Comparative Neurology Program

Dandy-Walker Syndrome:
A cerebellar ataxia in Toy Fox Terrier dogs

What is Dandy-Walker syndrome?

Making a brain is hard work.  As a puppy's brain is forming in its mother’s uterus, a variety of signals ensure that each portion of the brain develops at the right time.  In the Dandy-Walker malformation, a portion of the cerebellum (the part of the brain responsible for coordination) doesn’t get the message to develop like it should.  The result is a shriveled up cerebellum that doesn’t function properly.  When the cerebellum does not develop like it should, the pup is left with problems with its coordination. It has a goose-stepping gait and may appear off balance. Affected pups may have other abnormalities, such as hydrocephalus (water on the brain) or blindness

What else causes ataxia?

Any disease that damages the cerebellum can cause ataxia that looks like Dandy-Walker Syndrome. Infectious diseases like canine distemper, some toxins, or other hereditary disease can all affect the cerebellum. Sometimes clues can be identified by a veterinarian that will point toward some other cause. The Dandy-Walker malformation can be seen readily on an MRI brain scan or if the pup must be euthanized, a post-mortem examination of the brain may provide a definitive answer

Pups with Dandy-Walker syndrome never walk normally. They have a goose-stepping gait & often appear off balance.

Is Dandy-Walker syndrome hereditary?

In children, Dandy-Walker Syndrome can either be hereditary, or caused from another disease such as an infection that affects the fetus during the wrong time in development.  Though it is too soon to say conclusively, Dandy-Walker Syndrome appears to be hereditary in the Toy Fox Terrier and is most likely a recessive trait.  In a recessive disease, both parents of an affected pup can appear normal.  All animals have two copies of each gene, one that is inherited from the mother and one that is inherited from the father.  A dog that has one normal gene and one gene that causes the disease is a carrier of the trait.  They show no symptoms because the one good gene is enough for their brain to develop normally, but they will pass that bad gene on to about half of their offspring.  If a carrier dog is bred to another carrier, then some of the pups (one quarter of them on average) will get a bad gene from each parent.  Without one good gene to carry the day, the cerebellum cannot develop normally and the unlucky pup has cerebellar ataxia. 

How do we find the gene responsible

The goal in dealing with hereditary diseases is to identify the gene responsible. Then we can develop a DNA test that will aid breeders in avoiding the disease in the future. Genes contain the genetic code that programs everything about an animal from the color of their coat to how their brains develop. Genetic disease occurs when a mutation interferes with the ability of a gene to function normally. Each dog has an estimated 20,000 individual genes, any one of which could contain a mutation that causes Dandy Walker Syndrome. We now have the tools, however, to find the mutation responsible for such diseases.

How can I help?

If you have a litter with a pup you believe might be affected, please contact us. We can help your veterinarian in determining whether or not this is the problem in your pup. In return, we would ask your help in collecting the samples and information necessary to continue searching for the gene responsible for this disease. Your continuing support will be necessary to achieve our goal.

Any information provided to us will be kept strictly confidential

As veterinarians, our first priority is to keep animals healthy. We also hope to learn things from our patients that can help children with similar diseases. You can learn more about Dandy-Walker syndrome in children at the Dandy-Walker Alliance website.

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In a normal brain (top) the area that coordinates movements is seen at the back of the brain (N). This area fails to develop in Dandy-Walker syndrome and is replaced by a cyst (dw in the image below).