Figure 18.

Cholesterol granuloma. (A) Axial fat-suppressed T2W and (B) noncontrast T1W images show a lobulated, expansile lesion in the right petrous apex with intrinsic high signal intensity on T1 and mixed signal intensity with smooth hypointense margins on T2. The lesion is in close proximity with the petrous ICA (white arrow). (C) Axial CISS image shows extension of the lesion into the right cerebellopontine angle with mild mass effect on the pons and abutment of the basilar artery (blue arrow). The lesion effaces right Dorello’s canal, where there is mass effect with effacement of the cisternal segment of the right sixth cranial nerve (red arrow). (D) Axial fat-saturated postcontrast T1-weighted image demonstrates no significant enhancement of the lesion, although this is difficult to evaluate due to intrinsic T1 hyperintensity.