Sixth nerve palsy as a presenting sign of intracranial plasmacytoma and multiple myeloma.

Multiple myeloma and plasmacytoma are rare causes of mass lesions at the skull base and cavernous sinus. Sixth nerve palsy, in isolation or in combination with other cranial neuropathies, may occur rarely as the initial presenting feature of multiple myeloma. We report the neuro-ophthalmologic, radiologic, and pathologic findings for two patients who developed sixth nerve palsies as an initial manifestation of intracranial plasmacytoma and multiple myeloma. One patient presented with an isolated sixth nerve palsy in the setting of multiple vasculopathic risk factors. Treatable skull base lesions, including plasmacytoma and multiple myeloma, must be considered in patients with sixth nerve palsies, especially among those who demonstrate a progressive course or multiple cranial neuropathies.