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.

Single pulse electrical stimulation to probe functional and pathological connectivity in epilepsy

“…Both effective and anatomical connectivity studies complemented each other to establish the contemporary connections within the dorsal language stream. The CCEP connectivity pattern in the dorsal language stream has been consistently reported by other groups [15, 24, 27, 34, 35] [28]. In addition, a series of language CCEP studies demonstrated bidirectional connections between AL and PL through AF, which has been traditionally considered as a unidirectional pathway from PL to AL (Wernicke-Geschwind model) in the 20th century.…”

“…CCEP recording is highly practical because 1) the subjects are not requested to perform any specific task, just lying or sitting on a bed and 2) cortico-cortical connectivity can be probed with directionality information from one stimulus site within a minute. Because of its high practicality and feasibility during general anesthesia, CCEPs are now applied in the intraoperative setting to monitor functional brain networks such as language[26] [27, 28]. …”

“…Intraoperative CCEP monitoring is clinically feasible for evaluating the integrity of the dorsal language network. This intraoperative method has been introduced successfully in other institutes[27, 28] and was combined with other methods such as high gamma activity mapping during receptive language tasks[28]. Enrollment of a larger number of patients is warranted to establish its clinical utility.…”

Functional differences among stimulation-identified cortical naming sites in the temporal region

“…Emerging work in diffusion tensor imaging (DTI) and cortico-cortical evoked potentials (CCEPs) underscores the need to consider these results in the context of a more diffuse language network that encompasses both cortical and subcortical areas [25-28]. Thus, these topographical findings likely reflect, not localization of semantic or phonological functions, but rather, cortical locations where disruption of a broader network produces impairments in a reliable manner.…”

Development of information sharing in language neocortex in childhood‐onset drug‐resistant epilepsy

“…[8][9][10] Generally, the topography of language-related HGM has been comparable between children and adults. 1,[11][12][13][14][15] However, age of the patient is an important determinant of postoperative seizure and language outcomes after epilepsy surgery. [16][17][18] There is a paucity of data about the impact of age on network properties of language-related HGM.…”