Presentation
Diplopia and headache.
Patient Data
An expansile bone lesion is noted at the right petrous apex measuring 3 x 1.7 x 3.5 cm in AP, SS and CC dimensions with mild heterogeneous texture with intact outline covered with intact thin cortical rim.
It is extending all through the right side of the clivus involving the region of right Dorello canal with a narrow transition zone and sharp lobulated contours. It expresses low signal intensity on T1, high signal intensity on T2 and FLAIR, heterogeneous postcontrast enhancement, no diffusion restriction and no haemorrhagic changes with partial preservation of internal bone septae but rarefaction.
It is encroaching upon the right CPA cistern and right side of prepontine cistern. It exerts narrowing of the right vestibular aqueduct.
Thinning and elongation of right lateral rectus muscle with esotropia of right eye, suggestive of right abducens nerve palsy.
Case Discussion
Features of expansile right petrous apex lesion. Internal enhancement raises the possibility of intraosseous tumours. This case is known for petrous apex chondrosarcoma (pathologically proved - pathology report not available) and was referred for MRI assessment before Gamma Knife surgery.
The lesion is replacing the right Dorello's canal with the right VI nerve seen entering it. The right VI nerve is also markedly displaced to the right side and stretched by the dolicoectatic basilar artery. Together explain the presence of diplopia.
Petrous apex chondrosarcoma is a rare lesion of the petrous apex. The presence of enhancement is a clue for suspicion of a bone tumour.
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