Syringomelia is a rare (prevalence 8/100,000) chronic, progressive degenerative condition in which a tubular cavitation, called a syrinx (see MRI image, below left), develops within the central parenchyma of the spinal cord (below right). Although the syrinx usually develops in the lower cervical region, it may extend downwards in the thoracic or lumbar regions, or upwards into the medulla oblongata and pons (syringobulbia).

Almost 90% of syrinxes are associated with congenital Type 1 Arnold-Chiari Malformation, while an acquired syrinx may develop subsequent to spinal cord trauma, spinal arachnoiditis, and intramedullary cord tumours (astrocytoma, hemangioblastoma, ependymoma).