Abstract: Objective　To determine normal reference values for cross sectional area (CSA) and the correlation between demographic factors and CSA in the peripheral nerves and cervical roots using ultrasonography.　Methods　High-resolution ultrasonography of median, ulnar, tibial, fibular, C5, C6 nerves roots of one hundred healthy volunteers were explored. The CSA was measured and each measurement points was repeated for 3 times, and the average value was taken. The correlation between nerve CSA and age, height, weight and body mass index was evaluated.　Results　Bilateral nerve CSA tended to be symmetrical, with male nerve CSA larger than female nerve CSA. The peripheral nerves of the limbs were positively correlated with height, weight and body mass index, among which the correlation with body weight was the most significant. The CSA in mid-forearm of ulnar nerve, tibial nerve, C5 and C6 nerves root were positively correlated with age. There was no correlation between the difference of bilateral measurement sites and the above demographic characteristics.　Conclusions　This study provides normative values of CSA in the peripheral nerve roots of the limb and neck, which can be used as the reference criteria for the diagnosis of peripheral nervous diseases.

Key words: High-resolution ultrasonography, 　Peripheral nerve, 　Nerve root, 　Cross sectional area