Developmental venous anomaly with radiation-induced arteriovenous malformation.

Developmental venous anomaly (DVA) is considered a congenital vascular anatomic variation with normal draining function. Limited cases of DVA with arteriovenous malformation (AVM) in the territory of DVA have been reported, and the etiology of de novo AVM formation remains unknown and speculative. In this case, it is continuously observed that the inappropriate radiosurgery involving the DVA draining veins led to the disruption of DVA radicles and the secondary formation of de novo AVM and hemodynamic aneurysm. This sequential process exhibited in the present case verified that outflow disturbance underlay the potential etiology of AVM formation drained by adjoining DVA. Meanwhile, it also manifested the importance of preserving the integrity of the collecting veins when treating the DVA by any means.