Incidentally discovered diffuse low-grade gliomas progress in a fashion similar to their symptomatic counterparts. Their early detection allows more effective pre-emptive and individualized oncological treatment. We assessed the safety and efficacy of maximal safe resection according to functional boundaries for incidental diffuse low-grade gliomas in eloquent areas.

Two-centre retrospective series of adult patients with incidental diffuse low-grade gliomas located within/close to eloquent areas in the dominant hemisphere, treated with maximal surgical resection according to functional boundaries under intraoperative functional cortico-subcortical monitoring under awake conditions, and with a minimal follow-up of 24months.

The series included 19 patients (8 men, 11 women) with no preoperative neurological deficit but with a radiologically enlarged glioma. No intraoperative seizure, postoperative infection, haematoma or wound-healing problem was observed. In the immediate postsurgical period, a transient neurological worsening occurred in 10 patients. The resection (mean rate 96.4%; range, 82.4–100) was supratotal in 5 cases, total in 5 cases, subtotal in 7 cases, and partial in 2 cases. Six months after surgery, all patients recovered after functional rehabilitation, with no permanent neurological deficit, Karnofsky Performance Status was 100 (except for one patient who received early postoperative radiotherapy) and no seizures were observed. The survival without progression requiring oncological treatment was significantly longer in patients with a total/supratotal resection than in patients with a partial/subtotal resection.

These results suggest the reproducibility, safety, and effectiveness of an early maximal functionally based resection within cortico-subcortical functional boundaries for incidental diffuse low-grade gliomas in adults in centres hyperspecialized in surgical neuro-oncology.