Syringomyelia is a neurological problem that arises as a result of a cavity (syrinx) forming and expanding in the spinal cord. The cavity frequently starts in the central canal of the cord and, for example, might be a tumor. As it expands, the first noticeable symptom might be a loss of pain and temperature sensation on both sides of the body several segments caudal to the cavity. Usually only one or two dermatomes are affected as the syrinx has affected only those anterolateral fibers that are in the act of crossing in the anterior white commissure which lies just anterior to the central canal. A belt-like analgesia (loss of pain) and thermal anesthesia results.