An MRI of a patient with syringomyelia. Note the long lighter colored area just below center, which is the cyst. Courtesy Cyborg Ninja, via Wikipedia
Syringomyelia is a condition caused by the growth of a cavity or cyst within the spinal cord. It can be congenital or acquired due to trauma, meningitis, bleeding, or a tumor. It generally causes neurological symptoms ranging from pain to numbness as well as unusual sensations.
When the spinal cord is enlarged, it inhibits the flow of cerebrospinal fluid around it, generally increasing pressure within the space. It's this pressure, rather than the enlargement itself, that causes the symptoms.
If suspected the cyst or cavity can usually be seen on a MRI, CT Scan, or myelogram.
Once diagnosed, the safest treatment is with painkillers. However, surgery is possible, but it has high risks as it usually involves manipulation of the spinal cord during surgery, risking further paralysis.
Syringomyelia is often caused by an Arnold-Chiari Malformation.