A 48-year-old woman presented with intermittent horizontal diplopia without preceding trauma or significant past medical history. She had right sided retro-orbital pain. Clinical examination showed right abducens nerve palsy. Investigations showed elevated total protein and erythrocyte sedimentation rate, but all other biochemical investigations were normal. Serum protein electrophoresis showed elevated IgG and free kappa light chains, and skeletal survey showed lytic lesion at left fourth rib and multiple lytic lesions affecting the skull. Computed tomography scan of the brain showed enhancing soft tissue mass causing bony destruction of clivus and adjacent petrous temporal bone (fig 1), and magnetic resonance imaging showed extension into the cavernous sinus (fig 2), consistent with plasmacytoma. Bone marrow aspirate showed 65% plasma cells. The patient commenced treatment with dexamethasone, bortezomib and radiotherapy. She continues to do very well approximately 1 year since the diagnosis and the start of her treatment.

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Figure 1

Coronal non-contrast computed tomography scan (bony windows) showing soft tissue mass invading right side of clivus.

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Figure 2

Post-contrast coronal TI magnetic resonance image showing right cavernous sinus lesion.

Intracranial plasmacytoma is an uncommon manifestation of myeloma frequently associated with extension of a lesion affecting the clivus or skull base. There are rare case reports of myeloma presenting as an intracranial plasmacytoma1 and as cavernous sinus syndrome.2 Kyoda reported a patient with cavernous sinus syndrome (CSS) developing a number of years after diagnosis of myeloma with poor prognosis.3 This case highlights the need for good quality imaging focused on the cavernous sinus in all patients presenting with CSS, as well as screening for multiple myeloma.