When scalene muscle is the cause of pain, the pain is referred chest, inner lining
of scapula, shoulder, posterior and lateral sides
of the arm right up to the thumb and index finger. When this muscle shortens, this can press on brachial plexus and the subclavian artery and can compress or irritate these structures and cause symptoms such as abnormal sensation, cold extremity, claudication, and lymphedema in the involved extremity.