Hydromyelia is often confused with a closely related condition, syringomyelia and sometimes these terms used are incorrectly used interchangeably. Hydromyelia occurs when cerebrospinal fluid accumulates within the central canal of the spinal cord. This creates a cavity which puts pressure on the nerve cells and causes the same symptomology as syringomyelia. Unlike syringomyelia, the fluid cavity is lined by ependymal cells. In contrast, a syrinx is a cystic cavity, usually secondary to a disection into surrounding white matter.