A lobulated tumour measuring 2.8 x 1.6 x 2.7 cm centred at the prepontine cistern is brightly T2 hyperintense with internal small foci of T2 hypointensity, mild to moderately T2 FLAIR hyperintense and predominantly T1 hypointense. The bulk of the tumour moderately enhances. Several tiny foci of internal calcification are seen on CT, with erosion of the clivus, attenuation of part of the dorsum sellae, as well as breach of the medial posterior wall of the left carotid canal with small bony fragments.
The posterior aspect of the tumour abuts the basilar artery, but without evidence of significant compression, with preserved basilar flow void and enhancement. A tongue of tumour on the right protrudes to abut the right side of the basilar artery and mildly indents the right anterior pons with normal pontine signal preserved (thumb sign). Inferiorly, it drapes along the posterior surface of the clivus to 1 cm from the clival tip. Superiorly, it reaches at the level of the posterior clinoid process. Anteriorly, a component on the left extends medial to the medial wall of Meckel's cave, displacing it laterally, erode the posteromedial wall of the carotid canal, with tumour abutting the carotid artery from the medial left carotid canal and as it ascends in the posterior left cavernous sinus. The calibre of the left carotid artery at the medial most aspect of the left carotid canal appears narrowed.
Moderately large left temporal arachnoid cyst extends superiorly to splay the opercular left frontal and temporal lobes.