Weird case: 50-something with longstanding history of diplopia 


Lytic skull base lesion seems centered around petrous bone/foramen lacerum. Smooth, rounded, sclerotic (not obvious in this but clearer in other cuts) suggestive of benign, slow growing process like a vascular malformation rather than an invasive, destructive cancer like osteosarcoma (where you'd see spiculated bony edges)


Mottled appearance on thin-cut T1 GAD

Very mottled appearance on thin-cut T1 GAD 

The danger of volume averaging -- on the thicker-cut T1 GAD slices, mass appears much more homogenously enhancing.

One tiny dot of flow void/susceptibility on GRE, but otherwise nothing. 

Differential Diagnosis: 

- Trigeminal Schwannoma - although one would expect the tumor to follow the course of the trigeminal nerve, and it doesn't

- Meningioma - doesn't display bony hyperostosis, however in the literature only 25-50% of skull base meningiomas demonstrate hyperostosis, This paper (http://www.ncbi.nlm.nih.gov/pubmed/10201298) found a 51% rate and histologically showed that the vast, vast majority of cases of hyperostosis was secondary to tumor invasion into the bone. Although there were patients with tumor invasion into bone that did not display hyperostosis. 

- Hemangiopericytoma: possible given clivus bone bmarrow signal heterogeneity (which may be reactive). Per this paper (http://www.ncbi.nlm.nih.gov/pubmed/21529166), hemangiopericytoma can look very similar to meningiomas on imaging. Ways to differentiate: hemangiopericytomas frequently have serpentine flow voids, lobulated edges, mottled enhancement, erode into neighboring bone, are not surrounded by a ton of edema, and almost never have calcifications. Meningiomas typically have smooth edges, homogenous enhancements, ~20-25% are calcified. Hemangiopericytomas are also much more rare. On angio, hemangiopericytomas are usually supplied by ICA (vs ECA for meningiomas) have corkscrew vessels arising from main feeder artery, "dense, fluffy, long-lasting" tumor stain rather than sunburst blush of meningoma. 

- Mets, although no permeative bone destruction, and no known primary

- Paraganglioma: no susceptibility/flow voids

- Venous malformation -- typically these have flow voids/susceptibility, and they look different-- on T2 or T1 GAD, they look almost like halfway between an AVM and a tumor -- nests of these dilated, wormy appearing things; they are congenital and have no respect for traditional anatomic boundaries or tissue planes - can be in bone/soft tissue/etc. This tumor is more smoothly enhancing and homogenous 

- Vascular tumor - not the same thing as a vascular malformation.