gms | German Medical Science

Objective: Fluorescence-guidance with 5-ALA helps improve resections of malignant gliomas. However, one limitation is the low intensity of blue light for background illumination. Fluorescein has recently been re-introduced into neurosurgery and novel microscope systems are available for visualizing this fluorochrome, which highlights all perfused tissues but has limited selectivity for tumor detection. We here investigate a combination of both fluorochromes, ALA for distinguishing tumor and fluorescein for providing tissue fluorescence of adjacent brain tissue.

Methods: We evaluated six patients with cerebral lesions suggestive of high-grade glioma. Patients received ALA (20mg/kg) orally four hours before induction of anesthesia. Low dose fluorescein (3mg/kg i.v.) was injected immediately after anesthesia induction. Zeiss Pentero microscopes (equipped either with Yellow560 or Blue400 filters) were used to visualize fluorescence. To simultaneously visualize both fluorochromes, the Yellow560 module was combined with external blue light illumination (Storz D-Light).

Results: Fluorescein-induced fluorescence created a useful background for protoporphyrin IX (PPIX) fluorescence, which appeared orange to red, surrounded by greenly fluorescent normal brain and edematous tissue. Green brain tissue fluorescence was helpful in augmenting background. Too strong levels of blue illumination obscured PPIX fluorescence. Unspecific extravasation of fluorescein was noted at resection margins, which did not interfere with PPIX fluorescence detection.

Conclusion: Dual labeling with both PPIX and fluorescein fluorescence is feasible and gives superior background information during fluorescence guided-resections. We believe this technique carries potential as a next step in fluorescence-guided resections if completely integrated into the surgical microscope.