Multiple myeloma presenting with unilateral abducens and trigeminal nerve palsies

Petrous apex masses can manifest with neurologic symptoms due to their involvement of various structures, including cranial nerves (CN) V and VI. The differential diagnosis of petrous masses is broad and includes a variety of both non-neoplastic and neoplastic lesions. We report a rare case of multiple myeloma confined to the right petrous apex, presenting with ipsilateral abducens and trigeminal nerve palsies. A 63-year-old woman presented with a 6-8 week history of facial numbness and a 2 week history of diplopia, with examination showing right-sided facial hypoesthesia in the CN V1-V3 region and right-sided lateral rectus palsy. MRI of the brain showed a solitary 2.0 cm lesion confined to the right petrous apex involving the right cavernous internal carotid artery and Meckel's cave. A transnasal biopsy showed a proliferation of plasmacytoid cells, which showed diffuse immunoreactivity with antibodies to CD138 and kappa, consistent with a plasma cell dyscrasia. A bone scan subsequently revealed multiple lytic bone lesions involving the skull, left humerus, bilateral femurs and possibly the L4 vertebral body. Bone marrow biopsy and serum laboratory results confirmed the diagnosis of kappa-type multiple myeloma. Although rare, multiple myeloma may initially present with petrous involvement and associated cranial nerve deficits.