Here were the findings from the initial MRI, for anyone who is curious:
There is a high T2, homogeneously densely enhancing mass expanding the petrous apex and left side of the clivus. Dimensions are 29 x 34 mm, extending cranial caudal for 33 mm. There is extension into the left prepontine cistern with mass effect on the pons. This would be in a position to involve the left cranial nerve VI. The mass also involves the left middle fossa with some mass effect on the left temporal tip. The mass is extradural with no signal abnormality in the adjacent brain parenchyma. The left internal carotid artery is displaced by the mass, but does not appear narrowed and contains a normal flow void. There is minimal encroachment on the cavernous sinus. The orbital apex is unremarkable. The mass is clearly distinct from the pituitary gland. The orbits and extraocular muscles are unremarkable. There is no acute infarct identified on diffusion-weighted imaging. There is no hemorrhage or extra-axial collection. The ventricular and sulcal pattern is otherwise unremarkable without midline shift. Impression: Skull base/clivus mass. Differential includes chordoma, chondrosarcoma, and plasmacytoma/metastasis.