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| Syringomyelia
(SM) |
Mode of inheritance: unknown, likely polygenic Syringomyelia (SM) is a neurological condition similar to the human condition, Chiari Type 1 malformation or Arnold Chiari. This condition has only been recognised in recent years in dogs due to the development of the Magnetic Resonance Imagining (MRI) machine which allows a neurologist to identify the problem. It occurs in other breeds but is being studied by Dr. Clare Rusbridge, BVMS DipECVN MRCVS in the UK. In the Cavalier it is typically due to occipital hypoplasia which is a malformation of a bone at the back of the skull which is too small. This can displace the cerebellum forcing it into the foramen magnum, which is a small opening at the back of the skull leading into the vertebral canal which contains the spinal cord. CSF which is around the brain and spinal cord and normally moves freely through the foramen magnum becomes obstructed and accumulates in pockets known as syrinx which results in the condition, Syringomyelia. The most common symptoms of SM are an attempt to scratch at the shoulder or neck area but not make contact, especially when excited or on a lead. Sometimes the dog will attempt to walk and scratch at the same time. This behaviour is seen more frequently than would be natural for a dog with a skin or ear infection. The dog may also cry out or scream for no apparent reason. They may be more sensitive to around the head, neck and forelegs. Some severly affected young dogs may have a twisted or tilted neck position. Some dogs may show a wobbly rear end gait and others weakness in the forelegs. Though the symptoms may show up at any age generally they are seen between 6 months and 3 years.
There is only one way to positively diagnose the condition which is through the use of Magnetic Resonance Imaging (MRI), though due to the unavailability and high costs of this procedure many cases of Syringomyelia are diagnosed based on clinical symptoms. Treatment is usually surgical correction, though milder cases may have the symptoms controlled through the use of NSAIDS or corticosteroids. As of yet there are no firm statistics available for the incidence of this condition in the Cavalier. While it seems to be currently diagnosed in some numbers it may well be that, since this condition has only recently been recognised and there is now a way to diagnose it (MRI), that previously unexplained symptoms are being diagnosed as SM and this will level out. Though serious and devastating to the dogs affected and to the owners of affected dogs, the majority of Cavaliers are unlikely to have this condition. Implication for breeders Due to the unavailibility of MRI machines in many areas and the high costs it is not practical for breeders to have all their breeding stock tested at this time. In fact, as this condition is still in the early study stages not enough is known about the age of onset to allow us to know at what age or how often this test should be performed. Symptomatic dogs should either be MRI'd to rule out SM or pulled from a breeding program to avoid breeding affected dogs. However dogs showing no symptoms may still be carriers and the genes passed down to offspring. Dr. Rusbridge in the UK has undertaken a DNA study which includes Syringomyelia, Mitral Valve Disease and Epilepsy. Information on this study can be found at the Cavalier King Charles Spaniel Club, UK site at http://www.thecavalierclub.co.uk/ |
