Cognitive Profiles and Determinants of Eligibility for Awake Surgery in Non-Dominant Hemisphere Gliomas: A Narrative Review

Background: Awake surgery has become a crucial approach in glioma treatment, primarily aimed at maximizing tumor resection while preserving neurological functions. While its application to the dominant hemisphere has been well established, its use in the non-dominant hemisphere remains underexplored. The non-dominant hemisphere plays essential roles in visuospatial processing, social cognition, and executive functions, which can significantly impact a patient's quality of life. Despite increasing evidence of these functions, standardized protocols for intraoperative brain mapping (ioBM) in the non-dominant hemisphere are lacking. Methods: A systematic search of the PubMed database was conducted to identify studies published between 2015 and 2024 that examined cognitive outcomes and ioBM paradigms in awake surgery for right non-dominant hemisphere gliomas. The review included studies that assessed neuropsychological outcomes, tumor characteristics, and the extent of surgical resection. Exclusion criteria included case reports, reviews, and studies focused exclusively on dominant hemisphere gliomas. A total of 13 studies met the inclusion criteria. Results: The review identified key cognitive functions assessed during awake surgery, including speech/motor language, visuospatial cognition, executive functions, social cognition, working memory, and sensorimotor functions. Intraoperative neuropsychological assessment primarily used cortical and subcortical stimulation, with a variety of cognitive tests applied to different domains. Studies reported that direct electrical stimulation (DES) revealed functional roles for the right hemisphere in visuospatial attention, social cognition, and executive functions. Patients who underwent awake surgery demonstrated better long-term cognitive outcomes and extended tumor resection compared to those under general anesthesia. However, variability in assessment tools and inconsistent reporting of postoperative outcomes were noted. Conclusion: Awake surgery combined with ioBM appears to be a viable approach for optimizing tumor resection while preserving cognitive functions in the non-dominant hemisphere. However, the lack of standardized cognitive assessment protocols remains a significant challenge. Future research should focus on establishing a unified set of cognitive tests for intraoperative assessment, conducting longitudinal studies on cognitive recovery, and integrating advanced neuroimaging techniques to refine surgical mapping. Standardizing intraoperative cognitive evaluations will be essential to improving patient outcomes and expanding the application of awake surgery for non-dominant hemisphere gliomas.