RESUMO
The authors report a very unusual case of ruptured aneurysm by direct vessel invasion of anaplastic oligodendroglioma (WHO grade III) confirmed by histopathological examinations. As local invasion is the hallmark of malignant gliomas, malignant glial tumors invade neighboring structure and often cause microscopic endothelial proliferation, telangiectasias in small arteriols, but direct arterial invasion by glioma is very rare. Possible mechanisms of intracranial aneurysm development by glioma are thought to be related to the close proximity to the tumor, perivascular basement membrane breakage due to high tumor pressure and increased regional blood flow through the feeding artery of tumor. The aneurysm and tumor were treated in a single operation simultaneously.