Brain stem cavernous angioma and unusual basla venous network

This 18 year old female presented with headache and right hemihypaesthesia involving the face.
MRI demonstrated a cavernous angioma in the upper part of the mesencephalon on the left side. MRA, performed at the same time, revealed a very unusual pattern of the basal venous system.
Unfortunately, the patient had a massive bleed from the cavernous angioma a few days later resulting in acute hydrocephalus and coma.

(Brain stem cavernous angioma, 1.5T)
Fig.1 Sagittal Gadolinium-enhanced T1-weighted spin-echo images. Rounded, slightly inhomogeneous lesion in the mesencephalon with faintly enhancing rim.
Fig.2 Transverse proton-density and T2-weighted fast spin-echo images. The lesion situated in the left cerebral peduncle has a hyperintense center surrounded by a very faint hypointense rim on these sequences. There is very little peripheral edema.
Fig.3 Transverse non-enhanced (above) and Gadolinium-enhanced (below) T1-weighted spin-echo images. Same observations as on Fig.1.
Fig.4 Transverse T2-weighted gradient-echo images. The hypointense rim (hemosiderin deposits) of the lesion becomes more prominent and the diagnosis of cavernous angioma is suggested.
Fig.5 Transverse MIP reconstructions from non-enhanced (above) and Gadolinium-enhanced 3D TOF MRA acquisition data sets. The non-enhanced image is unremarkable as no venous structure is seen due to intravolume spin saturation. The contrast-enhanced image reveals an unusual pattern of the basal venous network.
Fig.6 Targeted transverse MIP reconstructions from the Gadolinium-enhanced 3D TOF MRA acquisition data set. These images clearly shows a well developed right basal vein of Rosenthal receiving an unusual perimesencephalic vein draining the contralateral uncal area. On the left side, the basal vein is absent. Instead a very prominent retropulvinar vein is seen in proximity to the previously identified cavernous angioma.
Fig.7 Transverse source images from a Gadolinium-enhanced 3D TOF MRA sequence using high resolution matrix, MOTSA and magnetization transfer, providing parenchymal landmarks for the most prominent elements of the unusual basal venous network.
N.B. This unusual network is certainly not a true DVA in the classical sense of the term. However it was still felt to represent an extreme variant of the basal venous drainage and to have a possible correlation with the cavernous angioma.

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