Quantitative approach in assessing standard brachial plexus MRI for the diagnosis of multifocal motor neuropathy and Lewis–Sumner syndrome

Introduction. Among various chronic polyneuropathies, there are conditions that pose challenges for differential diagnosis: multifocal motor neuropathy (MMN) and Lewis–Sumner syndrome (LSS). The potential of magnetic resonance imaging (MRI) to objectively assess pathological changes in the nerve structures of brachial plexuses remains highly relevant for the diagnosis and differential diagnosis of MMN and LSS.

The aim of this study is to determine the diagnostic value of quantitative methods for assessing MRI signal intensity and thickness measurements of brachial plexus neural elements in differentiating LSS and MMN.

Materials and methods. The study included 59 patients: 26 diagnosed with MMN, 33 with LSS, along with 15 healthy volunteers.

Results. When comparing the combined patient group (regardless of diagnosis) with healthy controls, both nerve thickness and signal intensity coefficient were significantly higher in patients. Additionally, disease-specific threshold values for signal intensity coefficient were established for each condition.

Conclusion. The analysis of signal intensity coefficients LSS and MMN demonstrates that quantitative assessment of MRI signal intensity from the anterior rami of spinal nerves forming brachial plexuses provides additional diagnostic information about pathological changes and facilitates accurate diagnosis. This approach enables earlier initiation of pathogenetic therapy, reduces disability rates, and shortens the duration of patient incapacitation.