Syringomyelia ("sear-ing-go-my-eelya") is simply a fluid-filled cavity of cerebralspinal fluid (CSF) in the spinal cord. This fluid filled sac, or cavity, is also known as a syrinx. This cavitation of the spinal cord is usually progressive and can cause neurological deterioration over time. In other words, until the underlying cause of the syrinx is fixed, it will continue to get larger and cause progressive damage to the nerves of the spinal cord.

The Chiari malformation is one of the leading cause of syringomyelia. There are also many other causes such as trauma. Many theories exist as to what causes the syrinx to form, however, none have conclusively been proven or universally accepted.

Most surgeons agree that the flow of CSF around the herniated tonsils must be restored in order to see the syrinx resolve, or collapse.