JS05.6.A CONTINUOUS DYNAMIC MAPPING OF LANGUAGE FUNCTION AND COGNITIVE CONTROL AND SPATIAL CORRELATION TO WHITE MATTER TRACTS USING INTRAOPERATIVE MRI TRACTOGRAPHY

Abstract

Abstract BACKGROUND Subcortical mapping of white matter tracts (WMTs) subserving complex processes as movement, language and cognition is critical in glioma surgery. Continuous dynamic mapping (CDM) is an indispensable tool for mapping of the corticospinal tract (CST). There is, however, no widespread method for CDM of more advanced brain functions. MATERIAL AND METHODS Patients undergoing awake craniotomy for diffuse gliomas at the Oslo University Hospital with the use of neuronavigation, diffusion tensor imaging (DTI) and CDM coupled with structured evaluation as well as intraoperative magnetic resonance imaging (iMRI) were included in a retrospective analysis. Subcortical CDM was conducted when resection became close to the arcuate fasciculus (AF) and the frontal aslant tract (FAT) with clinical testing using language paradigms and Stroop task. The current was delivered through a monopolar suction probe applying a modified Taniguchi technique with short train of pulses. The spatial relationship between the stimulation response and the examined tracts was determined by measuring the shortest distance between the resection cavity and the relevant white matter tracts (WMTs) using iMRI DTI. RESULTS Twenty IDH-mutant and eight IDH wild type gliomas operated 2021-2023 were included in the analysis. Subcortical CDM of the AF and the FAT proved to be amenable as both language function and the ability to perform Stroop test were affected when the stimulation site gradually became close (< 1 cm) to the examined tracts. Positive stimulation response was verified by repeat challenge. The stimulation intensity was thereafter reduced in a stepwise fashion when there was a consistent hesitation in the patient’s response. Resection was continued until the tumor border was reached and not beyond the threshold of 3mA. The threshold of stimulation intensity correlated to the minimal distance from the resection cavity to the delineated WMTs. We did not observe any seizure activity induced by CDM. CONCLUSION We have experienced subcortical CDM to be a safe and reliable method, where distance to identified WMT appear to be correlated to the applied stimulation intensity.