A well defined lobulated mass measuring 3.5 x 3.5 x 5.8 cm centred at the right clivus, crossing the midline by 4 mm, is heterogeneous, but predominantly T1W hypointense, brightly T2W hyperintense, with loculated/bubbly internal enhancement. It has a well-defined thin sclerotic margin medially, and an ill-defined permeative margin laterally with mass effect upon the right anterior mesiotemporal lobe. There is breach of bony cortex posteriorly with a 14 x 6 mm soft tissue projection that protrudes into the prepontine cistern, beneath dura, but lying in close proximity to the basilar artery. There is also destruction of the right carotid canal with small foci of ossific debris/coarse calcification that are T1W hyperintense. The right cavernous carotid artery is displaced, but its course lies predominantly inferomedial. Normal cavernous carotid flow void is preserved although mild narrowing is present. The right cavernous sinus and Meckel's cave are obliterated. The lateral wall of the right sphenoid sinus is remodelled, and intact, with the sinus well aerated. Part of the superolateral wall of the right foramen rotundum is breached. Right foramen ovale is slightly widened. The right hypoglossal canal is breached superiorly. Tumour lies close to the right optic canal, but the optic canal is not compromised. Inferiorly, a tongue of tissue has protruded into the right longus capitis muscles, but is 7 mm from the right nasopharyngeal mucosa. Right cochlear and vestibular apparati, middle ear and mastoid uninvolved. Right jugular foramen also appears uninvolved. Minor chronic small vessel ischaemic change. No diffusion restriction. Thickened left maxillary sinus walls with mild mucosal thickening in keeping with chronic sinusitis.
Conclusion: Right central skull base tumour most likely to represent chondrosarcoma or (eccentric) chordoma with extent as described.