Specific Imaging Findings

Developmental venous anomalies (DVAs, venous angiomas, venous malformations) consist of dilated medullary veins draining centripetally and radially into a transcerebral collector that ultimately converges into the deep or superficial venous system in an area in which there is an absence of normal draining veins. The caput medusae (head of the Medusa) represents the typical morphological appearance of DVAs: contrast enhancement of the network of feeding veins converging into the single draining vein is caused by the slow flow on both CT and MR imaging. Size of DVAs is quite variable, and large DVAs draining an entire hemisphere may be occasionally observed. The draining vein of large DVAs can demonstrate flow-void (high-velocity signal loss best seen on T2WI), whereas medullary veins and smaller collecting veins are frequently seen as T2 hyperintensities, or they may remain imperceptible on non-contrasted MR images. If the vessel is obliquely oriented, a “yin–yang” symbol appearance may occur because of the characteristic spatial misregistration artifacts associated with venous flow. DWI/ADC findings are usually unremarkable. Brain parenchyma adjacent to DVAs is most commonly normal on standard images however, a minority of DVAs are associated with T2 hyperintensity in the drainage territory, usually in a periventricular location. DVAs are usually not visible on unenhanced CT.

Pertinent Clinical Information

DVAs are most commonly incidentally found on MR imaging and are estimated to occur in around 3% of individuals. There is an association with sporadic cavernous malformations but not with familial cavernomas. De-novo cavernomas have been described to occur adjacent to pre-existing DVAs. DVA is generally considered a benign finding. Notwithstanding, a variety of symptoms including headache, non-communicating hydrocephalus, tinnitus, and cranial nerve dysfunction have been described in association with DVAs. As with other venous structures, thrombosis may occur in DVAs. Hemorrhage in association with DVAs has been described, especially in the cerebellum.