Unusual paraneoplastic neurological presentation associated with multiple myeloma.

Various neurological complications can occur in multiple myeloma. We report a unique paraneoplastic neurological presentation that led to a multiple myeloma diagnosis. A man in his mid-40s experienced a 6-month progressive decline in vision and gait. Examination demonstrated an upper motor neuron pattern, while MRI showed bilateral corticospinal tractopathy and optic neuropathy. Workup led to a diagnosis of multiple myeloma, while other causes (eg, primary central nervous system demyelination, toxic-metabolic, degenerative) were ruled out. Paraneoplastic antibody panels were negative. There was no evidence of leptomeningeal meningitis or compressive lesions. He significantly improved after multiple myeloma treatment. We attribute his unique presentation to a probable paraneoplastic syndrome given the temporal relationships to multiple myeloma diagnosis and treatment. Paraneoplastic neurological syndromes in haematological cancers are often not well-defined, thus requiring both a broad evaluation and awareness of potential connections.