gms | German Medical Science

Objective: For skull base meningiomas as well as for malignant meningiomas an accurate discrimination between tumor and normal brain tissue is essential to achieve complete resection. In glioma surgery the role of 5-ALA fluorescence guided resection is well established. There are several reports about the use of 5-ALA for meningiomas. We present our current observations on the utility of 5-ALA for the resection of meningiomas.

Methods: Between 03/2010 and 11/2011 5-ALA was administered to a total of 42 patients with meningiomas 3–4 h prior to operation. The fluorescence was evaluated at the beginning, during and at the end of tumor resection. The intensity was classified by the surgeon into no, low or extensive fluorescence intensity as compared to aspects in malignant gliomas. After estimated complete resection the resection cavity was inspected with blue light (440 nm) to detect any residual tumor tissue.

Results: A total of 32 meningiomas were analysed in this trial. 19 showed histological findings of WHO I, 8 of WHO II and 5 of WHO III meningiomas. In 29 meningiomas a varying intensity of fluorescence was observed. 3 tumors showed no fluorescence. In 16 meningiomas the fluorescence intensity was similar to those in malignant gliomas. In the remaining 13 cases the intensity was low and similar to the intensity of the infiltration zone in malignant gliomas. The fluorescence did not correlate with histological findings or localization. In malignant meningiomas an infiltration of normal brain tissue was detected commonly by 5-ALA induced fluorescence. The difference was significant (p = 0,043). Among the ALA + meningiomas a complete resection was performed in 24 meningiomas whereas in 5 meningiomas only a subtotal resection could be achieved. In 25 cases the resection grade was documented by the surgeon's impression and confirmed by an early postoperative MRI scan within 72 hours.

Conclusions: 5-ALA induced protoporphyrin IX fluorescence seems to be useful to visualize meningioma tumor tissue. In benign, circumscribed convexity meningiomas a high rate of complete resection could be achieved without fluorescence guidance. However, in skull base, parasagittal and higher grade meningiomas residual tumor infiltration may be detected. There are differences in fluorescence intensity, But in contrast to gliomas fluorescence intensity is not correlated to malignancy. The results are too preliminary to conclude whether 5-ALA may decrease the rates of recurrence and improve clinical outcome.