[Intraoperative cortical mapping in the surgical resection of low-grade gliomas located in eloquent areas]

Surgical selection of patients harboring low-grade gliomas based on radiological criteria may be insufficient due to individual variability in eloquent areas location and to the fact that function can be preserved within infiltrated brain tissue. Brain stimulation mapping safety for patients with low-grade gliomas is evaluated, analyzing whether this technique modifies the extent of resection and minimizes postoperative deficits.

Twenty-five patients with lowgrade gliomas (II/IV WHO) located in eloquent areas underwent tumor resection with the aid of intraoperative mapping. Patients underwent surgery under local or general anesthesia depending on the neurological function to be explored. All procedures were performed from an oncological point of view, trying to achieve a radical tumor resection but stopping removal whenever functional tissue was found within or near the lesion.

Total or subtotal resection was achieved in 16 patients (64%); in five cases (20%) resection was partial, and in the remaining (16%) only a biopsy was obtained. Tumors located in the supplementary motor area (SMA) or in the operculum were those which could be more often totally resected. Thirteen patients (52%) experienced neurological worsening immediately after surgery but eight of them had almost completely recovered six months after the procedure.

Intraoperative functional mapping can optimize extent of resection minimizing permanent morbidity. Functional tissue can be found within the infiltrated brain and this must be considered in the presurgical planning. SMA and opercular tumors allow radical resection with low morbidity whereas insular tumors remain a challenge even with the aid of this technique.