Surgery of Insular Diffuse Gliomas - Part 2: Probabilistic Cortico-Subcortical Atlas of Critical Eloquent Brain Structures and Probabilistic Resection Map during Transcortical Awake Resection

BACKGROUND: Insular diffuse glioma surgery is challenging, and tools to help surgical planning could improve the benefit-to-risk ratio. OBJECTIVE: To provide a probabilistic resection map and frequency atlases of critical eloquent regions of insular diffuse gliomas based on our surgical experience. METHODS: We computed cortico-subcortical "eloquent"anatomic sites identified intraoperatively by direct electrical stimulations during transcortical awake resection of insular diffuse gliomas in adults. RESULTS: From 61 insular diffuse gliomas (39 left, 22 right; all left hemispheric dominance for language), we provided a frequency atlas of eloquence of the opercula (left/right; pars orbitalis: 0%/5.0%; pars triangularis: l5.6%/4.5%; pars opercularis: 37.8%/27.3%; precentral gyrus: 97.3%/95.4%; postcentral and supramarginal gyri: 75.0%/57.1%; temporal pole and superior temporal gyrus: 13.3%/0%), which tailored the transcortical approach (frontal operculum to reach the antero-superior insula, temporal operculum to reach the inferior insula, parietal operculum to reach the posterior insula). We provided a frequency atlas of eloquence identifying the subcortical functional boundaries (36.1% pyramidal pathways, 50.8% inferior fronto-occipital fasciculus, 13.1% arcuate and superior longitudinal fasciculi complex, 3.3% somatosensory pathways, 8.2% caudate and lentiform nuclei). Vascular boundaries and increasing errors during testing limited the resection in 8.2% and 11.5% of cases, respectively. We provided a probabilistic 3-dimensional atlas of resectability. CONCLUSION: Functional mapping under awake conditions has to be performed intraoperatively in each patient to guide surgical approach and resection of insular diffuse gliomas in right and left hemispheres. Frequency atlases of opercula eloquence and of subcortical eloquent anatomic boundaries, and probabilistic 3-dimensional atlas of resectability could guide neurosurgeons.