functional MRI; high gamma activity; language