Cerebral venous malformation-arteriovenous malformation transition forms.

Three cases of cerebral venous malformation (CVM) are presented to demonstrate the triad that characterizes CVM: abnormal surface venous drainage, a "star-cluster" system of deep collecting veins, and a deep draining vein. Four other cases are introduced that illustrate this triad and show an additional feature, namely arterial fistulization; these cases represent arteriovenous malformations (AVMs). A final case demonstrates a CVM within an AVM. Both of these structures have a common draining vein and an identical venous core. On the basis of the cases described and of others less suitable for illustration, it is postulated that an AVM is a fistulized CVM and that both relate to a failure in the development of the cortical venous mantle. This proposition is based on the authors' observations and their assessment of the "best possible fit."