A 59-year-old woman in second remission of IgG, κ myeloma presented with confusion and nonlocalizing central neurologic and cerebellar signs. Magnetic resonance imaging showed meningeal enhancement. Lumbar puncture was atraumatic and revealed clear cerebrospinal fluid (CSF), an elevated protein content of 1.41g/L (normal < 0.45g/L), and a cell count of 0.1 × 109/L. The CSF cell differential revealed 76% plasma cells, 11% lymphocytes, 8% monocytes, 5% neutrophils, and no red cells. The plasma cells (panel A) were κ restricted. The CSF protein electrophoresis demonstrated IgG, κ chains (panel B). The albumin M-component ratio was ∼ 50% lower in CSF compared with serum. There were no plasma cells present in the peripheral blood smear. The presence of confusion, meningeal enhancement on MRI, and a clonal population of plasma cells in the CSF led to a diagnosis of meningeal myelomatosis. After a 28-day cycle of treatment with lenalidomide and dexamethasone, the confusion resolved and the plasma cells were no longer detectable in the CSF. Despite the remission of meningeal myelomatosis, she died with systemic myeloma 40 days later.

Mental confusion in myeloma is more commonly seen from renal failure, hypercalcaemia, infection, or hyperviscosity syndrome. In this patient's case, abnormal cognition was likely a consequence of meningeal myelomatosis. This is a rare complication of multiple myeloma and one with no well-defined treatment.

A 59-year-old woman in second remission of IgG, κ myeloma presented with confusion and nonlocalizing central neurologic and cerebellar signs. Magnetic resonance imaging showed meningeal enhancement. Lumbar puncture was atraumatic and revealed clear cerebrospinal fluid (CSF), an elevated protein content of 1.41g/L (normal < 0.45g/L), and a cell count of 0.1 × 109/L. The CSF cell differential revealed 76% plasma cells, 11% lymphocytes, 8% monocytes, 5% neutrophils, and no red cells. The plasma cells (panel A) were κ restricted. The CSF protein electrophoresis demonstrated IgG, κ chains (panel B). The albumin M-component ratio was ∼ 50% lower in CSF compared with serum. There were no plasma cells present in the peripheral blood smear. The presence of confusion, meningeal enhancement on MRI, and a clonal population of plasma cells in the CSF led to a diagnosis of meningeal myelomatosis. After a 28-day cycle of treatment with lenalidomide and dexamethasone, the confusion resolved and the plasma cells were no longer detectable in the CSF. Despite the remission of meningeal myelomatosis, she died with systemic myeloma 40 days later.

Mental confusion in myeloma is more commonly seen from renal failure, hypercalcaemia, infection, or hyperviscosity syndrome. In this patient's case, abnormal cognition was likely a consequence of meningeal myelomatosis. This is a rare complication of multiple myeloma and one with no well-defined treatment.

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