Extra-axial growth of fourth ventricle tumors - angiographic changes.

Tumors of the fourth ventricle, particularly ependymomas, may grow out of the ventricular cavity into the cerebellopontine angle cistern and the subarachnoid cisterns. The angiographic changes will then suggest both the intra- and extraventricular location of the tumors. The ependymoma is the most prone of the fourth ventricle tumors to demonstrate this pattern of growth.