[Efficiency of Embosphere in the Pre-Operative Embolization of Meningioma:Clinical Experience]

Embosphere^® was approved in Japan for embolizing intracranial arteries for the reduction of intraoperative bleeding in January 2014. Until August 2015, we performed embolization for four meningiomas using Embosphere^®. We performed an initial evaluation of all the cases, including evaluation of the clinical courses, change in the maximum tumor diameters and volumes, alteration in the appearance on magnetic resonance imaging(MRI), amount of intraoperative bleeding, complications, and histopathological findings. After embolization, the maximum tumor diameters and volumes slightly decreased on MRI, whereas the signal change on diffusion-weighted imaging(DWI)or fluid-attenuated inversion recovery(FLAIR)varied in each case. One case demonstrated a partial signal change on DWI one day after the initial procedure, and another case demonstrated a decrease in perifocal edema on FLAIR. Among our patients, least bleeding was recorded at 6 days after the embolization. Histopathological analysis revealed coagulative necrotic lesions in two cases. The von Kossa stain was used to distinguish Embosphere^® from the psammoma body. One case involved a thromboembolic complication of the retinocentral artery caused by an Embosphere^® of 100-300 μm. Our early-stage experience suggests that an Embosphere^® of 300-500 μm should be used for safe embolization before resection to avoid thromboembolic complications because an Embosphere^® of 100-300 μm can pass through the dangerous anastomosis. Our present strategy was to resect the tumor approximately seven days after the embolization using Embosphere^®. However, further studies and discussion on the size of Embosphere^®, and the interval between pre-operative embolization and surgical removal are needed.