Simultaneous fluorescein sodium and 5-ALA in fluorescence-guided glioma surgery

Dear Editor, Five-aminolevulinic acid (5-ALA)-derived fluorescence is approved for fluorescence-guided resections of malignant gliomas, relying on selective synthesis and accumulation of protoporphyrin IX (PPIX) within malignant glioma cells [5].However, the first use of fluorescence for brain tumour surgery was in 1948 by G.E. Moore [3] using fluorescein sodium, a strongly fluorescing and non-toxic (apart from rare anaphylaxis [2]) compound.In malignant brain tumours with their inherent blood-brain barrier breakdown, fluorescein is extravasated and might serve to mark tumours.Today, fluorescein sodium is again under scrutiny [1, 4] using a novel filter system by Zeiss (YELLOW 560) for the microscope.This filter visualises fluorescein and allows good background discrimination.Furthermore, fluorescein can be injected any time and is low in cost.Nevertheless, its use in brain tumour surgery is off-label and thus restricted to clinical studies.Little is known about the best timing of i.v.fluorescein application before resection.Injecting fluorescein too early might result in unspecific propagation with oedema, whereas acute injections might be useful for detecting abnormally perfused tumour tissue.Levels in the blood will be high, especially with acute injections, leading to fluorescence of all per-*