Sodium Fluorescein-Guided Surgery in Peripheral Nerve Sheath Tumors: First Experience in 10 Cases of Schwannoma

BACKGROUND: The intravenous application of sodium fluorescein (SF) for brain tumor surgery goes back to the late 1940s. The development of specific fluorophore filters significantly reduced the required dosage of SF and therefore diminished possible side effects. This study investigates the application of SF in benign peripheral nerve sheath tumors (PNSTs), concentrating on its feasibility during microsurgical removal. METHODS: The single-center study includes 10 consecutive schwannoma cases operated on between September 2016 and March 2017. Inclusion criteria were defined as age >= 18 years, preoperative magnetic resonance imaging with suspicion of schwannoma, and final histopathologic confirmation of schwannoma. Exclusion criteria were a history of intolerance to SF and renal insufficiency. The microsurgical part of each surgery was video recorded, and the collected material was retrospectively analyzed. Red, green, and blue values of various regions of interest set on tumor and normal nerve of each patient were evaluated using ImageJ, an open platform for scientific image analysis. RESULTS: Digital video analysis confirmed the intra-operative impression of increased fluorescence of the tumor in contrast with normal nerve tissue. Because the color yellow is predominantly a mixture of red and green, values of these colors were significantly increased in schwannomas compared with normal nerve tissue ( P = 0.0003 and P = 0.0023, respectively). CONCLUSIONS: SF reveals increased fluorescence in schwannomas compared with normal nerve tissue. Intraoperative differentiation of tumor and normal nerve tissue becomes possible using a low dose of SF (0.5-1 mg/kg). No side effects occurred. Secure microsurgical preparation is feasible during application of the YELLOW 560 nm filter.