5-ALA Enhanced Fluorescence-Guided Microscopic to Endoscopic Resection of Deep Frontal Subcortical Glioblastoma Multiforme.

Glioblastoma multiforme remains the most common adult primary brain tumor with a life expectancy of 15-18 months following best treatment strategies. Current paradigms incorporate maximal safe resection, chemotherapy, and radiation. Multiple variables correlate with increased survival; perhaps most notably are stepwise survival advantages following 78% and 98% extent of resection thresholds. 5-Aminolevulinic acid has become a vital tool in the intraoperative identification and differentiation of high-grade glioma as it provides a fluorescent effect capable of distinguishing tumor from normal brain tissue when observed under blue light, which to date has been used primarily via a microscopic light source. However, this effect is attenuated with increasing distance between the blue light source and the tumor, as in the case of deep seated resection cavities. We aimed to overcome this obstacle by using a blue light endoscope as the primary visualization platform, thereby advancing the light source directly into the resection cavity. We present the case of a 69-year-old man with a deep left frontal subcortical lesion proven to be glioblastoma multiforme on prior biopsy. He consented to undergo an interhemispheric "M2E" (microscopic-to-endoscopic) approach with subcortical motor mapping. Tumor fluorescence under blue light visualization was not appreciated by the operating microscope but was easily observed with the blue light endoscope. Tumor resection proceeded under direct blue light endoscopy with intermittent subcortical motor mapping until a threshold of 4 mA was reached. The patient had transient right arm and leg weakness. Postoperative magnetic resonance imaging confirmed >98% resection (Video 1).