Visualizing protoporphyrin IX formation in the dura tail of meningiomas by mass spectrometry imaging

Area of Science:

• Neurosurgery
• Oncology
• Molecular Imaging

Background:

• 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery (FGS) is increasingly used for meningiomas.
• Tumor tissue in the dura tail may not fluoresce under standard microscopy despite histopathological confirmation.
• Understanding 5-ALA metabolism in the dura tail is crucial for FGS in meningiomas.

Purpose of the Study:

• To investigate the presence and distribution of protoporphyrin IX (PpIX) in sphenoid ridge meningioma, specifically in the dura tail.
• To correlate fluorescence observed during surgery with molecular imaging findings.

Main Methods:

• Spatially resolved molecular imaging analysis using matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS).
• Analysis of cryosections from sphenoid ridge meningioma, including the dura tail.
• Comparison of MALDI-MS/MS findings with standard operating microscope visualization.

Main Results:

• Despite no visible fluorescence at the dura tail under the operating microscope, histopathology confirmed meningioma tissue.
• MALDI-MS/MS detected protoporphyrin IX (PpIX) formation in the non-fluorescing dura tail.
• PpIX was selectively accumulated in tumor tissue, including the dura tail, but not in tumor-free dura mater.

Conclusions:

• The absence of fluorescence in the dura tail during 5-ALA FGS is not due to a lack of PpIX formation.
• MALDI-MS/MS imaging reveals PpIX accumulation in the dura tail, suggesting potential for FGS in this region.
• Further evaluation of FGS indications in meningiomas should consider these molecular imaging findings.