What is syringomyelia? And the malformation?
Syringomyelia (sir IN go my EEL ya), or SM, is a potentially painful condition caused by a skull malformation -- the Chiari-like malformation (CM), similar to the Chiari malformation in humans -- that makes the skull too small for the brain. CM often forces the brain to squeeze (herniate) through the opening into the spinal cord. This obstructs the cerebral spinal fluid (CSF) circulating around the brain and spine, causing pressure to rise, similar to placing a thumb over the nozzle of a garden hose. This turbulence can create pockets of fluid (syrinxes) in the spinal cord that press on nerves, which can cause pain and disability. There is no cure -- the aim of treatment is to alleviate pain.
Typical symptoms may include ONE, or SEVERAL, of these signs:
- excessive scratching, especially at ears, head, face, neck, shoulders
- 'air scratching' (the hind leg makes no body contact, typically when walking the dog)
- scoliosis (especially in young dogs), where the dog's neck and spine bend into a 'C'
- weakness in the legs
- pain, especially around the head, spine and/or legs
- sudden yelping for no reason
- flipping around to bite at the hindquarters
- allergies
- itchy ears
- spinal problems
Why is it appearing in cavaliers?
No one is really sure, but it is likely due to a small but widely affected gene pool (the breed was re-created in the 1920s). While CM/SM appears in small numbers in some other breeds, the vast majority of cases are cavaliers, though Brussels Griffons also appear to be significantly affected. In research samples, about 90% of cavaliers have CM, and 30% to 70% also have SM, though most do not seem to be symptomatic. Many researchers and breeders believe SM is now a leading health issue in the breed.
What causes CM/SM?
Researchers believe CM/SM is polygenetic -- carried on several different genes that have to combine in particular ways. CM/SM affects all four breed colours, and lines from all over the world. Puppies as young as 12 weeks have been diagnosed, and SM may affect a dog at any age, though more severely affected cavaliers tend to display symptoms before age four.
Tell me more...
This symptoms document lists some of the many possible symptoms (some dogs have several, some dogs have one, some are asymptomatic) and this page offers a step by step approach if you think your dog might have CM/SM. Also see Dr Clare Rusbridge's Canine Chiari-like Malformation and Syringomyelia, and download this podcast in which Dr Rusbridge offers an introduction to the condition.
This site also has video clips of affected cavaliers, tips on finding puppies, breeding advice, treatment advice, personal stories of people with affected cavaliers, information on MRIs and MRI images of affected dogs, details of low cost MRI clinics, lists of neurologists, information on past and current research, and links to related sites. A weblog here offers the latest news in the area of canine SM. You can also donate towards research into CM/SM.