How Should Syringomyelia be Defined and Diagnosed?

OBJECTIVE: Syringomyelia is considered as a fluid-filled cavitation inside the spinal cord. However, there is no agreement whether a dilated central canal should be included under this heading or how glioependymal cysts, myelomalacias, or cystic tumors should be distinguished from syringomyelia. This article provides a definition of syringomyelia and guidelines for its diagnosis.
METHODS: Between 1991 and 2015, of 3206 patients with spinal cord pathologies 2276 demonstrated cystic features. All patients underwent magnetic resonance imaging. Syringomyelia was differentiated from cystic intramedullary tumors, glioependymal cysts, myelomalacias, and dilatations of the central canal by clinical and radiologic criteria.
RESULTS: A total of 1535 patients were diagnosed with syringomyelia, 635 with dilatations of the central canal, 52 with glioependymal cysts, 52 with mylomalacias, and 2 with cystic intramedullary spinal cord tumors. Additional neuroradiologic studies revealed the causes of syringomyelia. As a result 604 patients showed pathologies at the craniocervical junction leading to disturbances of cerebrospinal fluid (CSF) flow. The commonest was a Chiari I malformation in 543 patients. Nine hundred thirty-one patients presented with pathologies in the spinal canal. The commonest causes were spinal arachnopathies, leading to CSF flow obstructions in 533 patients, intramedullary tumors in 152 patients, and tethered cord syndromes in 69 patients.
CONCLUSIONS: The diagnosis of syringomyelia should be reserved for patients with a fluid-filled cavity in the spinal cord related to either a disturbance of CSF flow, spinal cord tethering, or an intramedullary tumor. For patients in whom such a relation cannot be established, the diagnosis of syringomyelia should be withheld.