Recurrence of B-cell Lymphoma Manifesting as Progressive Peripheral and Cranial Nerve Neuropathies: A Case Report.

Neurolymphomatosis (NL) is a rare neurological complication of lymphoma, characterised by direct infiltration of peripheral nerves by neoplastic cells. It most commonly occurs in association with non-Hodgkin's lymphoma (NHL) and poses significant diagnostic challenges due to its non-specific clinical presentation. Classically, NL presents as a painful, rapidly progressive, and asymmetric neuropathy, frequently mimicking inflammatory or vasculitic neuropathies. Here, we present the case of a 69-year-old woman with a history of NHL, in remission for five years, who presented with a progressive, asymmetric sensorimotor polyneuropathy that later progressed to include several cranial nerve palsies. Initial investigations demonstrated features of chronic inflammatory axonal polyneuropathy. The patient's atypical clinical progression and poor response to immunosuppressive therapy prompted further evaluation. A CT-guided sciatic nerve biopsy, based on fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging, facilitated the histopathological analysis that confirmed infiltration by malignant B lymphocytes, establishing a diagnosis of secondary NL. Targeted therapy with zanubrutinib led to marked neurological improvement, although she ultimately passed away. This case highlights the importance of maintaining a high index of suspicion for NL in patients with atypical or refractory neuropathies and a history of lymphoma and underscores the diagnostic value of FDG-PET imaging and nerve biopsy in guiding accurate diagnosis and delivery of crucial early intervention.