Abstract
<jats:p xml:lang="tr">Introduction: Diabetes mellitus (DM) and rheumatoid arthritis (RA) affect the peripheral nervous system through distinct mechanisms, leading to polyneuropathy (PNP). This study compared nerve conduction studies in DM and RA patients, evaluating subgroups by PNP status. Methods: Electrophysiological examinations performed between 2015 and 2025 were retrospectively reviewed, including 208 DM and 96 RA patients. Motor and sensory conduction parameters of the median, ulnar, sural, and fibular nerves were assessed. Patients were classified as PNP+ or PNP–. Group differences were analyzed, risk factors identified with logistic regression, and significant parameters tested with ROC analysis. Results: In DM, conduction velocities were reduced, distal latencies prolonged, and amplitudes decreased (p<0.05). In RA, parameters were relatively preserved, with higher amplitudes than DM. Among PNP+ patients, DM showed more severe involvement; sural nerve velocity <34.5 m/s was discriminatory for DM (AUC=0.771; specificity 85.1%) from RA. In RA, PNP was mainly sensory and strongly associated with female sex (OR=7.51, 95% CI: 3.36–16.80). In PNP– patients, no major differences were found, though RA showed entrapment/demyelinating features and DM subclinical small fiber involvement. Conclusion: DM is characterized by widespread axonal degeneration, whereas RA presents heterogeneous and milder neuropathic patterns. These differences may aid differential diagnosis and prognostic evaluation. Sural nerve conduction velocity appears particularly promising as a biomarker</jats:p>