Surgery of insular nonenhancing gliomas: volumetric analysis of tumoral resection, clinical outcome, and survival in a consecutive series of 66 cases.

Abstract

Despite intraoperative technical improvements, the insula remains a challenging area for surgery because of its critical relationships with vascular and neurophysiological functional structures. To retrospectively investigate the morbidity profile in insular nonenhancing gliomas, with special emphasis on volumetric analysis of tumoral resection. From 2000 to 2010, 66 patients underwent surgery. All surgical procedures were conducted under cortical-subcortical stimulation and neurophysiological monitoring. Volumetric scan analysis was applied on T2-weighted magnetic resonance images (MRIs) to establish preoperative and postoperative tumoral volume. The median preoperative tumor volume was 108 cm. The median extent of resection was 80%. The median follow-up was 4.3 years. An immediate postoperative worsening was detected in 33.4% of cases; a definitive worsening resulted in 6% of cases. Patients with extent of resection of > 90% had an estimated 5-year overall survival rate of 92%, whereas those with extent of resection between 70% and 90% had a 5-year overall survival rate of 82% (P < .001). The difference between preoperative tumoral volumes on T2-weighted MRI and on postcontrast T1-weighted MRI ([T2 - T1] MRI volume) was computed to evaluate the role of the diffusive tumoral growing pattern on overall survival. Patients with preoperative volumetric difference < 30 cm demonstrated a 5-year overall survival rate of 92%, whereas those with a difference of > 30 cm had a 5-year overall survival rate of 57% (P = .02). With intraoperative cortico-subcortical mapping and neurophysiological monitoring, a major resection is possible with an acceptable risk and a significant result in the follow-up.