The use of fluorescein fluorescence-guided stereotactic needle biopsy has been shown to improve diagnostic accuracy and to expedite operative procedure in the stereotactic needle biopsy of high-grade gliomas.
The first use of fluorescence for brain tumour surgery was in 1948 by G.E. Moore 1) 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 3) 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 perfused brain tissue. Such time-resolved in- formation on the specificity of fluorescein are not available.
Overall, Schwake et al observed no clear value of fluorescein in a small study, which they closed prematurely. Clearly, further work elucidating optimal timing and dosing of fluorescein is warranted. 5)
Also in skull base tumors 12).
“Fluorescein sodium”, the sodium salt of fluorescein, is used extensively as a diagnostic tool in the field of ophthalmology and optometry, where topical fluorescein is used in the diagnosis of corneal abrasions, corneal ulcers and herpetic corneal infections. It is also used in rigid gas permeable contact lens fitting to evaluate the tear layer under the lens. It is available as sterile single-use sachets containing lint-free paper applicators soaked in fluorescein sodium.
Intravenous or oral fluorescein is used in fluorescein angiography in research and to diagnose and categorize vascular disorders including retinal disease macular degeneration, diabetic retinopathy, inflammatory intraocular conditions, and intraocular tumors. It is also being used increasingly during surgery for brain tumors.
Diluted fluorescein dye has been used to localise multiple muscular ventricular septal defects during open heart surgery and confirm the presence of any residual defects.
Intravenous fluorescein sodium has been used during resection of high grade gliomas to help the surgeon visualize tumor margins. Several studies have reported improved rates of gross total resection (GTR) using high doses of fluorescein sodium under white light. The introduction of a fluorescein-specific camera that allows for high-quality intraoperative imaging and use of very low dose fluorescein has drawn new attention to this fluorophore.
Fluorescein sodium does not appear to selectively accumulate in astrocytoma cells but in extracellular tumor cell rich locations, suggesting that fluorescein is a marker for areas of compromised blood brain barrier within high grade astrocytoma. Fluorescein fluorescence appears to correlate intraoperatively with the areas of MR enhancement, thus representing a practical tool to help the surgeon achieve GTR of the enhancing tumor regions 13).
Magnetic resonance diffusion tensor imaging (MR-DTI) and fluorescein sodium dyeing guiding for surgery of glioma located in brain motor functional areas can increase the gross total resection rate, decrease the paralysis rate caused by surgery, and improve patient quality of life compared with traditional glioma surgery 14).
Intrathecal fluorescein (ITF) is extremely specific and very sensitive for detecting intraoperative CSF leaks. Although false negatives can occur, these patients do not appear to be at risk for postoperative CSF leak. The use of ITF may help surgeons prevent postoperative CSF leaks by intraoperatively detecting and confirming a watertight repair 15).