Split spinal cord malformation (SSCM) is a rare form of spinal dysraphism in which a person is born with splitting, or duplication, of the spinal cord. It may be characterized by complete or incomplete division of the spinal cord, resulting in two 'hemicords.' There are two types of SSCM. In type I, each hemicord has a full protective covering (thecal sac) and they are separated by a bony structure, forming a double spinal canal. In type II, the two hemicords are surrounded by one thecal sac and there is a single spinal canal. While SSCM is present from birth, it may become apparent at any age and is more common in women than in men. Some people may not have symptoms, while others may have a tethered cord and/or various other spinal abnormalities. Symptoms vary and may include back pain, bladder dysfunction, and leg pain or weakness. SSCM is thought to be caused by abnormal formation of the notochord and neural tube (which ultimately form the brain and spinal cord) very early in embryonic development.