There are a few diagnoses that must be considered when presented with a mass lesion at the base of the skull in the clival/petrous region. The classic differential diagnosis of the more common entities in this location includes:
» chordoma
» chondrosarcoma
» metastatic disease (predominantly due to direct spread from nasopharynx)
» multiple myeloma (plasmacytoma when solitary lesion)
» cholesteatoma


» Chordoma - is more likely to be midline centered in clivus (low T1, high T2, enhancing)
» Chondrosarcoma - is more likely to be off midline centered in the petro-occipital fissure that harbors chondroid cells along its cartilagenous surface. (low T1, high T2, may have hypointense foci representing chondroid matrix, enhancing)
» Metastatic tumor - destructive lesion, either direct extension from a nasopharynx or known remote primary tumor. (MRI variable depending on a primary, enhancing)
» Plasmacytoma - clival or peri-clival, over 50% of patient have additional lesions and carry diagnosis of multiple myeloma (low T1 and T2, enhancing)
» Cholesteatoma - usually smooth petrous apex lesion without enhancement.