Clinical and Electrophysiological Characteristics of 23 French Patients With Neurolymphomatosis.

Introduction/aims: Neurolymphomatosis is a hematological condition defined by the direct infiltration of malignant lymphomatous cells into the peripheral nervous system. Since nerve conduction studies may disclose demyelinating features, clinicians may misdiagnose neurolymphomatosis as chronic inflammatory demyelinating polyneuropathy (CIDP). This study aimed to determine whether patients with neurolymphomatosis met the 2021 revised criteria for CIDP.

Methods: We retrospectively analyzed 23 patients with primary or secondary neurolymphomatosis from nine French hospitals. We analyzed whether patients with a diagnosis of neurolymphomatosis met the 2010 and 2021 CIDP criteria.

Results: 152 motor nerves were analyzed, and conduction blocks were found in 13.8% of them. Eight patients (34.7%) demonstrated at least one conduction block. Other demyelinating parameters fulfilling the 2021 CIDP criteria were rare, including reduced conduction velocities (1.7%), prolonged distal motor latencies (3%), absent F-waves (12.4%), and prolonged F-wave latencies (7.7%). Five patients met the 2010 CIDP criteria, whereas only one met the 2021 CIDP criteria.

Discussion: Demyelinating features are rare in neurolymphomatosis, and a conduction block is the most frequent abnormality. Consequently, only one patient met the 2021 criteria for CIDP diagnosis. This is likely attributable to the inclusion of sensory criteria. Furthermore, the new criteria emphasize the importance of identifying red flags, such as pain or monoclonal gammopathy, which could suggest an alternative diagnosis to CIDP. Clinicians should consider neurolymphomatosis in patients who present with red flags or atypical CIDP.