Lymphoma causes various neurological manifestations that might affect any part of the nervous system and occur at any stage of the disease. The peripheral nervous system is one of the major constituents of the neurological involvement of lymphoma. In this study we characterized the clinical, electrophysiological and histopathological features of 32 patients with neuropathy associated with non-Hodgkin's lymphoma that were unrelated to complications resulting from treatment for lymphoma. Nine patients had pathologically-proven neurolymphomatosis with direct invasion of lymphoma cells into the peripheral nervous system. These patients showed lymphomatous cell invasion that was more prominent in the proximal portions of the nerve trunk and that induced demyelination without macrophage invasion and subsequent axonal degeneration in the portion distal from the demyelination site. Six other patients were also considered to have neurolymphomatosis because these patients showed positive signals along the peripheral nerve on fluorodeoxyglucose positron emission tomography imaging. Spontaneous pain can significantly disrupt daily activities, as frequently reported in patients diagnosed with neurolymphomatosis. In contrast, five patients were considered to have paraneoplastic neuropathy because primary peripheral nerve lesions were observed without the invasion of lymphomatous cells, with three patients showing features compatible with chronic inflammatory demyelinating polyneuropathy, one patient showing sensory ganglionopathy, and one patient showing vasculitic neuropathy. Of the other 12 patients, 10 presented with multiple mononeuropathies. These patients showed clinical and electrophysiological features similar to those of neurolymphomatosis rather than paraneoplastic neuropathy. Electrophysiological findings suggestive of demyelination were frequently observed, even in patients with neurolymphomatosis. Eleven of the 32 patients, including five patients with neurolymphomatosis, fulfilled the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic criteria of definite chronic inflammatory demyelinating polyneuropathy. Some of these patients, even those with neurolymphomatosis, responded initially to immunomodulatory treatments, including the administration of intravenous immunoglobulin and steroids. Patients with lymphoma exhibit various neuropathic patterns, but neurolymphomatosis is the major cause of neuropathy. Misdiagnoses of neurolymphomatosis as chronic inflammatory demyelinating polyneuropathy are frequent due to a presence of a demyelinating pattern and the initial response to immunomodulatory treatments. The possibility of the concomitance of lymphoma should be considered in various types of neuropathy, even if the diagnostic criteria of chronic inflammatory demyelinating polyneuropathy are met, particularly in patients complaining of pain.
Keywords: chronic inflammatory demyelinating polyneuropathy; demyelination; lymphoma; neurolymphomatosis; neuropathy.