Beyond Nerve Size: The Role of Fascicular Architecture in Differentiating Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) From Other Demyelinating Polyneuropathies.

Introduction Nerve ultrasound contributes to the evaluation of inflammatory polyneuropathies, providing diagnostic support when clinical and electrodiagnostic (EDX) findings overlap. This study aims to evaluate cross-sectional area (CSA), echogenicity, and fascicular structure by ultrasound in patients with demyelinating polyneuropathy and identify features to differentiate chronic inflammatory demyelinating polyneuropathy (CIDP) from other conditions. Methods Fifteen patients meeting EDX criteria for demyelinating polyneuropathy were included. Bilateral median and ulnar nerves were assessed at five segments. CSA and architectural features-including fascicular pattern and echogenicity-were evaluated visually and quantitatively using ImageJ software (National Institutes of Health, Bethesda, MD, USA). Results The sample included 11 patients with CIDP and four with other demyelinating neuropathies (anti-MAG, multifocal motor neuropathy, and HIV-related vasculitic neuropathy). All patients exhibited nerve enlargement, particularly in proximal segments (axilla and humerus), with no significant CSA differences between groups (p > 0.05). However, CIDP patients showed a significantly higher number of nerve segments with loss of fascicular architecture (median 7.7 nerve segments) compared to other neuropathies (median 4.0 nerve segments; p = 0.033). An inverse correlation was observed between echogenicity and loss of fascicular pattern. Conclusions Although no significant differences in nerve CSA were found between the CIDP and non-CIDP groups, internal fascicular architectural changes provide potential clues for distinguishing these conditions. Assessing nerve microstructure, rather than size alone, may offer valuable diagnostic support in neuromuscular clinics.