A series of 309 awake surgeries with transcortical approach for IDH-mutant low-grade glioma involving the insula: long-term onco-functional outcomes in 253 consecutive patients

OBJECTIVE: In low-grade glioma (LGG), awake surgery (AS) with intraoperative functional mapping minimizes morbidity while increasing the extent of resection (EOR). However, the actual role of AS for insular LGG resection through the opercula is still debated. The aim of this study was to investigate the long-term results after AS via a transcortical approach in patients with LGG within the insula, and to compare outcomes between pure insular gliomas and gliomas also invading other lobes. METHODS: Patients who underwent AS with functional-based resection via the opercula performed by the author for an isocitrate dehydrogenase-mutant grade 2 glioma involving the insula were selected (June 2002-January 2024). Functional and oncological outcomes were analyzed by comparing pure insular gliomas (group 1) versus insular-centered gliomas also involving the frontal and/or temporal and/or parietal lobes (group 2). RESULTS: In this consecutive cohort, 309 ASs were achieved in 253 patients (132 men [52.2%], mean age 37.5 ± 9.5 years). Among 214 patients (84.5%) with epilepsy before surgery, 55 had intractable seizures (21.7%). The preoperative mean Karnofsky Performance Scale score was 93.1 ± 7.4, with 206 patients (81.4%) working before surgery. The series included 147 left-sided gliomas (58.1%), with a mean preoperative tumor volume for both sides of 70.1 ± 50.1 cm3 with 39 total tumors (15.4%) in group 1 and 214 total tumors (84.6%) in group 2. No patients except 2 (99.2%) had a permanent postoperative deficit (mean Karnofsky Performance Scale score 93 ± 6.6), with 199 patients returning to work (96.6%). Only 20 patients (7.9%) continued to suffer from intractable epilepsy. The mean EOR was 89.4% ± 8.4% (mean residual tumor volume: 9.6 ± 13.1 cm3). There were 166 astrocytomas (65.6%) and 87 oligodendrogliomas (34.4%). Fifty-three patients (20.9%) received immediate postoperative adjuvant therapy and 49 patients (19.3%) underwent subsequent AS. The mean follow-up was 7.1 ± 3.9 years, with an overall survival rate of 80.2% (203 patients were still alive at last evaluation). More patients had an incidental glioma in group 1 (p = 0.00009), whereas there was a higher rate of intractable seizures (p = 0.0019) and a greater tumor volume before surgery in group 2 (p < 0.00001). Nonetheless, the EOR and the rate of postoperative intractable seizures were similar in both groups, with more patients in group 2 resuming work (p = 0.001). CONCLUSIONS: This is the largest homogeneous surgical experience of LGGs involving the insula that were resected through the opercula based on awake mapping. The results show a high percentage of functional preservation and return to work, with a high overall survival rate.