Diastematomyelia, split-cord malformation (SCM), is a rare congenital abnormality in which there is partial or complete cleft in the spinal cord by a sagittal osseous or fibrous septum. It is seen predominantly in females, most often affecting the lower thoracic or upper lumbar segments. Clinically, diastematomyelia often presents as tethered cord syndrome (back pain, abnormal gait, spasticity, bowel / bladder incontinence) in children or young adults, although symptom onset may occur at any age. Patients may have a midline cutaneous abnormality such as a hairy patch or dimple over the affected area. There are two classifications:

• SCM type 1 consists of two hemicords, each with its own dural sheath, separated by a bony or cartilaginous septum.
• SCM type 2 consists of two hemicords within the same dural sheath but separated by a fibrous septum.