Centered in the superior midbrain is a rounded lesion with peripheral signal drop-out (best seen on gradient echo sequence - GRE) consistent with hemosiderin. Centrally the lesion is markedly heterogeneous in signal with regions of high signal on both T1 and T2 weighted images. There is no peripheral oedema and no evidence of hydrocephalus.
Features are characteristic of a midbrain cavernous malformation.