The Chihuahua has some predisposition to several neurological diseases, among them atlantoaxial instability, ceroid lipofuscinosis, congenital deafness, congenital hydrocephalus, muscular dystrophy, necrotizing meningoencephalitis and neuroaxonal dystrophy.: 3 In a radiographical study of canine periodontal disease in 2001, the Chihuahua was found to have the lowest incidence of any of the six ...