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Editor,—Neurological complications are not uncommon in patients with multiple myeloma; however, an isolated intracranial plasmacytoma is rare. We describe a patient with multiple myelomatosis and a single intracranial lesion presenting with optic nerve compression.
A 73-year-old woman had had symptoms of intermittent blurring of vision in the right eye for several months and had consulted her optometrist, who had reassured her. She subsequently presented to her general practitioner with a 3 month history of left upper arm and right lower chest ‘rib’ pain, anorexia, weight loss, malaise, and fatigue. Skeletal survey revealed multiple extrapleural lesions bilaterally, with associated lytic bone destruction at each site. There was also evidence of lysis of the transverse process of T1 and facet complex of C7 on the right. She was referred urgently for further investigation.
On admission examination revealed no focal neurological deficit and investigation revealed hypercalcaemia (corrected calcium 2.80 mmol/l), raised serum protein (89 g/l), raised plasma viscosity (2.08 mPa), a venous IgG type κ paraprotein of 40 g/l, and a urine Bence-Jones monoclonal band of κ light chains of 0.34 g/l.
Abdominal ultrasound revealed two mass lesions in the anterior abdominal wall anterior to the liver. Bone scan showed multiple hot spots, especially in the posterior ribs and increased uptake in the sternum and left sacroiliac joint.
A diagnosis of multiple myeloma was made, the patient was rehydrated intravenously, and treated with intravenous steroids, melphalan, and radiotherapy. She was referred for ophthalmic assessment because of the history of blurred vision.
Best corrected visual acuity was found to be 6/60 N 14 right eye, 6/9 N 8 left (noted to be 6/9 in the right eye in 1986). A right relative afferent pupillary defect (RAPD) was detected and generalised constriction of the central 24-2 (Humphrey full threshold, Fig 1) with inferior altitudinal scotoma was noted on the right. There were minimal cortical lens opacities and funduscopy did not indicate any optic disc hyperaemia, swelling, or pallor. An urgent cranial magnetic resonance image was requested and this revealed a smoothly outlined mass in the right middle cranial fossa at the apex of the orbit compressing the optic nerve and enhancing with gadolinium (Fig 2); this mass appeared to arise from the dura mater and was the only intracranial mass detected. A diagnosis of intracranial plasmacytoma secondary to multiple myeloma was made and she was referred for radiotherapy to the lesion. Six weeks later visual acuity was 6/9 N5 right and left eyes, the right RAPD was barely detectable, and optic disc appearances remained normal.
Multiple myeloma accounts for 1% of all malignancies and 10% of haematological malignancies. Systemic signs and symptoms are due to pathological plasma cell proliferation, secondary metabolic alteration, and associated immunological dysfunction. Plasmacytomas are tumours comprising a proliferation of abnormal plasma cells; they demonstrate monoclonal intracellular immunoglobulins using immunological staining techniques, distinguishing them from plasma cell granulomas which show a polyclonal pattern of several different heavy and light chains.
Neurological complications in multiple myeloma were first classified by Clark1 into: (a) cranial nerve palsies; (b) intracranial tumour syndromes; and (c) intraorbital syndromes.
Intracranial tumour syndromes tend to present with multiple neurological symptoms and signs, occasionally with those of a space occupying lesion and raised intracranial pressure.
Intraorbital involvement commonly presents with optic neuropathy and this is usually secondary to direct infiltration, a retrobulbar tumour, or a hyperviscosity state.2 Optic neuropathy is rare secondary to an intracranial lesion and is usually associated with other neurological signs in these latter cases.2 Isolated optic nerve compression from an intracranial plasmacytoma with no other focal neurological signs has only rarely been reported in the literature as individual case reports.3 4 Two cases found in the literature were both initially treated as retrobulbar neuritis (RBN)—both with transient alleviation of symptoms with systemic steroid therapy; diagnosis was eventually made after a period of months by pneumoencephalography and craniotomy (in the absence of more sophisticated imaging techniques). A further case of intracranial plasmacytoma presenting with a long history of fluctuating vision and headache was treated as (biopsy unconfirmed) cranial arteritis with systemic steroids for 4½ years before diagnosis.2
Our case demonstrates a single intracranial deposit, and its magnetic resonance imaging appearance, resulting in an isolated optic neuropathy.
Magnetic resonance imaging is now the investigation of choice in patients with atypical optic neuropathies and no obvious orbital lesion.
Systemic agents—for example, melphalan, have little proved activity against intracranial lesions and extracorporeal radiotherapy remains the treatment of choice combined with chemotherapy for any systemic disease, as in this case.