Quantitative and morphological effects of age, body mass index, and sex on the peroneal nerve: A 3 tesla magnetic resonance imaging study

Purpose To characterize demographic variation in quantitative MR neurography parameters of the peroneal nerve and to assess the methodological impact of epineurium inclusion on signal intensity–based measurements. Materials and Methods This retrospective single-center study included 114 screened, presumably healthy subjects undergoing routine 3-T knee MRI. Cross-sectional area (CSA), signal intensity (SI), and nerve-to-muscle SI ratios of the peroneal nerve were measured at three predefined levels, with and without epineurium inclusion. Associations with age, body mass index (BMI), and sex were evaluated using univariable linear regression. Agreement between SI measurements with and without epineurium was assessed using cubic spline regression. Exploratory fuzzy c-means clustering was applied to visualize demographic trends. Results SI ratios measured with and without epineurium showed excellent agreement without evidence of a clinically relevant systematic bias. Increasing age was significantly associated with larger CSA ( p < .05). In contrast, SI ratios showed no significant age-related association and only weak trends. BMI demonstrated no significant association with either CSA or SI, and no relevant sex-related differences were observed. Fuzzy clustering corroborated regression findings, demonstrating gradual demographic trends with substantial overlap between clusters. Conclusion Quantitative MR neurography parameters of the peroneal nerve exhibit small, gradual variations with age and body mass index, primarily affecting cross-sectional area, while signal-intensity ratios remain largely stable. Measurements with and without epineurium inclusion show strong agreement, indicating that demographic-related variability is modest and should be interpreted as physiological variation rather than pathological change.