Endoscopic 5-Aminolevulinic Acid- Induced Fluorescence-Guided Intraparenchymal Brain Tumor Resection-Can the Endoscope Detect More Fluorescence Than the Microscope?

- OBJECTIVES: Using a laboratory-based optical setup, we show that 5-aminolevulinic acid (5ALA) fluorescence is better detected using the endoscope than the microscope. Furthermore, we present our case series of fully endoscopic 5ALA-guided resection of intraparenchymal tumors. - METHODS: A Zeiss Pentero microscope was compared with the Karl Storz Hopkins endoscope. The spectra and intensity of each blue light source were measured. Quantitative fluorescence detection thresholds were measured using a spectrometer. Subjective fluorescence detection thresholds were measured by 6 blinded neuro-oncology surgeons. Clinical data were prospectively collected for all consecutive cases of fully endoscopic 5ALA-guided resection of intraparenchymal tumors between 2012 and 2023. - RESULTS: The intensity of blue light on the sample was greater for the endoscope than the microscope at working distances less than 20 mm. The quantitative fluorescence detection thresholds were lower for the endoscope than the microscope at both 30-/10-mm working distances. Fluorescence detection threshold was 0.65%- 0.80% relative 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyranthe concentration (3.20 x 10- 7 to 3.94 x 10- 7 mol/dm- 3 ) for the microscope, 0.40%- 0.55% relative concentrations (1.97 x 10- 7 to 2.71 x 10- 7 mol/dm- 3 ) for the endoscope at 30 mm, and 0.15%- 0.30% relative concentrations (7.40 x 10- 8 to 1.48 x 10- 7 mol/dm- 3 ) for the endoscope at 10 mm. In total, 49 5ALA endoscope-assisted brain tumor resections were carried out on 45 patients (mean age = 41 years, male = 28). Greater than 95% resection was achieved in 80% of cases and gross total resection in 42%. Gross total resection was achieved in 100% of tumors in noneloquent locations. There was 1 new neurologic deficit. - CONCLUSIONS: The endoscope provides enhanced visualization/detection of 5ALA-induced fluorescence compared with the microscope. 5ALA endoscopic-assisted resection of intraparenchymal tumors is safe and feasible.