Excess cerebrospinal fluid in the central canal of the spinal cord is called hydromyelia. This term refers to increased cerebrospinal fluid that is contained within the ependyma of the central canal. When fluid dissects into the surrounding white matter forming a cystic cavity or syrinx, the term syringomyelia is applied. As these conditions coexist in the majority of cases, the term syringohydromyelia is applied