Use of 5-ALA for Meningioma Surgery: New Concepts of Total Resection

Introduction: Meningiomas complete resection can be curative. Recurrence, however, may occur even after a Simpson I—macroscopically complete removal of tumor. The reason may be remnant tumor cells that are not perceived by the surgeon after complete macroscopic resection. 5-aminolevulinic acid (5-ALA) has been routinely used during resection of gliomas all around the world in the last years. This special colorant has become an indispensable tool in the most part of surgeries of this kind. Several meningiomas showed to be 5-ALA positive, and the fluorescence-guided resections of these tumors could probably be improved with this technique.

Objective: Evaluate the possible advantages of the use of the 5-ALA during meningioma surgery and reconsider the total resection concept.

Methods: Patients with meningiomas in different locations were selected for this study. After administration of 5-ALA, patients were operated on aiming complete tumor resection. After tumor removal, the final inspection using the FL400 microscope filter was performed, and remnant 5-ALA-positive cells were looked for and further removed when found. Additionally, a detailed histological and immunohistochemical study of the tumors was performed.

Results: Tumor was 5-ALA positive in three cases. Remnant 5-ALA-positive cells were found in one case after total resection was presumed under the evaluation with the regular microscope. The 5-ALA-positive tissue could be completely removed. This technique enabled a “more complete” resection of the meningioma probably reducing the chances of a recurrence.

Conclusion: The use of 5-ALA and the FL400 filter for meningioma surgeries seem to improve the resection rate of tumor in some cases. This can probably reduce the chances of a recurrence in totally removed tumors with additionally 5-ALA free resections. These findings could also eventually explain the recurrence rates reported in the literature for Simpson I—macroscopically completely removed tumors. A new resection grade classification is proposed.

Fig. 1 Operative field after resection of a calcified parasagittal meningioma (arrows showing remnant 5-ALA-positive tissue). Left: regular microscope view, Right: FL400 filter.