Syringomyelia is a condition that occurs when abnormal fluid collects inside the spinal cord. The cavity itself is called a syrinx. Syringomyelia does not always occur in patients with Chiari I Malformation.

Although the exact cause of syringomyelia is unknown, there are many theories about the formation of a syrinx cavity. One theory suggests that the herniated tonsils such as in the Chiari I Malformation results in blockage of the spinal fluid flow at the funnel-shaped are at the base of the skull that connects to the spinal canal. This blockage changes the fluid pressure around the spinal cord and causes fluid to accumulate in the spinal cord tissue. Spinal fluid pulsates with each heartbeat; coughing and sneezing cause even greater changes in the pressure inside the spinal canal. Other causes of syringomyelia are spinal trauma or the presence of a tumor.

Diagnosis of syringomyelia is best done through an MRI of the cervical and thoracic spine.

Treatment

The best treatment for syringomyelia is to remove the block to normal spinal fluid flow if there is one. In patients with syringomyelia due to the blockage caused by a Chiari I Malformation, the goal is to create more room at the foramen magnum (through a posterior fossa decompression). For many, the improved spinal fluid flow will result in the syrinx slowly decreasing in size, although it may not disappear completely. The important point is to keep the syrinx from growing and allow it to relax and decrease in size.

When syringomyelia is due to spinal trauma, release of the scar bands around the spinal cord can result in a decrease in the size of the syrinx. When it is due to a spinal cord tumor, the best treatment is usually removal of the tumor, if possible. When the cause of the syrinx is not known, the treatment decisions are more difficult. Some people may respond to sectioning the band at the end of the spinal cord, the filum terminale. If the syrinx is small and the symptoms are under control, observation and follow-up MRI scans are suggested.