Subependymal spread of recurrent glioblastoma detected with the intraoperative use of 5-aminolevulinic acid Case report

Recurrent glioblastoma (GBM) can occur locally or at distant sites within the brain. Though MRI is the standard imaging modality for primary and recurrent GBM, the full extent of diffuse lesions may not be appreciated on MRI alone. Glioblastomas with ependymal and/or subependymal spread are examples of diffuse infiltrative tumors that are incompletely seen on MRI. Some other adjuvant visualization technique such as intraoperative fluorescence-assisted 5-aminolevulinic acid (5-ALA) could be used to assist the surgeon in localizing the infiltrating tumor. The authors report on a 56-year-old man who presented 7 years after initial resection of an occipital lobe GBM with imaging consistent with distant discrete foci of tumor recurrence. Because these foci were distant from the original resection cavity, there was concern for diffuse, infiltrative tumor elsewhere throughout the brain versus a distant multicentric recurrence. Therefore, the patient was given 5-ALA prior to surgery to aid in tumor detection intraoperatively. Using fluorescent visualization of the resection cavity, it was confirmed that there was subependymal and ependymal spread of the recurrent tumor along the lateral ventricle connecting the recurrence to the previous tumor site. Magnetic resonance imaging may not completely detect the presence of diffuse tumor infiltrating the ependymal or subependymal spaces. Therefore, adjunct intraoperative use of fluorescence-assisted visualization with 5-ALA may be helpful in highlighting and detecting infiltrative tumor to accurately detect tumor burden and distinguish it from a separate multicentric recurrence.