Cervical spondylosis has a wide range of symptoms, some of which may seem unrelated. For example, heart disorders and eye disorders occur, but there is a pattern among them. In general, cervical spondylosis has more symptoms in the neck and upper extremities, such as neck pain and stiffness, numbness and pain in the fingers, but a few patients with cervical spondylosis have no upper extremity symptoms but lower extremity symptoms first, even with urinary and fecal dysfunction. In the structure of the cervical spinal cord, the nerve fibers that innervate the movement and sensation of both lower limbs are arranged on its surface, while the nerve fibers that innervate the movement and sensation of the upper limbs are arranged in the central part of the spinal cord. These fibers are used to communicate with the brain and peripheral tissues and organs such as the limbs. Various sensory impulses from the extremities and trunk are transmitted to the brain through the upstream fibers in the spinal cord, causing the body to feel pain, warmth, cold or other sensations in a certain area. The nerve fiber bundles that travel downward then convey commands from the brain to govern various activities of the body. In cervical spondylosis, the superficial layer of the spinal cord is first irritated or compressed due to intervertebral instability. Repeated irritation and compression cause edema and even degeneration of the nerve fibers on the outer surface of the spinal cord, making its conduction function impaired. The outer superficial layer of the spinal cord is the motor and sensory conduction bundle of both lower limbs, and its dysfunction will lead to weakness, tendon reflex hyperactivity and numbness in both lower limbs; in severe cases, it may lead to paralysis of both lower limbs. The reason why the symptoms of bilateral upper limbs are more frequent in cervical spondylosis is that the nerve roots innervating the sensation and movement of bilateral upper limbs are easily stimulated by intervertebral instability, and when this pathological change develops further, eventually the cervical spinal canal is narrowed, the spinal cord has less room for movement, and its outer layer of nerve tissue is stimulated or compressed and clinical manifestations such as numbness and weakness of bilateral lower limbs appear.