Multiple myeloma (MM) is determined by the neoplastic proliferation of a single clone of plasma cells that produce a monoclonal immunoglobulin. One of the complications of this disease is central nervous system (CNS) involvement. In this study a 55-year-old male MM patient with headache and diplopia is reported.

In this study, a 55-year-old male MM patient with headache and diplopia due to skull base mass lesion near the clivus is presented as a rare presentation of MM.

Sixth nerve palsy alongside long tract lesion (presented with hand paresis and right-side hypoesthesia) in this patient might have been due to the compressive effects of the mass or ischemic lesions of the brainstem. Some of the rare complications of MM are ischemic stroke and cerebral infarction, which result from some conditions, especially hyperviscosity, in MM. On the other hand, hypercalcemia could be a cause of the weakness in these patients. Sixth nerve palsy in this patient could also have been due to amyloid infiltration or the mass effect.

One of the possible causes of acute diplopia in middle-aged patients could be metastatic lesions of the skull base. In this case, plasmacytoma of the clivus was the main cause of the disease.