In anatomy, the upper trunk is located between the belly of the anterior and middle scalene muscles, and there is no basis for compression. However, the C5 and C6 nerve roots are surrounded by the crossed tendinous fibers of the anterior and middle scalene muscles at the intervertebral foramen, which is the basis for compression. Therefore, the author calls the upper trunk type thoracic outlet syndrome the C5 and C6 nerve root compression. In the past, it has been believed that the upper trunk type thoracic outlet syndrome is rare, accounting for only 4% to 10% of thoracic outlet syndrome. In fact, this disease is very common in clinical practice. The main reason is that this type of thoracic outlet syndrome is mistakenly classified as radiculopathy. The lesions of both are nerve root compression, and the compression sites only differ by a few millimeters to one or two centimeters, which is indeed difficult to distinguish clinically. With the in-depth study of cervical and shoulder pain, people have found that C5 and C6 nerve root compression can not only exist independently, but also be combined with C5 and C6 and C5 and C6 spinal cord compression type cervical spondylosis, and can also be combined with lower trunk type thoracic outlet syndrome.