目的 通过高频超声探查上肢正中神经全程并熟练掌握正中神经的超声探查手法，选取超声易于辨识的解剖位点测量正中神经的横截面积（CSA）并探讨其与周围组织的关系，提供正常参考值范围并为临床诊断外周神经疾病提供依据。 方法 对240例健康志愿者沿正中神经走行进行高频超声探查，依次测量5个位点 ［腕管（腕横纹处）、前臂中点、正中神经穿出旋前圆肌处、肱骨髁上处及肱骨中点处］的CSA,每个位点重复测量３次取其均值，并进行CSA与身高、体重的相关性分析。 结果 高频超声显示，正常人正中神经横截面呈筛网状低回声图像，在不同部位分别显示为圆形、椭圆形或三角形，纵截面上成束状平行排列的低回声被断续的条带状高回声分割。探查得出，正中神经在上述5个位点的CSA均值以及双侧上肢之间同一位点处正中神经的CSA差异无统计学意义。 结论 正中神经在高频超声下全程可探及，显示率为100％；在不同部位的正常值及超声声像图略有差异，差异有统计学意义；正中神经的CSA在上臂段最粗，腕管处次之，前臂段最细。

Objective To depict the high-frequency ultrasound imaging of the median nerve of the upper limb in the normal living subject,master the median nerve scanning technique for the measurement of its cross-sectional area (CSA) at 5 easily-identified anatomical sites, reveal its relationship with surrounding tissues,and provide the reference range for clinical diagnosis of peripheral nerve diseases. Methods In 240 healthy volunteers, the CSA of the median nerve were measured by using high-frequency ultrasound at 5 sites which were the carpal tunnel ［rasceta］, forearm midpoint, the point where the nerve passed through the pronator teres, supracondylar humerus and at the midpoint of the humerus. At each site, the measurement was repeated 3 times. The average values of the measurements were analyzed for the correlation between the CSA and height and weight. Results High frequency ultrasound showed that the normal median nerve cross section appeared as a reticular low echo image in a round, oval or triangular shape, whereas its longitudinal section appeared as several parallel low echo bundles with intermittent banded echo segmentation.The CSA of the median nerve at these 5 loci were (10.67±0.94) mm², (10.25±0.61) mm², (9.83±0.50) mm², (11.44±0.43) mm², and (11.24±0.56) mm², respectively. There was statistical significance of the CSAs of the median nerve between humeral supracondylar humerus and the midpoint of the humerus and between men and women. Conclusion The display rate of the median nerve in the high-frequency ultrasound probe and the whole process is 100%. There are differences of the CSA in different parts of the median nerve. The CSA of the median nerve is thick in the upper arm and thin in the carpal tunnel and at the forearm.