Hypomyelination Diseases

The speed of transmission of information from brain cells to brain cells and throughout the dog's nervous system depends upon whether nerves have developed myelin, a fatty protective sheath. Hypomyelination diseases manifest when myelin is present in insufficient amounts. These diseases occur in Chow Chow, Weimaraners, Samoyeds and Bernese Mountain Dogs. One form called the "shaking puppy syndrome," is a sex-linked recessive trait that affects only males.

The characteristic sign of hypomyelination is muscle tremors involving the limbs, trunk, head and eyes of newborn puppies. The tremors get worse with activity and disappear with sleep. Severely affected puppies show incoordinated body movements and are unable to stand. There is no cure for the disease, although tremors in Chow Chows and Weimaraners may improve gradually and disappear by one year of age.

In the recessive X-linked hypomyelination disorder of Springer Spaniels, a severe tremor is first seen in the second week of life in affected male dogs. These dogs are unable to stand or walk, and do not improve over time. Female carriers of this disease may have tremors which can resolve by 4-6 weeks of age.2 The conditions seen in Springer Spaniels and Samoyeds are lethal.3


  1. Debra M., DVM Eldredge, Liisa D., DVM Carlson, Delbert G., DVM Carlson, James M., MD Giffin, Beth Adelman. Dog Owner's Home Veterinary Handbook
  2. Curtis W. Dewey (editor). A Practical Guide to Canine and Feline Neurology
  3. Alexander De Lahunta, Eric Glass. Veterinary Neuroanatomy and Clinical Neurology