- Researchers evaluated the safety and efficacy of the transcortical approach for resecting insular gliomas located near critical vascular and functional structures.
- This retrospective study analyzed 502 surgical cases involving 394 patients with newly diagnosed or recurrent low-grade and high-grade insular gliomas.
- For newly diagnosed grade 2 tumors, overall survival improved when residual volume was less than 2.7 cubic centimeters.
- The authors concluded that maximum safe resection using cortical mapping provides a robust strategy with low surgical morbidity.
- Clinicians should prioritize minimizing residual volume because permanent postoperative weakness significantly doubles the hazard ratio for mortality (HR 2.06).
Navigating the Functional and Vascular Complexity of Insular Gliomas
Surgical management of insular gliomas remains a significant clinical challenge due to the dense concentration of middle cerebral artery perforators and eloquent white matter tracts surrounding the insular cortex [1, 2]. While maximizing the extent of resection (the percentage of tumor volume removed) is the primary goal to improve survival and achieve seizure freedom, the optimal surgical route remains a subject of debate [3, 4]. The transsylvian approach (accessing the tumor through the natural opening of the Sylvian fissure) offers direct vascular visualization, whereas the transcortical approach (reaching the tumor through an incision in the overlying opercular cortex) may provide better access to certain tumor volumes with potentially fewer postoperative deficits [3, 5, 6]. To mitigate the risk of permanent neurological injury, neurosurgeons frequently utilize intraoperative adjuncts such as cortical and subcortical mapping, which uses electrical stimulation to identify and preserve functional brain tissue [7]. A recent retrospective study now offers precise volumetric targets and complication benchmarks to help clinicians balance aggressive resection with functional preservation.
A Longitudinal Analysis of 502 Insular Resections
The researchers conducted a retrospective analysis of 502 newly diagnosed and recurrent low-grade and high-grade gliomas of the insula. This extensive cohort included 394 unique patients who underwent surgical resection at a single center between September 1997 and December 2022. The study population was divided into 316 newly diagnosed cases (165 low-grade, 151 high-grade) and 186 recurrent cases (69 low-grade, 117 high-grade). By tracking outcomes over a 25-year period, the authors provided a high-powered assessment of how tumor grade and recurrence status influence surgical success. To standardize the anatomical data, the researchers classified tumors using the Berger-Sanai zone schema, a clinical system that divides the insula into four quadrants to guide surgical planning and predict morbidity. The extent of resection was calculated by manually segmenting contrast-enhancing and non-contrast-enhancing tumor volumes on magnetic resonance imaging. This volumetric analysis revealed that grade 2 gliomas were typically larger than grade 4 isocitrate dehydrogenase (IDH) wildtype gliomas, with median volumes of 43 cubic centimeters compared to 17.5 cubic centimeters (p < 0.001). IDH-wildtype status indicates a lack of the IDH mutation, a genetic profile characteristic of highly aggressive, traditional glioblastomas. These volumetric findings highlight the significant mass effect often associated with lower-grade insular lesions at presentation, reminding clinicians that slower initial growth patterns still culminate in substantial anatomical displacement.
Functional Preservation and Postoperative Morbidity
The surgical strategy utilized in this study relied on a transcortical approach combined with cortical and subcortical mapping, a technique involving direct electrical stimulation to identify functional pathways and eloquent brain regions during tumor removal. This method allows the surgeon to define the functional boundaries of the resection in real time, rather than relying solely on anatomical landmarks that are frequently distorted by the tumor mass. To ensure a comprehensive understanding of the long-term impact on patient quality of life, morbidity was assessed from the initial presentation to at least six months of follow-up. The researchers found that this mapping-guided approach maintained a high safety profile, as overall surgical and medical complications occurred in fewer than 3% of cases. Functional outcomes were particularly notable in the cohort of patients with newly diagnosed grade 2 tumors. In these cases, persistent postoperative motor and language deficits occurred in fewer than 4% of cases, demonstrating that permanent neurological impairment is rare when using rigorous subcortical mapping. However, the data indicate that transient neurological symptoms are a common part of the recovery process. Specifically, transient motor deficits occurred in 9.5% of cases and transient language deficits occurred in 20% of cases with newly diagnosed grade 2 tumors. For practicing physicians, these findings provide specific, evidence-based benchmarks for preoperative counseling, allowing them to accurately manage patient expectations regarding the high likelihood of temporary postoperative challenges versus the low risk of permanent disability.
Volumetric Thresholds for Survival and Prognosis
The clinical utility of the transcortical approach is defined by its ability to maximize tumor removal while respecting functional boundaries, a delicate balance that directly influences long-term oncological outcomes. To evaluate these outcomes, the researchers compared progression-free survival and overall survival using both unadjusted and propensity score-adjusted Kaplan-Meier and Cox regression analyses. Propensity score adjustment is a statistical technique used in observational studies to reduce selection bias by matching patients with similar baseline characteristics, while Cox regression estimates the effect of specific variables on the time it takes for an event like disease progression or death to occur. The data identified specific volumetric targets that neurosurgeons and oncologists can use to guide treatment goals. For patients with newly diagnosed grade 2 insular gliomas, overall survival was significantly improved when the residual tumor volume was reduced to less than 2.7 cubic centimeters. This emphasis on maximal cytoreduction extended to the recurrent setting as well, where minimizing residual tumor volume was associated with prolonged progression-free survival and overall survival for recurrent grade 2 insular gliomas. The study also established clear benchmarks for high-grade pathologies, which often present different surgical priorities than their low-grade counterparts. For patients with newly diagnosed IDH-wildtype glioblastoma, a contrast-enhancing tumor extent of resection greater than 88.6% was associated with improved progression-free survival and overall survival. These findings confirm that even within the complex anatomy of the insula, achieving specific resection thresholds provides a measurable survival benefit. However, the data also underscore the high cost of surgical morbidity. In multivariable analyses, the development of new permanent arm or leg weakness was significantly associated with worse overall survival (HR 2.06, 95% CI 1.14 to 3.74; p = 0.017). This doubling of the mortality risk highlights a critical clinical takeaway: while aggressive resection is highly beneficial, the preservation of motor function must remain the primary limiting factor during surgery to ensure long-term patient longevity.
References
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2. Papadopoulou A, Kumar NS. Prognostic Factors and Resectability Predictors in Insular Gliomas: A Systematic Review. Journal of Neurological Surgery Part A Central European Neurosurgery. 2023. doi:10.1055/s-0043-1769128
3. Irshad HA, Altaf A, Shakir M, et al. Transcortical versus Transsylvian Approach for Insular Gliomas: A Systematic Review and Meta-Analysis. Asian Journal of Neurosurgery. 2026. doi:10.1055/s-0046-1815955
4. Zhang JJ, Lee KS, Wang DD, Hervey‐Jumper SL, Berger MS. Seizure outcome after resection of insular glioma: a systematic review, meta-analysis, and institutional experience. Journal of neurosurgery. 2022. doi:10.3171/2022.8.jns221067
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