Preoperative embolization of highly vascular brain tumors: clinical and histopathological findings

This report concerns the clinical and histopathologic findings in five patients with meningioma and two with hemangioblastoma who underwent embolization with polyvinyl alcohol (PVA) particles before surgery. Angiography revealed loss of tumor stain from the main feeders in all seven patients, with markedly decreased contrast enhancement of computed tomography (CT) and magnetic resonance imaging (MRI) in six of them. Tumor excision was readily accomplished in all instances, with minimal bleeding from the tumor. In the patient operated 1 day after embolization there were almost no necrotic lesions, even though hemorrhage, presumably due to the surgical procedure was noted. Necrotic lesions and island-like residual tumor cells around the vessels were seen in the patient operated two days after embolization. Extended necrotic lesions were noted among patients who underwent surgery at day 4 and thereafter. Revasculization was not found, even in the patient operated one week after embolization. Massive bleeding (due presumably to the surgical procedure, suggesting recanalization) was noted in the tissue of a hemangioblastoma patient who underwent surgery 13 days after embolization, even though tumor excision was easy. In the patient subjected to the surgical procedure 694 days following embolization, the CT and MRI performed 2 months later, revealed contrast enhancement similar to that seen before the operation. Moreover, angiography, done after 5 months, demonstrated tumor stain as had been noted before embolization. The histopathologic examination of this case reveal the presence of extended necrotic lesions, a large number of macrophages that contained PVA particles, and destruction of the walls of the onceoccluded vessels. In addition, there were many blood-filled vessels that had achieved recanalization. These findings suggest that it is desirable to operate within 7 days after embolization, since recanalization occurs during this period, even though PVA particles remain unabsorbed for a long time.