The skull shape of toy dog breeds, such as chihuahuas and Cavalier King Charles Spaniels, is a significant risk factor for painful neurological conditions, reports a group of British and Canadian veterinarians.
Certain small dogs are predisposed to develop a condition called Chiari-like malformation, in which spinal fluid gets blocked where the skull connects to the spinal cord. This, in turn, can lead to syringomyelia, a painful formation of cysts form in a dog's spinal cord. 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 pup's skull.
Thomas Mitchell, a veterinary student at the University of Bristol in England, and his colleagues analyzed the shapes of 133 Cavalier King Charles Spaniels' noggins, and compared these measurements to the incidence of syringomyelia. They found that dogs with shorter snouts, in relation to the broadness of their skulls, and heads with forward-facing domes were at an increased likelihood of developing the neurologic disorder.