To The Editor: We have read with interest the article by Cage et al.2 (Cage TA, Pekmezci M, Prados M, et al: Subependymal spread of recurrent glioblastoma detected with the intraoperative use of 5-aminolevulinic acid. Case report. J Neurosurg 118:1220–1223, June 2013).
We agree with the assertions that “magnetic resonance imaging may not completely detect the presence of diffuse tumor, . . . [and the] intraoperative use of fluorescence-assisted visualization with 5-ALA may be helpful in highlighting and detecting infiltrative tumor.”
We have recently published data supporting that role of 5-aminolevulinic acid (5-ALA).1 However, their statement that 5-ALA “confirmed that there was subependymal and ependymal spread” is unsupported, as they do not provide separate biopsies of those infiltrated areas. Optic radiation spreading would provide an alternative explanation for the connection of the recurrent tumor to the original site and would also explain the clinical symptoms.
In a number of papers, intense fluorescence from 5-ALA has been shown to be highly predictive of tumor histology;3–6 however, faint fluorescence in the ependymal wall might be an exception. We reviewed 45 patients with tumors contacting the ventricular wall and found ependymal fluorescence in 28. Selective biopsies were performed when taking the sample was considered safe, and the results were negative in 3 of 8 cases.7 Furthermore, clinical evolution of the group of patients with ependymal fluorescence was similar to the group without it, suggesting that there was not true ependymal spreading.
CITATION J Neurosurg. 2013 Aug;119(2):530-1. doi: 10.3171/2013.3.JNS13498. Epub 2013 Jun 7.
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