Ultrasonographic measurement of cross-sectional area of the vagus nerve in patients with diabetic neuropathy: a systematic review and meta-analysis

Abstract

Introduction: Diabetic neuropathy, a prevalent complication of diabetes mellitus (DM), often involves autonomic dysfunction, with the vagus nerve (VN) being an early target. High-resolution ultrasonography has emerged as a noninvasive tool to assess structural nerve changes, including cross-sectional area (CSA), as a potential biomarker for early diagnosis. This systematic review and meta-analysis, the first to synthesize evidence on VN CSA in diabetic neuropathy, evaluated its diagnostic utility and confounding factors. Methods: Following PRISMA guidelines, a comprehensive search of PubMed, Scopus, Embase, and Web of Science yielded six studies encompassing 604 participants (347 diabetic patients and 257 controls). Results: Pooled CSA showed no significant differences between diabetic neuropathy patients and controls for left VN (MD: -0.02 mm(2), 95 CI: -0.80-0.75, P = 0.95) or right VN (MD: -0.39 mm(2), 95 CI: -1.09-0.31, P = 0.28). However, excluding an outlier study revealed a significant right VN CSA increase in DM patients (MD: 0.26 mm(2), P < 0.01). Subgroup analyses indicated significant CSA differences in patients with BMI <27 kg/m(2), age >50 years, and DM duration <9 years. Substantial heterogeneity (I-2 > 95) across studies underscores variability in ultrasound protocols and patient demographics. Discussion: While VN CSA alone may not suffice as a standalone diagnostic biomarker, its role in specific subgroups and combined with functional assessments warrants exploration. Standardized imaging protocols and longitudinal studies are needed to clarify its clinical utility and pathophysiological implications in diabetic autonomic neuropathy.