INSULAR gliomas can be resected safely with mapping, with low morbidity across 500 surgical cases.
Maximum Safe Resection In Insular Gliomas
Maximum safe resection remains a robust surgical strategy for insular gliomas, according to outcomes from a single center retrospective analysis of 502 resections performed in 394 unique patients between September 1997 and December 2022.
The study evaluated newly diagnosed and recurrent low grade gliomas and high grade gliomas involving the insula, a region that presents distinct operative challenges because of its proximity to critical vascular structures and functional brain regions. Using a transcortical approach supported by cortical and subcortical language and motor stimulation mapping, the analysis assessed tumor characteristics, extent of resection, postoperative morbidity, progression free survival, and overall survival.
Surgical Outcomes And Functional Risk
The cohort included 316 newly diagnosed cases, comprising 165 low grade gliomas and 151 high grade gliomas, and 186 recurrent cases, comprising 69 low grade gliomas and 117 high grade gliomas. Grade 2 gliomas were typically larger than grade 4 IDH wildtype gliomas, with median volumes of 43 cm³ versus 17.5 cm³.
Persistent postoperative motor and language deficits were uncommon in newly diagnosed grade 2 insular gliomas, occurring in fewer than 4% of cases. Transient deficits were more frequent, with transient motor deficits reported in 9.5% of cases and transient language deficits in 20%. Across the overall cohort, surgical and medical complications occurred in fewer than 3% of cases.
Residual Tumor Volume Linked To Survival
For newly diagnosed grade 2 insular gliomas, overall survival improved when residual tumor volume was below 2.7 cm³. Minimizing residual tumor volume was also associated with longer progression free survival and overall survival in recurrent grade 2 insular gliomas.
In newly diagnosed IDH wildtype glioblastoma, contrast enhancing tumor extent of resection above 88.6% was associated with improved progression free survival and overall survival. However, functional preservation remained central to surgical benefit. New permanent arm or leg weakness was significantly associated with worse overall survival in multivariable analysis, with a hazard ratio of 2.06.
These findings support maximum safe resection with transcortical access and stimulation mapping as an effective approach for insular gliomas, balancing aggressive tumor removal with preservation of neurologic function.
Reference
Young JS et al. Maximum safe resection of insular gliomas: update on surgical outcomes from 500 cases. J Neurosurg. 2026;DOI: 10.3171/2025.12.JNS251889.
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