Photodynamic Success Against Skull Base Brain Tumors
About one in every five primary brain tumors are classified as meningiomas, and approximately 25% of these are located in the base of the skull. These tumors actually form within the bones that form the bottom of the skull and the bony ridge in the back of the eyes. Skull-base tumors are invasive and intimately associated with cranial nerves, vessels, and the brainstem. The aim of surgical treatment for such tumors is maximum possible removal of the tumor (resection) with minimal damage to the brain and nervous system.
For surgeons, skull-base meningiomas pose a tremendous challenge and are difficult to remove because of their particular location and extensive spread. These tumors are often believed to have a higher rate of recurrence and worse prognosis compared with other types of meningiomas.
Neuroscientists at the Heinrich-Heine-Universität in Düsseldorf, Germany, recently presented a case of a recurrent skull base meningioma treated with an innovative surgical strategy. The surgical team used the photosensitizer precursor, 5-ALA, which causes tumor tissue to fluoresce or glow upon exposure to light. Fluorescence-guided surgery has already been extensively studied with regard to various brain tumors.
In this case, the patient underwent surgery guided by both 5-ALA fluorescence and F-fluoroethyltyrosine (FET)-PET-imaging. Both the microscope and the endoscope were equipped for 5-ALA fluorescence-guided surgery. In addition, the researchers merged the FET-PET imaging computed tomography (CT scans) and magnetic resonance imaging (MRI) data in order to help navigate through the brain tissues during the entire operation.
The researchers concluded that 5-ALA fluorescence-guided resection and FET-PET were helpful for the surgical treatment of this complex-shaped, recurrent skull base meningioma. The 5-ALA fluorescence was effective as a way to dissect the interface between tumor and brain itself, and it helped to reveal the tumor margins within the nasal cavity. Meanwhile, the FET-PET imaging improved the assessment of spinal and bony infiltration.
“We hypothesize that these imaging technologies may reduce recurrence rates through better visualization of tumor tissue that might be left unintentionally,” the German investigators wrote. “This has to be verified in larger, prospective [clinical] trials.” They published this case report in a recent issue of the Journal of Neurological Surgery. Part B, Skull Base.
Meanwhile, a research team from Brazil reports that other types of meningiomas may be effectively revealed with a fluorescing compound called sodium fluorescein, and studies are ongoing to assess the usefulness of this compound for fluorescence-guided surgery, as reported in the 14 January 2014 issue of Surgical Neurology International.
For more information about the promise of photomedicine, please see our book, The Medicine of Light and our PhotoMed Discoveries ebooks.
Cornelius JF1, Slotty PJ1, Stoffels G2, Galldiks N2, Langen KJ2, Steiger HJ1. 5-Aminolevulinic Acid and (18)F-FET-PET as Metabolic Imaging Tools for Surgery of a Recurrent Skull Base Meningioma. J Neurol Surg B Skull Base. 2013 Aug;74(4):211-6.
da Silva CE, da Silva VD, da Silva JL. Convexity meningiomas enhanced by sodium fluorescein. Surg Neurol Int. 2014 Jan 14;5:3. eCollection 2014.
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