Hypomyelinating neuropathy, also called hypomyelination, is a disease found in many mammals. The myelin sheath is a layer of fatty cells that covers each nerve in the body, including those in the brain and central nervous system. According to the Athabasca University Centre for Psychology, this sheath ensures that the electrical impulses that travel between nerves go where they need to. In hypomyelinating neuropathy, the myelin sheath is thinner than normal, making it difficult for nerve cells to communicate. Hypomyelinating neuropathy in dogs has a few specific symptoms.
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Tremors
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Tremors involving the whole body ("shaking puppy syndrome") are the most notable sign of hypomyelination, according to the Merck Veterinary Manual online. In a 1987 study published in the journal Acta Neuropathologica, J. N. Kornegay and colleagues reported a case of two Weimaraner puppies who developed tremors at three weeks old. Examination of the dogs showed that they had thinning of the myelin sheath in the brain and spinal cord.
Kornegay concluded that while there is no cure for tremors caused by hypomyelination, in some cases the condition can reverse itself. In one of the dogs he studied, the tremors gradually disappeared.
Curtis Dewey, author of "A Practical Guide to Canine and Feline Neurology," notes that not all tremors are caused by hypomyelination. Other causes are inflammation and viral infection. All tremors should be reported to your veterinarian as soon as you notice them.
Lack of Coordination
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In some dog breeds, including golden retrievers, hypomyelinating neuropathy manifests as a lack of coordination more profound than in most puppies. According to the Go Pets America website, puppies with the condition show poor control of their hind legs and tend to crouch in their rear quarters because of muscle weakness. Dogs with these symptoms will also tend to use a "bunny hopping" gait when they run, moving both hind legs forward together.
Bunny hopping is also common in dogs with hip dysplasia. Bunny hopping in your puppy or young dog is more likely to be a sign of hypomyelination than bunny hopping in a senior dog.
Early Onset
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The main way to distinguish hypomyelinating neuropathy from other disorders that can cause tremors, lack of coordination or muscle weakness is by noting the age of the dog when symptoms arise. According to the Merck Veterinary Manual online, heredity and in utero infection are the causes, so symptoms will show in the weeks after birth.
Symptoms in Different Breeds
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A survey of online articles about hypomyelination shows that some breeds of dog are more prone to the disorder. Bernese mountain dogs, chow chows, weimaraners, samoyeds and dalmatians are among these breeds. Springer spaniels are more likely to have hypomyelination of the central nervous system marked by gross tremor, as are weimaraners. Golden retrievers usually develop the peripheral nervous system form of the disease, which manifests as lack of coordination and muscle weakness.
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