Date Published: 13 February 2014

Recent research into the effects of Chiari malformation on toy dog breeds

Health News from the United Kingdom (UK).

Chiari malformations in dogs* can cause headaches, mobility problems and in extreme cases even even paralysis. This condition in dogs, specifically of the Griffon Bruxellois breed, has been the subject of recent research at Surrey University in the south of England.

What is a Chiari malformation ?
Chiari malformations are structural defects in the cerebellum, which is the the part of the brain that controls balance. In normal healthy individuals the cerebellum, together with some parts of the brain stem, sits in an indented space at the lower rear of the skull above a funnel-like opening to the spinal canal called the foramen magnum. When, abnormally, part of the cerebellum is below the foramen magnum, it is called a Chiari malformation. This may occur when the bony space available is smaller than normal and so the cerebellum and brain stem are pushed downwards towards the foramen magnum and upper spinal canal.

The recent study, which has been published in the journal PLOS One (full ref. below), has identified the specific effect Chiari malformation has on the shape of a dog's skull and brain. Chiari malformation has become more prevalent as a result of selective breeding and affects many toy dog breeds which have been bred to look more doll-like, including Griffon Bruxellois, Cavalier King Charles Spaniels, Chihuahuas and their crosses.

The researchers took brain, skull and vertebrae measurements of 155 Griffon Bruxellois and compared dogs affected by the Chiari malformation, with 'normal' Griffons, i.e. those unaffected by Chiari malformation. Measurements revealed that Griffons affected by the condition had taller foreheads and that it had also caused the shape of the brain to change, with severely affected animals having their cerebellum pushed underneath the main part of the brain.

Although Chiari malformation can be asymptomatic, in many dogs it can cause headaches and other problems with walking or even paralysis. *It is also thought to affect approx. 1 in 1280 humans. Researchers at Surrey University are working with human geneticists at Montreal University in the hope that better understanding of the condition will lead to improved treatment for both dogs and humans.

Lead author, Dr Clare Rusbridge of Surrey University's 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. Our latest discoveries will be significant in driving this research forward and hopefully allow us to identify which genes may be associated with the condition. Our next steps will be to apply our technique to other breeds with Chiari malformation and investigate more sophisticated ways of screening, so that risk of disease can be detected more easily, at an earlier age and with a single MRI scan.
_ We want to engage breeders and give them practical advice about the condition, but it is also important that the public recognises that breeding dogs in a certain way to influence how they look might not be in the animal's best interest. There are responsible breeders out there, who have invested in screening and who are breeding for health as well as producing attractive puppies, and it is vital that people only look to buy from them.

Ref. to Paper:
Susan P. Knowler, 'Quantitative Analysis of Chiari-Like Malformation and Syringomyelia in the Griffon Bruxellois Dog' published in the journal PLOS ONE 12 Feb, 2014.

*Chiari malformation can occur in humans as well as in dogs but this research concerned the condition in dogs.

Source: University of Surrey, England (UK)

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