Angiographic diagnosis of fourth ventricle tumors.

Twelve primary fourth ventricle tumors and 22 medulloblastomas occupying mainly the fourth ventricle were analyzed, with emphasis on the differential diagnosis, vascularity, and some unusual findings. Though both types of tumor often have identical manifestations, the correct diagnosis can be made in most cases by careful evaluation of the posterior inferior cerebellar artery, particularly the choroidal and nodular branches. Unusual findings in primary fourth ventricle tumors mimicking tumors of the pons and medulla oblongata are described, and possible explanations for these findings are discussed. The results of this study underscore the importance of angiotomography in the diagnosis of tumors of the fourth ventricle.