There may be several reasons for the pain in one side of the body: first, head diseases, when there is cerebral infarction, cerebral hemorrhage or tumor compression in the head, there can be pain and weakness in one side of the legs and arms, then the head MRI should be performed for early diagnosis and treatment; second, cervical spine diseases, when there is a tumor in the spinal cord of the cervical spine, there can also be pain and discomfort in one side of the legs and arms. Third, cervical spondylosis, when the cervical spondylosis is spinal cord cervical spondylosis, there can also be pain and discomfort in one side of the body, legs and arms.