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X-linked Tremor, Congenital Tremor
Congenital problems associated with tremoring include hypomyelination, dysmyelination, and lysosomal storage disease. Males inherit an X chromosome from their mother and a Y chromosome from their father, while females inherit an X chromosome from each parent. In X-linked inheritance, the mother carries the defective gene on one of her X chromosomes and passes the disorder along to her sons.
Congenital tremors are due to defects of the protein myelin which covers parts of nerve cells (axons). These parts are responsible for transmitting nerve signals throughout the body. As a result of the defects, axons are either naked or surrounded by a disproportionately thin layer of myelin. The defect is confined to the central nervous system, while peripheral nerves are not affected.
Breeds at Risk
This group of disorders has been reported in many breeds of dogs. The condition is known to affect the Chow Chow,, Weimaraner, Bernese Mountain dog, Samoyed, Springer spaniel, and Dalmatian.
Signs of Congenital Tremor
Clinical signs appear within the first several weeks of age, however, cases of delayed onset also have been reported. In the recessive hypomyelination disorder of Springer spaniel dogs, a severe generalized tremor ("shaking pups") is first seen in the second week of life in affected male dogs. These dogs are much reduced in weight and size, unable to stand or walk, and do not improve over time.
Female carriers of the defective gene may have a milder form of the disease which resolves by 4-6 week of life. Dogs with this disorder may develop seizures as they mature. Affected dogs will often have resting tremor which worsens with exercise and excitement.
The Samoyed breed is affected with a hypomyelination disorder very similar to that of Springer spaniel dogs. Other breeds with this disorder seem to have less severe clinical signs than Samoyed and Springer spaniel dogs.
There is no treatment for this disease and in male Springer spaniels, there is no improvement over time. Chow Chows and Weimaraners have an unpredicatble prognosis and some may recover completely.
References
- Curtis W. Dewey, Anton G. Hoffman, Carol Rudowsky. A Practical Guide to Canine and Feline Neurology
- Alan A. Boulton, Glen B. Baker, Roger F. Butterworth. Animal Models of Neurological Disease: Neurodegenerative Diseases
- Shaking pups: a disorder of central myelination in the Spaniel dog. Part 1. Griffiths IR, Duncan ID, McCulloch M, Harvey MJ. Clinical, genetic and light-microscopical observations. In: J Neurol Sci. 1981 Jun;50(3):423-33
- Shaker Syndrome in a Cat. Chris Gordon. (Advisor: Dr. Scott Schatzberg; ecommons.library.cornell.edu)
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