Study Evaluating the Predictive Value of the Terminal Latency Index (TLI) for Treatment Response in Patients With Anti-MAG Neuropathy

A Monocentric Retrospective Study Evaluating the Predictive Value of the Terminal Latency Index (TLI) for Treatment Response in Patients With Anti-MAG Neuropathy

"Anti-myelin-associated glycoprotein (anti-MAG) neuropathy is a rare dysimmune peripheral neuropathy, most commonly associated with an IgM monoclonal gammopathy. Its course is generally slow but may lead to significant functional disability. Despite therapeutic advances, including rituximab, intravenous immunoglobulins (IVIg), immunochemotherapy, and more recently Bruton tyrosine kinase inhibitors (BTKi), treatment response remains highly variable between patients. The Terminal Latency Index (TLI), an electrophysiological parameter reflecting distal demyelination, is a recognized diagnostic marker of anti-MAG neuropathy. However, its potential role as a predictive biomarker of treatment response remains insufficiently studied. Identifying a simple, reproducible, and readily available biomarker that could predict treatment response would be of major clinical importance for personalized patient management and optimization of therapeutic strategies. This monocentric retrospective study will analyze clinical, biological, and electrophysiological data from patients with anti-MAG neuropathy followed at Nice University Hospital (CHU de Nice) to assess the predictive value of baseline TLI for clinical response 12 months after treatment initiation."

Inclusion Criteria:

• Documented anti-MAG IgM polyneuropathy: positive anti-MAG antibodies, associated with an IgM monoclonal gammopathy, and a compatible clinical phenotype.
• Complete and interpretable baseline ENMG assessment: an initial electroneuromyography (ENMG) examination allowing reliable calculation of the TLI in at least two motor nerves among the right median, ulnar, and common fibular nerves.
• The examination must include the distal motor latency, proximal motor conduction velocity, and compound muscle action potential (CMAP).
• Treatment with at least one established therapeutic strategy: treatment initiated at the center, including intravenous immunoglobulins (IVIg), rituximab, immunochemotherapy, Bruton tyrosine kinase inhibitors (BTKi), and/or symptomatic treatment.
• Available functional clinical assessment: a documented INCAT disability score at two predefined time points: baseline (before treatment initiation) and 12 months (±2 months) after treatment initiation.
• Consent to participate in the study.

Exclusion Criteria:

• Peripheral neuropathy associated with an IgM monoclonal gammopathy, with strictly negative anti-MAG antibody testing or no available anti-MAG antibody measurement.
• Incomplete or uninterpretable ENMG data preventing accurate calculation of the TLI for the nerves of interest (median and ulnar nerves).
• Absence of a formally documented INCAT score at baseline or within the 12-month assessment window.