The Transtemporal Isthmus Approach for Insular Glioma Surgery

BACKGROUND AND OBJECTIVES: Maximal and safe removal of insular gliomas by a transinsular cortex approach is challenging. In this article, a new transtemporal isthmus approach to resect insular gliomas is presented. METHODS: We retrospectively examined 53 patients with insular glioma who underwent resection through the temporal isthmus approach using magnetic resonance imaging and functional neuronavigation guidance and intraoperative electrophysiological monitoring. Extent of resection was determined using intraoperative magnetic resonance imaging. RESULTS: Fifty-three patients were included for analysis, 30 men and 23 women. The median (range) age was 45 (26-70) years. Tumor laterality was left in 22 patients and right in 31. All tumors involved at least zone III or IV (Berger-Sanai classification system), including zones I-IV were involved in 29 (54.7%) and zones III and IV in 17 (32.0%). Among the 37 low-grade gliomas, preoperative median (IQR) volume was 45.7 (31.8, 60.3) cm 3 , and gross total resection was achieved in 24 (64.9%). Among the 16 high-grade gliomas, preoperative median (IQR) volume was 45.3 (40.1, 54.0) cm 3 , and gross total resection was achieved in 14 (87.5%). The median (IQR) extent of resection of the whole group was 100% (89%-100%). The median (IQR) postoperative Karnofsky performance score 3 months after surgery was 90 (80-90). Mean temporal isthmus width was significantly higher in the affected side (involving tumor) than the contralateral one (21.6 vs 11.3 mm; 95% CI: 9.3 to 11.3, P < .01). Muscle strength was grade 4 or higher, and speech was nearly normal in all patients 3 months after surgery. CONCLUSION: Insular glioma surgery using the transtemporal isthmus approach can achieve safe and maximum resection. A widened temporal isthmus provides a surgical pathway for transisthmic resection of insular tumor.