Fig 1.

De novo development of a lesion with the appearance of a cavernous malformation adjacent to an existing developmental venous anomaly.

A and B, T2-weighted axial MR imaging sections of the cerebellum obtained approximately 3 years before current presentation demonstrates a developmental venous anomaly within the right cerebellar hemisphere.

C and D, Postgadolinium-enhanced axial T1 images obtained at same levels of A and B demonstrate the characteristic enhancement and caput medusae distribution of the developmental venous anomaly, which drains anteriorly via an enlarged medullary vein.

E and F, MR images obtained following patient’s presentation with acute onset of dizziness, headache, and left sided paresthesias demonstrate development of a complex lobulated cystic hemosiderin-containing lesion measuring approximately 1.5 cm × 1.2 cm in size in the lower right cerebellum. The lesion is located within parenchyma that is in the drainage pattern of the developmental venous anomaly.

G and H, Follow-up MR images obtained 2 years later demonstrate a decrease in the size of the hemosiderin-containing abnormality, which now measures approximately 1 cm in diameter. The lesion has also become less complex in appearance.