Ultrasonographic Normative Reference Values for Median Nerve Cross-Sectional Area in Healthy Nigerian Women of Reproductive Age

Background Ultrasonographic measurement of median nerve cross-sectional area (CSA) is widely used in the evaluation of carpal tunnel syndrome (CTS). Accurate interpretation requires population-specific normative reference values, which remain limited for African populations, particularly women. This study established ultrasonographic normative reference values for median nerve CSA in healthy Nigerian women of reproductive age and evaluated associations with selected anthropometric variables. Methods This prospective cross-sectional study included 165 healthy, asymptomatic, non-pregnant women aged 18–49 years. Bilateral median nerve CSA was measured using a 6–12 MHz high-resolution linear transducer at the carpal tunnel inlet (pisiform level) and 5 cm proximal to the distal wrist crease. Measurements were calculated using the ellipsoid formula, with three readings averaged per site. Paired t-tests assessed side-to-side differences, and Pearson correlation evaluated associations between CSA and age and body mass index (BMI). Statistical significance was set at p < 0.05. Results The mean age was 32.08 ± 6.73 years, and the mean BMI was 25.52 ± 5.24 kg/m². At the carpal tunnel inlet, mean CSA was 8.167 ± 2.650 mm² on the right and 7.837 ± 2.336 mm² on the left. Proximally, mean CSA was 6.562 ± 1.902 mm² on the right and 6.419 ± 2.142 mm² on the left. The mean side-to-side difference was 0.330 mm² at the carpal tunnel (t = 1.951, p = 0.053) and 0.211 mm² proximally (t = 1.368, p = 0.176). Weak negative correlations were observed between CSA and age (r = − 0.029, p = 0.609; proximal r = − 0.094, p = 0.092) and BMI (r = − 0.043, p = 0.437; proximal r = − 0.014, p = 0.808). Conclusion This study provides population-specific ultrasonographic normative reference values for median nerve CSA in Nigerian women, supporting accurate ultrasound-based evaluation of median nerve pathology in this population.