Syringomyelia is a condition characterized by a fluid-filled cavity or cyst known as a syrinx that forms within the spinal cord. Syringomyelia is a chronic condition and a syrinx can expand over time compressing or destroying the surrounding nerve tissue. A wide variety of symptoms can potentially be associated with syringomyelia depending upon the size and exact location of the syrinx. Common signs/symptoms include pain in the neck and shoulders, muscle weakness, pain and stiffness in the legs, numbness or decreased sensation especially to hot and cold, abnormal curvature of the spine (scoliosis), muscle contractions, and uncoordinated movements (ataxia). The majority of cases of syringomyelia are associated with a complex brain abnormality known as a Chiari malformation. Additional known causes of syringomyelia include tethered cord syndrome, meningitis (arachnoiditis), certain tumors of the spinal cord, and trauma. In some cases, no underlying cause can be identified (idiopathic).
The terminology used in the medical literature to describe syringomyelia can be confusing. Syringomyelia is often associated with an abnormality of the craniovertebral junction, usually a Chiari malformation, and these cases may be referred to as congenital syringomyelia. Secondary syringomyelia refers to cases that have a known cause. The term primary syringomyelia has been used to refer to cases of unknown cause or to cases that occur because of specific known causes that damage the spinal cord. Posttraumatic syringomyelia refers to cases that result from trauma to the spinal cord (these cases are sometimes sub-classified as primary syringomyelia).
Some individuals have a condition related to syringomyelia known as hydro(syringo)myelia, which is characterized by abnormal widening of the central canal of the spinal cord (the normal small canal running through the center of the spinal cord). Some physicians use the terms syringomyelia or hydromyelia interchangeably. Hydromyelia may also be present in infants and young children with or without brain abnormalities, such as Chiari malformation type II. The fluid-filled cavities in cases of syringomyelia often do not connect to any other fluid-filled areas or spaces and occur more often in adults than children.