Resection of malignant brain tumors in eloquent cortical areas: A new multimodal approach combining 5-aminolevulinic acid and intraoperative monitoring

Object. Several studies have revealed that the gross-total resection (GTR) of malignant brain tumors has a significant influence on patient survival. Frequently, however, GTR cannot be achieved because the borders between healthy brain and diseased tissue are blurred in the infiltration zones of malignant brain tumors. Especially in eloquent cortical areas, resection is frequently stopped before total removal is achieved to avoid causing neurological deficits. Interestingly, 5-aminolevulinic acid (5-ALA) has been shown to help visualize tumor tissue intraoperatively and, thus, can significantly improve the possibility of achieving GTR of primary malignant brain tumors. The aim of this study was to go one step further and evaluate the utility and limitations of fluorescence-guided resections of primary malignant brain tumors in eloquent cortical areas in combination with intraoperative monitoring based on multimodal functional imaging data. Methods. Eighteen patients with primary malignant brain tumors in eloquent areas were included in this prospective study. Preoperative neuroradiological examinations included MR imaging with magnetization-prepared rapid gradient echo (MPRAGE), functional MR, and diffusion tensor imaging sequences to visualize functional areas and fiber tracts. Imaging data were analyzed offline, loaded into a neuronavigational system, and used intraoperatively during resections. All patients received 5-ALA 6 hours before surgery. Fluorescence-guided tumor resections were combined with intraoperative monitoring and cortical as well as subcortical stimulation to localize functional areas and fiber tracts during surgery. Results. Twenty-five procedures were performed in 18 consecutive patients. In 24% of all surgeries, resection was stopped because a functional area or cortical tract was identified in the resection area or because motor evoked potential amplitudes were reduced in an area where fluorescent tumor cells were still seen intraoperatively. Gross-total resection could be achieved in 16 (64%) of the surgeries with preservation of all functional areas and fiber tracts. In 2 patients presurgical hemiparesis became accentuated postoperatively, and 1 of these patients also suffered from a new homonymous hemianopia following a second resection. Conclusions. The authors' first results show that tumor resections with 5-ALA in combination with intraoperative cortical stimulation have the advantages of both methods and, thus, provide additional safety for the neurosurgeon during resections of primary malignant brain tumors in eloquent areas. Nonetheless, more cases and additional studies are necessary to further prove the advantages of this multimodal strategy.