Visualization of 5-Aminolevulinic Acid Flourescence in Low Grade Gliomas

Laura A. Snyder, MD1, Norissa Honea1, Stephen Coons, MD1, Stephen Chang, MD1, Porter Randall, MD1, Kris Smith, MD1, Robert Spetzler, MD1, Nader Sanai, MD1

1Phoenix, AZ United States

Keywords: glioma, Imaging, astrocytoma, brain tumor, resection

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     Greater extent of resection (EOR) for low-grade glioma (LGG) patients corresponds with improved clinical outcome, yet remains a challenge to the neurosurgical oncologist. Although 5-aminolevulinic acid (5-ALA)-induced tumor fluorescence improves glioma extent of resection, only glioblastomas routinely fluoresce with 5-ALA. Intraoperative confocal microscopy adapts confocal technology to a handheld probe, providing real-time cellular fluorescent imaging at 1000-fold magnification.
     We report the first combined approach using intraoperative confocal microscopy to visualize 5-ALA fluorescence in LGG during microsurgical resection.
     Following 5-ALA administration, 10 newly-diagnosed LGG patients underwent microsurgical resection.
     Confocal microscopy was conducted at initial tumor encounter, midpoint of tumor resection, and presumed brain-tumor interface. Correlative histopathological analysis of these sites was performed. Routine pre- and postoperative clinical data, including neurological deficits and volumetric EOR, were quantified.
     Ten consecutive patients with WHO grades I and II gliomas underwent microsurgical resection using 5-ALA and intraoperative confocal microscopy. Macroscopic tumor fluorescence was not evident in any patient. However, in all cases, intraoperative confocal microscopy identified tumor fluorescence at a cellular level, a finding that corresponded to tumor infiltration on matched histological analyses. In 3 patients (30%), the presence of infiltrating tumors at the margins did not correspond with neuronavigational MR imaging and led to additional tumor resection.
     This is a retrospective study.
     Intraoperative confocal microscopy can routinely visualize cellular 5-ALA-induced tumor fluorescence within LGG and at the brain-tumor interface.
     This combination of technologies enables a quick optical biopsy at the margins of resection, enabling verification of neuronavigational imaging and a real-time, in vivo assessment of microscopic residual.


Project Roles:

L. Snyder (), N. Honea (), S. Coons (), S. Chang (), P. Randall (), K. Smith (), R. Spetzler (), N. Sanai ()