What are the meanings of hydromyelia and syringomyelia?

Spinal cord fluid: Hydromelia means an abnormal collection of fluid within the spinal cord & connected to 4th ventricle within the brain and usually associated with hydrocephalus (xs fluid within the brain). Syringomyelia is also a collection of fluid, like an elongated cyst, in the center of the spinal cord itself, but does not communicate with any other fluid filled spaces, & can also lead to loss of nerve functio.

Spinal cord cavity: Hydromyelia refers to excess spinal fluid in the central canal of the spinal cord. Syringomyelia is when the spinal fluid dissects into the spinal cord causing a cavity (syrinx). These conditions coexist in the majority of cases- syringohydromyelia. All of these terms are often used interchangeably.