Mapping without tasks: resting-state fMRI for motor and language localization in neuro-oncology.

PURPOSE: Presurgical functional mapping is essential for maximizing tumor resection while preserving motor and language function. While task-based fMRI (tb-fMRI) is the current non-invasive standard, its utility is substantially limited in patients with aphasia, paresis, or cognitive impairment who cannot comply with active paradigms. Resting-state fMRI (rs-fMRI) offers a task-free alternative, yet its spatial fidelity and clinical validity compared to task-based methods remain under rigorous evaluation. METHODS: In this prospective study, we evaluated 12 patients with histologically confirmed brain tumors who underwent rs-fMRI and tb-fMRI for preoperative sensorimotor and language mapping. Motor mapping utilized a bilateral finger tapping block-design paradigm. Language mapping utilized three distinct task paradigms (Silent Word Generation, Rhyming, and Synonym). Spatial concordance was quantified using Dice Similarity Coefficients (DSC), Jaccard Indices, and Receiver Operating Characteristic (ROC) analysis. RESULTS: rs-fMRI demonstrated fair to moderate spatial concordance with tb-fMRI. For motor mapping, the mean DSC was 0.62 ± 0.08 with high specificity (0.93 ± 0.02). In the language domain, rs-fMRI showed the highest concordance with the Silent Word Generation task (DSC 0.63 ± 0.11). Notably, rs-fMRI exhibited superior signal stability, with significantly fewer motion-censored volumes compared to language task paradigms (p < 0.01). While rs-fMRI demonstrated moderate sensitivity (~ 0.62), it achieved high specificity (0.93-0.94) across all domains however the moderate sensitivity indicates that functionally important regions may remain undetected. CONCLUSIONS: In this preliminary single-center study, rs-fMRI demonstrates fair to moderate spatial concordance with tb-fMRI and high specificity in delineating core eloquent cortex, though with moderate sensitivity that may leave functionally important regions undetected. The study provides hypothesis-generating evidence supporting the integration of rs-fMRI into multimodal presurgical workflows for neuro-oncology patients who cannot comply with task-based paradigms.