Analysis of the increase in cross-sectional area of the median nerve and its relation to age in neonates, infants and children using high-resolution ultrasound imaging.

AIM To analyze the increase in the cross-sectional area (CSA) of the median nerve during early childhood. METHOD This prospective, cross-sectional study used high-resolution ultrasound images of the median nerve from three locations (wrist, forearm and upper arm). A total of 43 participants (32 of whom were children younger than 2 years) were included in the study. RESULTS A strong and highly significant correlation was found between age and CSA (r = 0.8, p < 0.0001). The growth rate of CSA decreases with age. The increase in CSA follows a logarithmic growth curve (p < 0.0001). Based on the regression analysis, an age-synchronous increase in CSA for all three locations was found. The nerve reaches 70% of its final CSA by 2 years of age. INTERPRETATION Similar to the nerve conduction speed, the increase in CSA is greatest during the first 2 years of life. Then, the rate gradually and synchronously slows at the proximal and distal locations.