Role of intraoperative neurophysiological monitoring during fluorescence-guided resection surgery

Fluorescence-guided resection (FGR) using 5-aminolevulinic acid (5-ALA) exhibits a potential risk of permanent neurological deficits that can be minimized using intraoperative neurophysiological monitoring (IONM). We assessed the role of IONM in FGR surgery in patients harboring tumors in or near eloquent areas.

IONM and FGR surgeries were performed on 34 patients (49.8 ± 2.4 years) harbored malignant primary gliomas near eloquent cortical areas or semioval center. Different combinations of neurophysiological techniques were used depending on each patient.

Gross total resection (GTR) was achieved in 66.7 % of the patients, mean 90.4 ± 3.7 % without neurological deficits. Resection in four patients was stopped by the occurrence of severe warning criteria despite the presence of fluorescence. Hemispheric transcranial electrical stimulation was safe and confident even in cortical surgery. Notably, a significant percentage of patients exhibited clinical improvement after the surgery. One week after surgery, only one patient worsened, and seven patients improved. At 3 months, 27.8 % of the patients improved, and the other patients maintained a similar status to their pre-surgery condition. Warning common criteria (amplitude reduction and/or latency increase) appeared in 68.2 and 50.0 % of patients during cortical or semioval surgery, respectively, with neither a false-negative nor a false-positive clinical outcome. Although 5-ALA exhibits phototoxicity, VEP did not induce any secondary effects in the visual system, including eyelids.

IONM can be helpful during surgery to maximize the tumor resection, meanwhile help to avoid neurological deficits and, therefore, to improve the quality of life of these patients.