Peripheral Nerve Cross-Sectional Area in Healthy Thai Children: Reference Values for Clinical Neuromuscular Ultrasound

INTRODUCTION: Ultrasonography of the nerve cross-sectional area (CSA) is increasingly used to support the diagnosis of peripheral neuropathies. However, normative CSA reference values in children, particularly in Southeast Asian populations, are limited. METHODS: Ultrasonographic nerve CSA measurements were conducted in 164 healthy Thai children aged 1 to 18 years at King Chulalongkorn Memorial Hospital, Thailand. Participants were classified into six age groups. CSA was measured in 10 peripheral nerves at 34 anatomical sites and bilateral cervical roots (C5-C7), and the median CSAs were calculated. Correlations between CSA and body weight, height, and age were calculated using Spearman and Pearson correlation coefficients. Intraobserver and interobserver reliability were evaluated in a subset of participants using intraclass correlation coefficients. RESULTS: Normative CSA values were established for all examined nerves and sites. Most nerves demonstrated proximal-to-distal tapering in CSA, with the median nerve exhibiting a unique pattern of larger CSA at the wrist and mid-upper arm. C7 root was the largest cervical root measured (median CSA up to 7.0 mm2 in older adolescents). CSA demonstrated moderate-to-strong correlations with anthropometric variables, including weight, height, and age (r = 0.36-0.78). The tibial, sciatic, and median nerves showed the strongest correlations (all P < 0.001). Intraobserver and interobserver reliability were good-to-excellent across the selected nerves. CONCLUSIONS: Nerve CSA is influenced by age, weight, height, and location in this Southeast Asian population. These normative reference values may serve as a reference for distinguishing normal from pathological findings and aid clinical decision making in pediatric neurophysiological practice.