What you see and what you don't - Utility and pitfalls during fluorescence guided resections of gliomas using 5-aminolevulinic acid.

Background: Fluorescence guided resections have been increasingly used for malignant gliomas. Despite the high reliability of the technique, there remain some practical limitations.Methods: We retrospectively reviewed our experience with 50 consecutive cases of 5-aminolevulinic acid (ALA)-guided resections. Clinico-radiological features and intraoperative variables (pattern and type of fluorescence) were recorded. In a subset (12 cases), we performed annotated biopsies to calculate the diagnostic accuracy of the technique. We recorded and analysed the patterns of excision and residual fluorescence and correlated this with postoperative magnetic resonance imaging (MRI).Results: Majority of the tumours (92%) were resectable and predominantly enhancing. Though strong fluorescence was seen in most of them, there were 2 cases with a non-enhancing tumor which showed fluorescence. Visualized strong fluorescence had a very high predictive value (100%) for detecting the pathological tissue. However, it was not always possible to resect all the fluorescing tissue. Proximity to critical neuro-vascular structures was the commonest reason for failure to achieve a gross total excision (16 cases). Additionally, there were some cases (5 of 8) where the non-fluorescing residue was resected intraoperatively with the help of ultrasound. Despite the presence of residual fluorescence, overall radiological gross total resection was achieved in 66% cases.Conclusions: ALA guided resections are very useful in malignant gliomas, even if these lesions do not enhance signi cantly. Although ALA reliably depicts the tumour intraoperatively, it may not be possible to resect all this tissue completely. Additionally, non-fluorescing tumor may be completely missed out and may require additional imaging tools. Working within the limitations of the technique and using complementary modalities (ultrasound or brain mapping) may be ideal for achieving a radical resection of malignant gliomas. [ABSTRACT FROM AUTHOR]

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