When Syringomyelia (SM), first started showing up in small breeds of dogs, in particular the Cavalier King Charles Spaniel, The Cavalier Club (UK) became involved in the research project to determine cause and mode of inheritance. Syringomyelia has been found to be in a number of breeds and can only be diagnosed by the dog undergoing an MRI scan. In basic terms Syringomyelia is caused by a pocket of accumulated fluid, called a syrinx (cyst) which forms in the spine at the base of the skull.
Here are some inks to information and research into Syringomyelia and Chiari Malformaiton in the Cavalier King Charles Spaniel.
http://www.cavaliers.co.uk/articles/SM bet hargreaves.htm