Although one surgical study has shown fMRI for neurosurgical planning was a useful, comparing with intraoperative DCS during awake surgery 18, most studies have not clarified the reliability of language fMRI in preoperative neurosurgical planning for patients with tumors in language-eloquent brain regions 17, 19, 20, 21. Because a fMRI activation also represents excitatory activation, which is the result of having been recruited by an upstream or downstream area, there is a fundamental problem with fMRI to predict speech localization for presurgical planning. This technique has been widely used in preoperative risk assessment and planning to reduce the rate of post-surgical functional impairments 16, 17.
Language task-based functional magnetic resonance imaging (fMRI) allows preoperative non-invasive identification of language areas. Furthermore, the risk of postoperative language deficits significantly increases when brain tumor surgery involves the language dominant hemisphere it is therefore crucial to determine language dominance for surgical planning 14, 15. While intraoperative language mapping is highly reliable, preoperative language evaluation can be of great value because the investigation of cortical language functions preoperatively makes brain tumor surgery safe, practical, and effective. Intraoperative awake language mapping with direct cortical stimulation (DCS) is therefore advocated for the preservation of language function 11, 12, 13. However, gliomas often occur near or within functionally eloquent regions 9, 10, which means that tumor removal in such areas carries a potentially high risk for neurological function deficits, including motor dysfunction, language disturbance, and neurocognitive impairments. Numerous clinical studies have demonstrated that gross total resection or maximum extent of resection (EOR), such as maximum resection, significantly increase progression-free survival (PFS) and overall survival (OS) in patients with gliomas 1, 3, 4, 5, 6, 7, 8.
The first-line treatment for low- and high-grade gliomas is extensive surgical resection 1, 2, 3. Our findings suggest that nrTMS language mapping could be a reliable method, particularly in obtaining responses for cases without tumor-involvement of classical perisylvian language areas. Based on the receiver operating curve statistics, subgroup analysis showed that the non-involvement of language-related regions afforded significantly better the area under the curve (AUC) values (AUC = 0.81, 95% confidence interval (CI): 0.74–0.88) than the involvement of language-related regions (AUC = 0.58, 95% CI: 0.50–0.67 p < 0.0001).
We then investigated how some parameters, including age, tumor type, tumor volume, and the involvement of anatomical language-related regions, affected different subpopulations. In the 50 patients with left-side gliomas, nrTMS language mapping showed 81.6% sensitivity, 59.6% specificity, 78.5% positive predictive value, and 64.1% negative predictive value when compared with the respective DCS values for detecting language sites in all regions. The tumor was located in the left and right hemisphere in 50 (82.0%) and 11 (18.0%) patients, respectively. Sixty one patients were enrolled, and this study included 42 low-grade gliomas and 19 high-grade gliomas (39 men, 22 women mean age, 41.1 years, range 18-72 years). In the prospective, non-randomized study, patients had to meet all of the following inclusion criteria: the presence of left- or right-side brain tumors in the vicinity of or inside the areas anatomically associated with language functions awake brain surgery scheduled and age >18 years. We aimed to investigate clinical parameters that affected the results of navigated repetitive transcranial magnetic stimulation (nrTMS) language mapping by comparing the results of preoperative nrTMS language mapping with those of direct cortical stimulation (DCS) mapping.