Electrophysiological Phenotypes and Clinical–Metabolic Correlates of Neuropathy in Patients with Type 2 Diabetes Mellitus: An Original Cross-Sectional Study

Background: Diabetic peripheral neuropathy (DPN) is clinically and electro physiologically heterogeneous. Standard clinical screening scores and aggregate analysis frequently mask distinct metabolic profiles associated with isolated neurological patterns. We investigated the clinical-metabolic markers, vitamin B12 profiles, and diagnostic performance of bedside clinical scores across unique electrophysiological phenotypes in type 2 diabetes mellitus (T2DM). Material and Methods: An observational cross-sectional study of 80 participants with T2DM of >5 years' duration was conducted at SGT Medical College Hospital & Research Institute, Gurugram, India. Clinical assessments were conducted via the Diabetic Neuropathy Symptom Score (DNSS), Neuropathy Disability Score (NDS), and Neuropathic Pain Questionnaire (NPQ). Bilateral multi-nerve conduction studies (NCS) served as the standard gold benchmark. Abnormal electrophysiological findings were categorized into either generalized polyneuropathy-pattern or focal/other abnormalities. Results: Electrophysiological abnormalities were identified in 55/80 participants (68.8%), of whom 32 (40.0% of total cohort) exhibited a generalized polyneuropathy pattern and 23 (28.8%) presented with focal/other abnormalities. Within the electrophysiologically abnormal subset, participants with focal/other variants possessed highly elevated glycemic markers including HbA1c (9.21±0.44% vs 7.56±0.81%, p<0.001), fasting blood sugar (180.75±21.49 vs 139.41±28.02 mg/dL, p<0.001), and postprandial glucose (291.93±30.21 vs 228.03±33.46 mg/dL, p<0.001). Conversely, the generalized polyneuropathy subgroup exhibited significantly higher painful sensory burden on the NPQ (4.94±1.41 vs 3.30±1.94, p=0.001). Serum vitamin B12 concentrations were lower in the overall abnormal NCS group compared to neurophysiological controls (457.94±166.96 vs 592.41±129.34 pg/mL, p=0.00023). Against objective electrophysiology, the diagnostic sensitivity and specificity reached 100.0% and 96.0% for DNSS>=1, and 100.0% and 100.0% for NDS>=3. Conclusion: Diabetic neuropathy is highly heterogeneous. Distinct electrophysiological phenotypes display unique clinical and glycemic patterns. Poorer metabolic control strongly relates to localized focal lesions, whereas diffuse myelin/axonal stress yields a higher neuropathic pain burden. Pragmatic clinical screening programs must integrate phenotype-specific tracking with metabolic and vitamin B12 monitoring to guide clinical care.

Keywords: Diabetic Peripheral Neuropathy, Type 2 Diabetes Mellitus, Nerve Conduction Studies, Electrophysiological Phenotypes, Glycaemic Control, Glycated Hemoglobin, Neuropathic Pain, Vitamin B12, Neuropathy Disability Score, Diagnostic Accuracy.