Research sheds new light on inherited dog disease
International study uncovers vital information about Chiari malformation – an unintended side effect of selective breeding that causes dogs to have brains that are too big for their skulls.
Chiari malformation affects many toy dog breeds which have been bred to have attractive baby–like heads, including the Cavalier King Charles spaniel, the Chihuahua and their crosses. Although Chiari malformation can be as asymptomatic, in many dogs it can cause headaches, problems with walking or even paralysis. The condition can also affect humans when certain skull bones fuse too early causing the cerebellar tonsils of the brain to descend through an opening in the base of the skull.
Dr Clare Rusbridge, Reader in Veterinary Neurology, has led a collaborative study with the University of Montreal and the University of Georgia which has identified the specific effect Chiari malformation has on the shape of a dog’s skull and brain.
The project saw researchers take 14 brain, skull and vertebrae measurements from 155 Griffon Bruxellois, a dog breed with a Chiari malformation prevalence rate of around 60%. By comparing the scans of affected dogs with normal dogs, they discovered that dogs with the condition had taller foreheads. The condition also caused the shape of the brain to change, with severely affected animals having their cerebellum pushed underneath the main part of the brain.
The findings from the team will be used in groundbreaking studies to identify which genes may be associated with the condition.
Dr Rusbridge, who is Chief of Neurology at Fitzpatrick Referrals alongside her research position within Surrey’s new School of Veterinary Medicine, said: “Chiari malformation can be described as trying to fit a big foot into a small shoe. It can be very painful, causing headaches and pressure on the brain and can result in fluid filled cavities in the spinal cord (a condition called syringomyelia).
“Our latest discoveries will be significant in driving this research forward. Our next steps will be to apply our technique to other breeds with Chiari malformation such as the Cavalier King Charles spaniel and Chihuahua. We also want investigate more sensitive ways of screening so that risk of disease can be detected easier, at an earlier age and with a single MRI scan.”
Many dedicated breeders MRI screen their dogs before breeding to maximise the chance of healthy pups. Currently, assessment is made by visual inspection of brain and spinal cord MRI. In the future, it is hoped that the wealth of expertise at the University of Surrey will lead to the development of more sophisticated imaging analysis.
Dr Rusbridge added: “We want to engage breeders and give them practical advice about the condition, but it’s also important to educate the public that breeding dogs in a certain way to influence how they look might not be in the animal’s best interest. You should also only buy them from people who have invested in screening and who are breeding for health as well as producing attractive puppies.”
The research was published in the journal PLOS ONE.
You can watch how the brain changes shape from a normal Griffon Bruxellois to one with Chiari malformation and Syringomyelia on YouTube.
Find out more about Veterinary Medicine and Science programmes and research at Surrey.