42.: Distal demyelinating neuropathy: Could it be neurolymphomatosis?

Lymphoma can affect virtually any organ system including the peripheral nervous system. Neuropathy associated with lymphoma may be secondary to direct invasion of lymphomatous cells (neurolymphomatosis), immune mechanisms, or as an adverse effect of chemotherapy or radiotherapy treatment. Establishing an accurate diagnosis is vital in order to initiate appropriate therapy, particularly in the case of neurolymphomatosis. Often determining the underlying pathological process is challenging as imaging and neurophysiological findings may be nonspecific. A 76-year-old man with diffuse large B-cell lymphoma presented with progressive asymmetrical muscle wasting, sensory loss and mild quadriparesis. Neurophysiology was consistent with a distal demyelinating sensorimotor neuropathy. Only minor enhancement of the right C8 nerve root was identified on MRI. In contrast, a whole body 18F-fluorodeoxyglucose (FDG) positron emission tomography(PET)-CT scan showed avid linear FDG uptake in the brachial plexus bilaterally as well as multiple other sites, consistent with neurolymphomatosis. There was also evidence of active lymphoma in other organs including the liver and pleura. On subsequent scans the FDG PET-CT scan was the most reliable means to determine treatment response. The neurophysiological features of lymphomatous infiltration of the peripheral nervous system were recently described. Features of demyelination were frequently observed and a third of pathologically proven neurolymphomatosis cases fulfilled the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic criteria for definite chronic inflammatory demyelinating polyneuropathy. This case highlights the sensitivity of FDG PET-CT scan in establishing a diagnosis of neurolymphomatosis because MRI and cerebrospinal fluid analysis are often unhelpful or non-diagnostic. This case also emphasises that neurolymphomatosis should be considered in demyelinating neuropathies associated with lymphoma even when there are minimal or no MRI changes.