Skull Shape of Toy Dog Breeds Linked to Brain Disease: Study

The skull shape of toy dog breeds, such as Chihuahuas and Cavalier King Charles Spaniels, is a significant risk factor for painful neurological diseases, according to a recent study.

Certain small dogs are predisposed to a condition called syringomyelia (SM), in which fluid-filled cavities, known as syrinxes, form in the spinal cord. This condition affects many popular toy breeds, including the Cavalier King Charles Spaniels (CKCS) and Chihuahua. But SM is usually secondary to a specific malformation of the skull called Chiari-like Malformation, or CM.

There's some debate about the underlying cause of canine Chiari malformations - but one significant factor, researchers write in the journal Canine Genetics and Epidemiology, is the shape of a dog's skull.

Researchers from the University of Bristol analyzed the head shape of 133 CKCS noggins, and compared their measurements to the incidence of syringomyelia. The results showed that dogs with shorter snouts, in relation to the broadness of their skulls (also known as brachycephaly), and heads with forward-facing domes were at an increased likelihood of developing the neurologic disorder.

"Our findings may allow breeders to select away from the condition over fewer generations by choosing appropriate matings and offspring to continue breeding programs," Thomas Mitchell, a veterinary student at the University of Bristol in England, said in a press release. "The identification of an appearance that might protect against developing the disease is a significant step forward in tackling this painful condition.

Mitchell's research is also a wake-up call to all dog breeders, who tend to select for certain appearances in dogs. However, moving slightly away from creating the perfect purebred dog may help in protecting certain breeds from diseases common among them.

"The study also provides guidance to breed clubs, breeders and judges that have a responsibility to avoid obvious conditions or exaggerations which would be harmful in any way to the health, welfare or soundness of the breed," Mitchell added.