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 a fatty substance around them (sheath) called myelin to protect them. 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.

Signs of Hypomyelination

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. Tremors in Chow Chows and Weimaraners may improve gradually and disappear by one year of age.

Hypomyelination of the peripheral nervous system has been described in Golden retriever littermates. In most clinical cases studied, signs appear in the first several weeks of age. Affected puppies have poor movement coordination of their hind legs, weak hocks which results in crouched appearance. Mild muscle atrophy and weakness is observed in dogs with a "bunny hopping" gait when they run.

References:
1. Dog Owner's Home Veterinary Handbook Debra M., DVM Eldredge, Liisa D., DVM Carlson, Delbert G., DVM Carlson, James M., MD Giffin, Beth Adelman