Intraoperative 5-aminolevulinic-acid-induced fluorescence in meningiomas

5-aminolevulinic acid (5-ALA) has gained importance as an intraoperative photodynamic diagnostic agent for the extirpation of malignant gliomas. The application of this technique for resection of meningiomas has barely been explored. The aim of this study was to evaluate the utility of 5-ALA-induced fluorescence as a visual tool in meningioma resection and its correlation with histological findings. A total of 33 consecutive patients undergoing resection of intracranial meningiomas from December 2007 to August 2009 were included in this study. After confirmation of normal liver function, 5-ALA was administered orally (20 mg/kg) within 3-5 h prior to skin incision. All cases were operated on using standard microsurgical and neuronavigation-guided techniques. Intraoperative 440 nm fluorescence was applied periodically during and at the end of resection in order to detect tumor-infiltrated sites. The fluorescence of the tumor was evaluated intraoperatively by the surgeon and confirmed by subsequent video analysis. A total of 32 (97%) patients presented with benign meningiomas (WHO I-II). In 1 (3%) patient, histological anaplastic signs (WHO III) could be demonstrated. 5-ALA-induced fluorescence of the tumor was confirmed in a total of 31 (94%) patients. The fluorescence did not correlate with the histological findings (n = 30 WHO I-II, n = 1 WHO grade III) or with preoperative brain edema and administration of steroids. A total resection could be postoperatively demonstrated in 25 (76%) patients. No adverse effects attributable to 5-ALA occurred. 5-ALA-induced fluorescence is a useful and promising intraoperative tool for the visualization of meningioma tissue. The novel findings demonstrated in this study in terms of high fluorescence and poor correlation with histological findings highlight the usefulness of this technique as a routine visual tool to achieve optimal resection of meningiomas.