Multiple Myeloma Manifesting as a Fluctuating Sixth Nerve Palsy

We report a case of multiple myeloma that presented as a fluctuating sixth cranial nerve palsy in the absence of widespread signs of systemic disease. A 63-year-old woman presented with horizontal diplopia of two weeks duration that subjectively changed over time. Ocular examination showed a fluctuating sixth nerve palsy. A computed tomography (CT) scan of the brain showed multiple, enhancing, soft tissue, mass-like lesions involving the left cavernous sinus and the apex of both petrous bones. Based on bone marrow biopsy and hematologic findings, she was diagnosed with multiple myeloma. Multiple myeloma may be included in the differential diagnosis of a fluctuating sixth nerve palsy, and although ophthalmic signs are rare and generally occur late in the course of multiple myeloma, they can still be its first signs.